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2023 | Buch


Proceedings of the Second International Conference on Sustainable Civil Engineering and Architecture

herausgegeben von: J. N. Reddy, Chien Ming Wang, Van Hai Luong, Anh Tuan Le

Verlag: Springer Nature Singapore

Buchreihe: Lecture Notes in Civil Engineering


Über dieses Buch

This book presents articles from the Second International Conference on Sustainable Civil Engineering and Architecture, held on 30 October 2021 in Ho Chi Minh City, Vietnam. The conference brings together international experts from both academia and industry to share their knowledge, expertise, to facilitate collaboration and improve cooperation in the field. The book highlights the latest advances in sustainable architecture and civil engineering, covering topics such as offshore structures, structural engineering, construction materials, and architecture.



Plenary Lectures

Floating Breakwaters: Sustainable Solution for Creating Sheltered Sea Space

This paper is concerned with floating breakwaters which provide a sustainable solution for creating a sheltered sea space from strong waves. We shall first present motivations for using floating breakwaters, their advantages and some example applications. This is followed by recent advances in materials, modelling, analysis and design of floating breakwaters, and recommendations for future research and developments.

C. M. Wang, H. P. Nguyen
Parameter Identification for Linear System Using Multiple Model Estimation

Kalman filter (KF) has gained wide adoption in system identification of engineering systems. It is a recursive estimation method under linear and Gaussian assumptions. In practice, a single model based on KF may not be able to capture the structural performance well for complex systems. To address this problem, KF estimation using multiple models is proposed. This method employs KF with different transition and measurement matrices, each of which can be assigned (if necessary) with different initial states, process and measurement noises to describe the system. The outputs of these models are then integrated to obtain the overall estimates through a weighted combination, where the weights are determined using the likelihood function. A numerical model is employed to illustrate the procedure and evaluate the accuracy of the proposed KF estimation with multiple models. The estimated results indicate that the proposed method is robust and reliable, with potential for system identification under a wider variety of situations.

Jixing Cao, Ser-Tong Quek

Architecture Session

An Adaptive Facade Configuration for Daylighting Toward Energy-Efficient: Case Study on High-Rise Office Building in HCMC

Natural daylight within buildings is one of the solutions to effectively reduce energy consumption in high-rise office buildings (HOB). The management of natural lighting depends largely on the characteristics of the building envelope (BE) in the building, especially the facade system. Adaptive facade (AF) is one of the solutions in the BE system of the building that helps to solve numerous problems in energy-efficiency and in particular, the balance of natural lighting. In this research, it is proposed that a kinematic AF system integrated onto the single-layer glass facade structure be implemented in HOBs in Ho Chi Minh City (HCMC), through the study of the typical case being the LIM Tower office building located in central HCMC. The kinetic AF system is integrated in order to improve the quality of natural lighting through 3 statistics: Annual Sunlight Exposure (ASE), spatial Daylight Autonomy (sDA), and Daylight Factor (DF). Results from simulations utilizing Rhinoceros-Grasshopper software (Computer-Aid Design) and Climate Studio plugin show that the AF phenotypes significantly reduce the luminance in the room—a reduction of appropriately 50% compared to the case without AF. In cases of the proposed AF phenotypes, the ASE index decreased below 10% compared to natural daylight conditions and achieved 3 points according to LEED V4.1. During the daily opening and closing cycle of the AF, the ASE and sDA indices don’t observe many sudden fluctuations and remained stable within the allowed lighting range.

Van Tung Nguyen, Thi Hong Na Le, Hung Tien Le, Phan Bao Long Nguyen
An Analysis of Architectural Features of Vietnamese Pagodas in an Giang Province

An Giang province is a potential rich place of spiritual tourism 310 pagodas. An Giang (AG) is considered one of the two provinces with the most pagodas in the Southwest cultural sub-region of Vietnam. This paper focuses on identifying architecture features and values in Vietnamese temples of AG province. Today, there are six typical pagodas in AG province, including An Hoa, Hoa Thanh, Linh Son, Phi Lai, Tay An and Ancient Tay An Pagoda. Architectural characteristics of AG pagoda can be codified from the construction site, master plan, layout, materials to be used for decorative and sculptural art. From that point, the tangible and intangible values in architecture of pagodas in AG province will be clarified. The results will be regarded as the basis for preserving and promoting the architectural values of pagodas in AG province in order to enhance activities of spiritual tourism in the local sustainable development plan.

Thi Hong Na Le
Asian Cultural Heritage Conservation: Cholon’s Heritage Resources in Vietnam’s Transformation

Saigon was founded by the army commander Nguyen Huu Canh in the seventeen century. It became the capital of the French colony of Cochin-China in 1883, part of French Indochinese Union which lasted until 1945, and the capital of the Republic of Vietnam (South Vietnam) until 1975. It has diverse cultural characteristics and a unique urban form. It was described as ‘the pearl of the Far East’, ‘the door to Far East Asia’, ‘the Oriental Paris’ (Guillaume, 1985) during the nineteenth and twentieth centuries. After the unification of the North and South Vietnam in 1975, Saigon was renamed Ho Chi Minh City (HCMC). Within the context of the ‘Asian Century’, Asia’s rapid growth and urbanization have transformed global commodity markets and Asian societies where millions of people have migrated from rural areas to the cities thereby increasing the urban population. The rapid transformation of HCMC’s economy in the last two decades is one of the success stories of Asia. The transformation of this economic Centre brought about tangible and intangible cultural changes at central places. A conservation plan has been drawn up in the past, such as Cholon town (2012), but this has not led to the conservation project to protect ‘the spirit’ of Saigon and Cholon, which had been considerably as the original cities in the past of HCMC. This paper, therefore, aims to re-assess cultural significance of old Cholon thematically to support action plans towards sustainable conservation in globalization context. It pays more attention to the district No. 5 as an important part of the inner city and is the location of many ancient historic places such as Gia Dinh region and Cholon (Chinatown), which date from the seventeen century and display characteristic architectural and urban features of the period. To deal with this issue, it is urgent that action is taken immediately to protect Ho Chi Minh City’s surviving built heritage.

Ngo Minh Hung
Assessment Framework of Urban Spatial Adaptability to Drought—Flood Coexistence (DFC). A Case Study from Phan Rang-Thap Cham City, Ninh Thuan Province, Vietnam

Measuring urban spatial adaptability to environmental stresses has recently been a popular topic in urban planning towards resilient cities. Urban Resilience has emerged over the past few decades across multiple dimensions from economics, society, environment, physics, and urban planning. Recently, many scholars in the planning have further investigated urban spatial Resilience to natural disasters and have stated that adaptive capacity is the critical factor to achieve Resilience. In Vietnam, the central provinces currently suffer from extreme climate events that cause heavy damage, such as droughts and floods. Ninh Thuan province, located in the South-Central Coast, at coordinates 11°18′14″ to 12°09′15″ Northern latitude, 108°09′08″ to 109°14′25″ Eastern longitude, is the typical place. The case study focuses on the capital city Phan Rang-Thap Cham City’s context—one of the most developed and vulnerable communities in the province of Ninh Thuan—to build an assessment framework of urban spatial adaptability to drought-flood coexistence (DFC). The framework consists of rows of urban spatial components and columns of adaptive indicators and variables to D.F.C. Urban spatial adaptability of Phan Rang-Thap Cham is measured by two methods. The first one is a qualitative analysis of urban spatial components, such as spatial networks and their land covers, based on adaptive variables to D.F.C. The second one is a quantitative analysis of the examined urban spaces interacting with the Remote Sensing (R.S.) index such as Normalized Different Vegetation Index (NDVI) and Land Surface Temperature (LST). Both of the two methods were carried out thanks to the utilities of R.S. and Geographic Information System (G.I.S.). The content of the study is reflected in four parts: (i) Overview of the concepts of urban spatial Resilience and adaptability, (ii) Study methodology and steps, (iii) Assessment framework of urban spatial adaptability to D.F.C., (iv) Conclusions.

Nguyen Quoc Vinh, Le Minh Ngoc, Le Anh Duc
Assessment of Sustainable Development in Phu Quy Island, Binh Thuan Province Using Sustainable Development Index

The objective of this study were to develop the sustainable development index (SDI) at the local scale and to investigate the sustainable level of sustainable development for the Phu Quy Island District in Binh Thuan Province. The indicators for the SDI were selected based on the literature review and expert consultation. The results identified 52 indicators based on 17 sustainable development goals (SDGs) for three components of sustainable development (i.e., economy, society, and environment) to estimate the SDI. Furthermore, the result of SDI for the Phu Quy District indicated that the level of sustainability is good. Also, the results highly emphasized increases in sex ratio at birth (SDG5), ratios of employment and product in processing and manufacturing industries (SDG13), and forestland area (SDG15) to improve the level sustainable development of the Phu Quy District.

Pham Viet Hai, Nguyen Thi Diem Thuy, Phan Thi Thanh Hang, Dao Nguyen Khoi
Assessment on the Economic Damage Due to Urban Inundation in Ho Chi Minh City

The most of urban objects living in coastal region as Ho Chi Minh City (HCMC) is adverse impacted by the inundation. Trading household is the important object of City’s economic and serious damaged by the inundation. They make a lot of jobs and a large workforce cooperating with them such as the distribution, business services. The trading households are not only adversely affected as the households (houses, yard, asset) but also damaged more such as the goods loss, revenues reduced, trade delayed,.. and hard living. It throughs the investigation and analysis by the SPSS model, the study determines of damage level to all citizen including the trading households and the flood-damage correlative function. Based on the research results, it shows that the economic damage of trading household object is more serious with the others in HCMC. With the research’s results (the tool on analysis and determination flood-damages), the district’s and city’s agencies will have a new tool to determine the damage level of objects including the trading household in their area. Through the assessment of flood-damage, the City assesses the effective of flood control methods.

Bui Viet Hung, Nguyen Ngoc Diep, Nguyen Viet Hung
Establishing the Water Body Planning Structure for Traditional Craft Villages of Hanoi City, with Thematic Study on Traditional Weaving Craft Village in Phung Xa Commune, My Duc District

Water bodies form a constituent part of the cultural values of traditional craft villages in Hanoi, Vietnam. Water bodies do not only improve the ecological environment and create landscape architecture but also preserve the traditional cultural values and support craft production activities in rural villages in Hanoi. Yet, urbanization and modernization of production has transformed villages and brought changes to the structure of water bodies there, as well as reduced their roles in the sustainable development of the craft villages. Through the survey in Phung Xa craft village (My Duc district, Hanoi), the article outlines the current situation of local water bodies and proposes solutions to establish the planning structure of water bodies in a way that will enhance their role and enable their potentials. The study results include viewpoints and principles to establish the planning structure, new functions, functional integration and structure of water bodies in craft villages.

Tuyen Van Nguyen, Hanh Thi My Phung, Huong Thu Nguyen, Thao Nguyen Phuong
Linking Dynamic Urban Settlement Patterns to Environmental Infrastructure Needs: The Case of Da Nang City, Vietnam

This paper outlines an urban structure type approach to interpret the interlinkages between sustainable infrastructure provision and the existing and evolving urban fabric of the Central Vietnamese city of Da Nang. Urban structure type mapping has become a widely used tool for categorising cities into homogenous areas for both planning and monitoring actions. The work investigates the relationships between the built environment and the spatial patterns of supporting infrastructure. Spatially mapped urban structure types and infrastructures provide a clear picture of Da Nang’s shortcomings and requirements towards strategizing effective cross-sectorial policy-making, planning and monitoring.

Nigel K. Downes
Model of Catlai Logistic Center—Ho Chi Minh City

Ho Chi Minh City aims to become the regional logistic center with the advantages of natural and social resources. According to the feasible study of logistic development, there are 07 logistic centers, distributed in the East–West-South-North of this city. In order to reach the goal that by 2025, it will trade 200 million tons of goods per year, Ho Chi Minh City needs to determine the appropriate paradigm for these logistic center and be ready to organize traffic corresponding to above mentioned volumes as well as consequent impacts to the spatial structure of the city.

Le Thi Bao Thu
Promote the Value of Planning and Landscape Architecture Under the French Colonial Period in Ba Vi National Park Towards Sustainable Tourism

Ba Vi Mountain offers a pleasant climate and a beautiful pristine landscape. Until the arrival of French colonists 90 years ago, the natural features and good environment of the Ba Vi mountain area were exploited for retreatment purpose. The environment and French architecture in the area have been devastated as a result of historical changes and neglect. Those ruins and landscapes must be repaired and developed in order to meet the necessities of current living. Later forest management legislation and tight land use restrictions, on the other hand, are limiting the growth of tourism services in the region. As an outcome, the research will actively contribute to our understanding of national culture, as well as educate young people about nature, social responsibility, and especially environmental conservation.

Nguyen Viet Huy, Nguyen Quoc Thong, Nguyen Duc Vinh, Pham Thuy Linh
Urban Infrastructure Issues: A Sustainable Alley Development and Construction in Viet Nam

The optimal planning and use of urban space aims to help solving problems of livelihood, spatial connectivity, increase living area and reducing air pollution. However, the challenges of rapid urbanization place a significant strain on the sustainable development of cities because the government is not prepared to invest heavily in every aspect or character of the city. Many studies have identified alley space as an important component in optimizing the network of urban spaces. Nonetheless, long-term sustainable solutions to alley infrastructure have been recognized as critical to city sustainable development in various literatures, but have been rarely applied in practice. This study examines the current state of alleys in Da Nang, Vietnam while proposing solutions to improve a typical alley space toward sustainable development, addressing environmental and urbanization issues.

Ngoc Thao Linh Dang, Ngoc Son Truong, Ngoc Toan Truong, Thi Tra Do
Urban Spatial Adaptability to Drought-Flood Coexistence (DFC). A Case Study from Phan Rang-Thap Cham City, Ninh Thuan Province, Vietnam

Since the Earth was gravely impaired by CC (Climate Change) in the past decades, a remarkable number of researchers have shifted their viewpoints regarding the city. They consider it a social system that gravitates towards a Social-Ecological System (SES). The very new concept of urban resilience focuses on the urban ability to recover from external shocks and attacks and bounce back to a new stable state, which helps narrow down the former broad concept of urban sustainability. Drought and flood are deemed overarching in Vietnam among the natural attacks, especially in Ninh Thuan province. This study, “Urban spatial adaptability to Drought-Flood Coexistence (DFC), a case study of Phan Rang-Thap Cham City, Ninh Thuan Province'’, aims to assess the city’s adaptability to not only grow, exploit and conserve during the attacks of local DFC but also to renew or self-organize its structure and functions after disturbances. During the study period of 1988 to 2020, the urban spatial adaptability to DFC of the examined area is qualitatively and quantitatively measured. Both urban spaces and the DFC of Phan rang-Thap Cham are investigated at interrelated urban scales, from macro to meso scales. The study covers four parts: (i) The concepts of urban spatial resilience and adaptability, (ii) The study methodology, (iii) The context of Phan Rang-Thap Cham City, Ninh Thuan province, and the study results, (iv) Conclusions.

Nguyen Quoc Vinh, Le Minh Ngoc, Nguyen Trong Khanh, Le Anh Duc

Construction Management Session

A Research on Quality Management of Feasibility Study Report: A Case Study of Mekong River Delta, Vietnam

Projects in Can Tho, one out of five biggest cities in Vietnam and becomes the most developed city in Mekong River Delta, that reach better outcomes usually derive from private sector whilst most of public projects are in the same patterns like lack of money, escalation in total cost investment, or even design changes during construction period. These issues are the typical wastefulness in public investment of Vietnamese construction industry. Many researches on the issues have been conducted but their research orientation has commonly focused on project implementation phase or closing phase rather than pre-construction phase. It is interesting to note that the three primary phases in a Vietnamese project life cycle are highly likely fit in the three phases in Juran Trilogy Diagram, namely quality planning, quality control and quality improvement. This also concludes that a lower quality of feasibility study report in preparation phase will result in a lot of wasted money in successional phases and vice versa. The overall aim of this research, therefore, is to improve quality in performance of the feasibility study reports of new construction projects for which public budgets are being allocated efficiently. The two main research objectives are to find out factors or attributes affecting quality management of feasibility study reports in public investment affairs of Group-B or higher projects and to integrate appropriately the so-called “best practice” feasibility study model from western countries into Vietnamese construction industry. Thanks to the most important factors, the research shall also develop a quality checklist to determine qualitative indicators of progressing activities as well as suggested to review or make appropriate decisions.

Ha-The-Cuong Truong, Han-Hisang Wang, Son-Ha Nguyen
Assessing the Effect of Design Risks on the Performance of Design-Build Projects in Vietnam

The design risk can have a significant impact on the success of design-build projects. Based on previous research presented by the authors on the identification of 21 design risks in the design-build projects in Vietnam, the design risk factors in design-build projects were classified into five groups: risk of inaccuracy or inadequate design information, inappropriate design risk, inappropriate designer's capacity risk, inappropriate contractor design capacity risk, risk of ambiguity project scale and scope of work. This study analyses the impact of design risks on project performance through three criteria: schedule, cost, and quality. Structural Equation Modelling (SEM) revealed that risk of improper design, risk of improper designer's capacity, risk of ambiguous project scale, and scope of work have a significant and negative impact on the project's performance. The result improves the understanding of design-build contractors to achieve better results thanks to better design risk management.

Thu Anh Nguyen, Vo Thi Dinh Khanh, Sy Tien Do, Phuoc Quy Dao, Truong-An Pham
Developing a Detailed Process to Quantify Risks on Variations of Project Time

The quantification of project time variations is important to project execution. However, so far, there has been still a lack of studies that focus on specific project schedules. Using structured and semi-structured interviews with contractors, this study develops a process in the planning phase of risk responses, which could help to assess the level of project time variations based on the impact of event chains. The application of the process is also illustrated using a case study, which is a part of the pre-validated actual project. The developed process could help to evaluate the precise impact of risk events with simple handling. The findings of this study could provide practitioners (e.g., project management teams) with a guideline to quantify the impact of risks on the dynamic levels of project time based on the analysis of the sensitivity chart of risk events. Hence, they could not only avoid the phenomena of excessive optimism and pessimism, but also allocate resources more appropriately during project implementation processes to reduce the unexpected impacts of risks.

Duc-Anh Le, Long Le-Hoai, Chau Ngoc Dang
Development of Novel Hybrid Artificial Intelligent Model for Optimizing Material Supply Chain in Construction Projects

On the construction site, the time is rushed so the managers are only concerned about human resources and construction methods to meet the schedule, while paying little attention to construction materials. Because of the lack of concern about material costs, the current cost management of managers is still not really effective. Therefore, this study proposes to use a novel Hybrid Artificial Intelligent Model (HAIM) to optimize the material supply chain save cost for construction contractors. The construction logistics planning method is utilized to find suitable material requirements as well as control the cost of construction materials. The validation analysis shows the advanced searchability of proposed model to traditional and model metaheuristic algorithms. Using HAIM, Managers can optimize construction costs through material demand planning; thereby increasing profits for the project and the company will increase its competitiveness in the construction market.

Vu Hong Son Pham, Huynh Chi Duy Nguyen
Enhancing Building with Adaptive Design Objects Using Building Information Modelling Towards Consuming Energy Efficacy in Building

Energy consumption in buildings is an important factor in the design and operation of a project as if energy reduction used in a building helps to lower operating costs and its environmental impact. Optimizing architectural design options, building surfaces, and HVAC systems from the beginning of a project using Building Information Modeling (BIM) to reduce energy consumption in the building is a new trend nowadays. BIM is said to be an interactive environment that efficiently manages and analyzes elements related to architecture, structure, electricity, and water design as well as the construction process. Furthermore, there are a variety of building energy modeling (BEM) tools that can import these BIM files and perform energy simulation. The simulation and calculation of the energy model via BIM, in particular, is regarded as a new solution for the construction industry in the future. In this research, energy simulation in buildings using a BIM system is proposed to change those design elements within construction process in order to reduce the Energy Use Intensity (EUI) and energy cost in the building. The result of this research are expected to help architects and building managers improving and enhancing the efficiency of energy used in buildings.

Ngoc Son Truong, Duc Long Luong, Ngoc Tri Ngo, Quang-Trung Nguyen, Ngoc Thao Linh Dang
Error Assessment of Point Cloud and BIM Models to Actual Works

3D Laser Scanning technology is being widely applied in the construction industry 4.0 for promoting the digitalizing and BIM modeling procedure, also called Scan-to-BIM. Scan-to-BIM technology helps to capture the continuously existing condition of the project and construct a BIM model in just a short period of time, also, update and store the data of the project throughout construction stages. Scan-to-BIM technology could, however, entail many risks if the users cannot control the errors of the point cloud model and BIM model. Although point cloud collected by 3D laser scanners has high accuracy, there are mistakes during Scan-to-BIM process, which cause errors. Therefore, the 3D BIM model based on the point cloud contains errors of dimension, coordinate, position, and these errors could cause difficulties for construction project management engineers and make the BIM model meaningless. This paper presents the causes of the errors, also analyzes and evaluates the errors of Scan-to-BIM process by the methodology of comparing point cloud and BIM models with physical objects to control the errors and support the next step of using the VR, AR, and MR. The data used in the paper is obtained from a real project which applies Scan-to-BIM technology to verify the theory.

Sy Tien Do, Hiep Hoang, Dat Ho Quang Che
Factors Affecting Employee Retention in Construction: Empirical Study in the Mekong Delta Region

Together with the whole country, the construction industry in the Mekong Delta region (in the South of Vietnam) is developing very fast. However, this region faces more difficult challenges in attracting qualified labor forces than other areas. To meet the region’s needs, there should be coordination between management units, training units, investors, and construction organizations to provide strategies to attract more construction employees. Using a questionnaire which includes 36 potential factors regarding the retention of employees in construction, 160 responses were collected from different organizations in the Mekong Delta region. The results indicated several important factors which could affect employee retention such as base salary, salary payment term, labor contract, labor market mobility, and opportunities to participate in large construction projects. Using factor analysis, this study also identified eight main influential constructs of employee retention in the Mekong Delta area’s construction fields, namely organizational conditions and policies (C1), motivation (C2), working environment (C3), demanding (C4), income (C5), job opportunities (C6), welfare (C7), and job nature (C8). The findings of this study could provide useful information about how to develop and attract qualified human resources in the Mekong Delta region, as well as other similar areas in other developing countries.

Duc-Anh Le, Long Le-Hoai, Van H. Le, Chau Ngoc Dang
Identifying Stakeholder’s Behavioral Intentions of Applying BIM to Construction Projects in Vietnam

Nowadays, industrial revolution 4.0 is taking place firmly and affecting many industries and fields. In construction, some new technologies have been developed and applied to the design, construction and management. Building Information Modeling (BIM) is a digital environment that allows stakeholders to quickly share and update project lifecycle information across 3D models containing data. BIM is increasingly being applied in construction projects. However, the results of applying BIM for construction projects in Vietnam are still limited. This study combines the Theory of Planned Behavior (TPB) and the Technology Acceptance Model (TAM) to exploit and explain the stakeholder’s behavioral intention when applying BIM to construction projects in Vietnam. Descriptive statistics, Cronbach’s Alpha reliability analysis and Correlation analysis with SPSS were used in this study. The results provide proper solutions to raise awareness about the importance of applying BIM among stakeholders in the construction industry in Vietnam through seminars, training, or workshops.

Thi-Thao-Nguyen Nguyen, Thu Anh Nguyen, Sy Tien Do
Implementation of BIM and High Technology in Project Life Cycle

Building Information Modelling (BIM) has made a considerable contribution over the past few decades regarding information technology applied in the construction industry. Recently, the fourth industrial revolution brings about the tendency toward digital twins when physical objects are digitalized beside the BIM model integrated with Hi-Tech for the digital twin future. The boom in benefits that successfully apply future applications to different phases of the project’s life cycle is spread through the application of superior technologies such as BIM 4D construction simulation; BIM 5D controls costs; H-BIM Historic Building Information Modelling, 3D Laser Scanning; Virtual and Augmented Reality applications from design to construction. This paper summarizes the integration of construction 4.0’s critical components over the project life-cycle concentrated on three main phases of a standard project.

Thu Anh Nguyen, Truong-An Pham
Integration of H-BIM, Virtual Reality, and Augmented Reality in Digital Twin Era - A Case Study in Cultural Heritage

This research has digitized the 100-year-old Hung King Temple in Ho Chi Minh City, Vietnam, for heritage conservation and tourism promotion. H-BIM and 3D laser digitization is regarded as a steppingstone toward heritage preservation. While laser scanning allows surveyors to identify complex existing geometries with great precision in a short period, BIM reserves the information model for future operations and maintenance. Scan-to-HBIM has emerged as a game-changing technology for transferring data to a digital module and processing it to create spatial objects. Tourism is becoming more interested in Virtual Reality (VR) and Augmented Reality (AR). Travel involvement in VR technology is an unavoidable direction to catch up with the development of tourism. These integrations are assisting in ushering in the future Digital Twin city era. This study focuses on clarifying the integration of Hi-Tech, such as VR, AR into H-BIM point cloud model for the virtual public show, in which the Temple of King Hung is chosen for the case study. A new approach involving VR and AR vision algorithms is also presented to promote the city’s value by promoting digital tourism, making valuable cultural heritage and tourism accessible through technology.

Thu Anh Nguyen, Sy Tien Do, Truong-An Pham, Dai Huu Nguyen, Hiroshi Tamura
Multi-objective Optimization of Time—Cost—Environmental Impacts in Roadway Construction Projects: A Case Study in Vietnam

Greenhouse gas emissions (GHGs) have become and are becoming an important environmental issue in all industries worldwide. The construction industry has also begun to consider evaluating greenhouse gas emissions to assess the viability and prioritization of projects in a sustainable manner. The creation of emissions during the construction stage of roadway projects is mainly due to the use of fossil fuels for the operation of construction machinery. Therefore, the need for research on the efficiency of using equipment in the transport construction towards reducing the environmental impact is increasingly urgent. The main objective of this study is to analyze and propose solutions for the time - cost - GHGs emission optimization problem. The research process will go through four main parts as follows: The first is the literature review; Next is the development of analytical model; Then is solving the problem by a multi-objective optimization algorithm; The final is discussing on results and delivering the conclusions. Data from the National Highway No.20 through Lam Dong Province will be used as a case study.

Truc Thi Minh Huynh, Trung-Viet Tran, Anh-Duc Pham
Novel Tendering Perspective for Encouraging Bidder Effort in PPP Projects

For PPP projects, the lowest price is not the top criteria for bidding winning, instead, the quality issue is a leading concern by the employer or government. Thus, contractors need to spend a lot of effort and expense in the bidding stage to balance profitability and quality, in order to reduce incurring costs in the construction phase. Encouraging high effort of the tenderer in the procurement stage is a critical problem based on the owner's perspective. Whereas, bid compensation is one of the suggestions which should be analyzed the feasibility in many scenarios. In this paper, the objective is to assess how to use effectively bid compensation in a particular case that has involving the owner, strong contractor, and normal contractor. Game-theoretic is applied to set up the modeling concept of bid compensation, as well as, explain strategic interaction between players. To solve the model is to solve the Nash Equilibrium solution. For purposes, this research should compare among models with the increasing number of bidders to provide the effectiveness of the bid compensation decision by the owner. Moreover, it will also be measured the weight of bid compensation amount that impacts to depth investing of bidder’s choice.

Vu Hong Son Pham, Kim Anh Phan
Proposing the Performance Assessment Model for Coastal Projects in Vietnam Toward Sustainable Development

Today, coastal construction project is one of the types of projects attracting a lot of domestic and foreign investment capital in the coastal regions of Vietnam. However, apart from the qualified projects, there are also many coastal projects having poor quality, failing to meet the requirements, encountering risks, facing problems affecting environmental pollution, causing coastal erosion, changing marine geological strata, or more seriously, there may be problems related to occupational safety, human life. It is necessary to propose a model to evaluate the performances of coastal construction projects, from which this study will come up with measures to solve and improve the efficiency of these projects. Important criteria in evaluating the performances of coastal projects are investigated using Exploratory Factor Analysis (EFA) method. The Importance Performance Analysis (IPA) method is utilized to identify those attributes of coastal projects that are most in need of improvement or that are candidates for possible cost-saving conditions without significant detriment to overall quality.

Ngan-Hanh Pham-Nguyen, Truc Thi Minh Huynh, Minh-Huy Nguyen
Simulation of Vessel Collision Scenario Using Photogrammetry and 3D Laser Scanning-A Case Study at the Container Terminal

Currently, transportation on the waterway in Vietnam is being increased considerably to meet the booming economy’s demand. There are many river ports and seaports constructed within the two initial decades of the twenty-first century. The comprehensive studies of the ports system planning, hydrodynamic model for the channels were studied. However, specific research, such as inspection work after vessel collision is not yet fully estimated. This paper presents a study on the vessel collision of a container terminal located in Southern Vietnam. The inspection work was carried out by using innovative survey technologies, namely, 3D laser scanning, and photogrammetry. The simple-to-use process for simulation of vessel collision was then proposed. The evaluation and testing of structural components and operating equipment will then be performed meticulously.

Sy Tien Do, Hiep Hoang, Nhan Nguyen Trong Truong, Dat Ho Quang Che

Construction Material Session

Activation of Nanoparticle and Alkaline Environment on Fly Ash Geopolymer Mortar

The goal of this study is to evaluate the influences of nanoparticles on the mechanical property of fly ash geopolymer mortars. The nano-silica (NS) and nano-alumina (NA) were added to geopolymer mortar with a various amount of nanoparticle-to-fly ash in range from 5 to 25% by weight, respectively. In this research, the different NS/NA ratios in range from 0.5 to 2, by weight, were investigated. For the geopolymerization process, the alkaline solutions (AS) including sodium hydroxide (SH) and sodium silicate solution (SS) were mixed with the SH/SS ratio of 1, by weight. The different ratios of alkaline liquid to fly ash in range from 0.4 to 0.6, by weight, were investigated. The results were focused on the geopolymerization between nanoparticles and alumino-silicate resource by strength in ambient temperature condition. The compressive strength of geopolymer mortar can be up to 22.62 MPa. The suitable mix proportion can be obtained by amount of 5% nanoparticle by fly ash weight, a ratio of NS/NA as 0.5, and ratio of AS/FA as 0.5, by weight, respectively.

Tan No Nguyen, Huu Quoc Phong Le, Anh Tuan Le
An Evaluation of Chloride Ion Penetration of Reinforced Concrete with Surface Coating Materials Exposed for 25 Years Under Coastal Environments

In this study, reinforced concrete specimens with three surface coating materials were exposed to a coastal environment for 25 years to investigate their long-term durability and salt penetration control effect. The specimens were fabricated simultaneously and analyzed at 4.8 years and eight years. The exposure tests are conducted in the coastal area of Hokkaido, in northern Japan, at 40 m from the coastline, and the annual chloride ion flux is 7.1 mg/dm2/day on the seaward side of specimens. Chloride ions that penetrated the concrete are analyzed by potentiometric titration to determine the number of chloride ions and the penetration depth. We compared the amount of chloride ion penetrating to each material used for repairing and coating. The change in the shielding effect of the surface coating materials is also determined based on the change over time from the past experimental results. As a result, the coating material S (multi-layer textured coat) has the most practical effect on preventing chloride ion penetration.

Sachie Sato, Masaru Kakegawa, Yoshihiro Masuda
Applicability of Electrical Resistance Method to Moisture Transfer Measurement in Paste Using Mineral Admixture

Concrete is a porous material which has the ability to hold moisture stably inside. Since moisture is closely related to the deterioration of concrete structures, it is important to understand the moisture transfer in concrete in order to maintain the concrete structure appropriately. The electrical resistance method is one of non-destructive methods to investigate the moisture in concrete and the moisture transfer can be assessed with time by using one specimen. However, the electrical resistance may be affected by mineral admixtures in concrete. Although previous studies on the effects of mineral admixtures on the electrical resistance have been conducted, there are still many unclear points. Therefore, the purpose of this study is to assess the applicability of the electrical resistance method to moisture transfer measurement in paste containing mineral admixtures by focusing on the moisture transfer in the drying process. The moisture transfer in the hardened cement paste using fly ash and blast furnace slag with water-to-binder ratios of 0.35 and 0.55 was investigated by the electrical resistance method. Stainless steel rods of 0.9 mm in diameter were placed at an interval of 4 mm in the specimen. The calibration test was also conducted to obtain the relationship between the electrical resistivity and the internal relative humidity of the specimen. The result showed that the specific resistance of the specimen containing mineral admixtures was higher than that of the specimen without mineral admixtures. It was observed that at the drying period of 70 days, the internal relative humidity at a depth of 4 mm from the exposed surface was almost the same as the surrounding relative humidity. It is possible to know the change in the internal relative humidity distribution in the cement paste using mineral admixtures during the drying process by performing the calibration test appropriately.

Takahiro Aoki, Yuko Ogawa, Kenji Kawai
Application of Recycled Fine Aggregate from Construction and Demolition Materials for Mortar

Construction and demolition materials are collected during the process of constructing and demolishing buildings. These materials are a major solid waste stream in Vietnam, with a relatively large amount released every year. In this study, the waste materials such as concrete, mortar, bricks, and ceramic tile are investigated to use as recycled fine aggregates (RFA) in mortar. Several tests were conducted to determine fineness modulus, porosity, flow, setting time, and strength for RFA, fresh and hardened mortar mixes, and evaluate the effects of RFA on the properties of mortar. The results indicated that the particle size distributions of concrete and mortar wastes were suitable for coarse grading, whereas those of bricks and ceramic tile wastes were for fine grading. The mortar mixes containing concrete waste showed dominant properties compared to other mixes. The properties of mixes with mortar and tile wastes were moderate, except tile waste had the initial setting time of fresh mixes extended. Brick waste was the most defective and suggested not to be used with high content.

Thuy Ninh Nguyen, Viet Hai Vo, Tuyet Giang Vo, Tuan Anh Le
Effect of Duration and Temperature of Initial Curing on Compressive Strength of Cement Paste Containing Fly Ash Activated by Sodium Sulfate

Fly ash (FA) is considered as a supplementary cementitious material that can help enhance long-term mechanical properties and durability of concrete. However, the compressive strength at early ages of FA concrete is low owing to slow pozzolanic reaction of FA. To overcome this problem, the present paper focuses on studying duration and temperature of initial curing for cement paste containing FA activated by sodium sulfate (Na2SO4) in order to promote the pozzolanic reaction. Three replacements of FA were 0, 20, and 40% by mass of binder while the Na2SO4 contents were 0 and 4% by mass of binder. After casting for 24 h, the cement pastes were cured at various temperatures (i.e., 27 ± 2, 40, and 80 °C) for 3 h and 6 h in a drying oven. The results showed the use of Na2SO4 as an activator increased compressive strength of the pastes regardless of the FA replacements and curing ages. Initial temperature curing reduced the compressive strength at the age of 28 days of the pastes with FA activated by Na2SO4. Long duration of high temperature curing negatively affected the compressive strength at the age of 28 days of the pastes. Consequently, long duration and high temperature of initial curing reduced the compressive strength at later ages of the cement pastes with FA activated by Na2SO4.

My Nhan Le, Thanh Hang Dang, Phuong Quyen Nguyen Dinh, Phuong Trinh Bui
Effect of Molarity of Potassium Hydroxide Solution on Heat Resistance of Fly Ash-Slag Based Geopolymer

Designing a building material with high fire resistance is crucial for minimizing the impact of catastrophic fire. Geopolymer, a new type of binder synthesized by the reaction of aluminosilicate sources with an alkaline solution, has been extensively studied as it offers comparable or even high durability when compared to ordinary Portland cement (OPC). The concentration of the alkaline solution is one of the important factors that affect the durability; however, there is very little data on the heat resistance of geopolymer activated with potassium hydroxide. Thus, this study aims to investigate the effect of molarity of potassium hydroxide on the heat resistance of fly ash-slag blended geopolymer paste. The potassium hydroxide (10, 12, and 14 M) and sodium silicate solutions were prepared as activator solutions. The initial heat curing at 70 ºC for 24 h was applied. In addition, an OPC specimen was also prepared for comparison. After curing for 28 days, some specimens were exposed to high temperatures (500, 750, and 950 ºC). The compressive strength of unexposed and exposed geopolymer and OPC paste specimens was measured. The results showed that the increase of molarity of potassium hydroxide solution increased the heat resistance of geopolymer in terms of retained compressive strength. Moreover, the geopolymer specimens could maintain higher compressive strength than that of OPC paste when exposed to high temperatures up to 950 ºC. This is attributed to the mineral composition of geopolymer, which is different from OPC paste, as studied by X-ray diffraction analysis.

Apriany Saludung, Takumu Azeyanagi, Yuko Ogawa, Kenji Kawai
Effect of Partial Replacement of Cement by Waste Sludge from Water Supply Plant on Compressive Strength and Water Absorption of Hardened Concrete

In this study, effect of partial replacement of cement by waste sludge from water supply plant on compressive strength and water absorption of hardened concrete was investigated to evaluate potential use of such waste for concrete production. After drying at 110 °C in a laboratory oven, the sludge was grounded and sieved to have a particle size of less than 0.14 mm to partially replace cement at levels of 0, 10, 20, and 30% by mass. Mixture proportion of reference concrete with 0% sludge replacement in which a desired slump and compressive strength at 28 days were 6 ± 2 cm and 45 MPa, respectively was designed according to Bolomey-Skramtaev method. All concretes with a water-to-binder ratio of 0.53 were prepared. The results showed that the waste sludge decreased slump of fresh concrete when the mixing water amount of all concrete mixture proportions was kept constant. The higher the waste sludge replacement, the lower the slump of fresh concrete. The partial replacement of cement by waste sludge in a range of 10–30% decreased the compressive strength of hardened concrete by 15.10–47.17% when compared with the reference concrete at the age of 28 days. The sludge replacements at 10 and 20% by mass increased the water absorption by 3.82 and 93.51%, respectively. Consequently, replacing 10% of cement with the sludge for concrete production was beneficial in terms of not only ensuring designed slump, compressive strength, and water absorption at the age of 28 days but also decreasing carbon dioxide emission from cement production and utilizing the waste sludge from the water supply plants towards sustainable development.

Ngoc Duy Vo, Ba Tien Mai, Ngoc Phi Long Duong, Phuong Trinh Bui, Xuan Loc Luu, Duc Thang Vu
Effect of Polypropylene Fiber Addition to Bottom Layer on the Mechanical Properties of Functionally Graded Concrete Containing Fly Ash

The present study focuses on effect of polypropylene (PP) fiber addition to bottom layer on the mechanical properties of functionally graded concrete (FGC) containing fly ash (Fa). The FGC specimens were prepared with two concrete layers having the same thickness. The top layer of FGC specimens was composed of normal concrete or Fa concrete without PP fiber, whereas the bottom layer was made from normal concrete, Fa concrete, or Fa concrete with 0.3% PP fiber. A constant water-to-cementitious materials ratio of 0.36 was applied for all mixtures. Fly ash was used to partially replace ordinary Portland cement by the proportion of 20% (by mass). The results showed that the flexural strength and impact resistance were significantly increased at the age of 28 days, whereas the compressive strength was slightly enhanced due to the PP fiber addition to the bottom concrete layer of FGC specimens. Functionally graded concrete using normal concrete in a top layer and Fa concrete reinforced with PP fiber in a bottom layer was an optimal material considering not only effectively economic aspect but also beneficial mechanical properties in terms of compressive strength, flexural strength, and impact resistance up to the age of 28 days.

Minh Luan Vo, Phuong Trinh Bui, Quoc Viet Dang
Effect of Pre-crack Length on the Moisture Distribution of Asphalt Concrete Pavement in a Short-Term Rain Event

This study was conducted to assess the moisture distribution in a pre-cracked asphalt concrete pavement in a short-term rain event by finite element method via the diffusion process. The asphalt concrete pavement with three different pre-crack lengths was used to investigate. The results show that the moisture distribution zone increases according to the time of the rain event and the pre-crack length of the asphalt concrete pavement. It is highlighted that the proposed model can effectively assess the moisture distribution in a pre-cracked asphalt concrete pavement. Moreover, this study also found that the pre-crack length affected the moisture distribution in the pre-cracked asphalt concrete pavement significantly. The pavement with higher pre-crack length had a higher increasing rate of moisture saturation with time. In the future, further research should be conducted to investigate the moisture distribution in a pre-crack asphalt concrete pavement in terms of different conditions such as material, environment, and traffic load.

Tan Hung Nguyen, Truong Phu Nguyen, Minh Triet Pham, Trong-Phuoc Huynh
Effect of Recycled Coarse Aggregate Treatment Using Cement – Sodium Bicarbonate Slurry on Compressive Strength of Hardened Concrete

Recycled concrete aggregate (RCA) from demolished constructions is a promising replacement to natural aggregate (NA) for concrete production. Nevertheless, the adhered old mortar on RCA particles is porous and weak, resulting in reducing mechanical properties of concretes. This study focused on using cement – sodium bicarbonate (NaHCO3) slurry to treat RCA in order to enhance compressive strength of concrete. RCA was disposed by soaking in the slurries consisting of 4% cement and 2, 4, 6, or 8% NaHCO3 for 48 h. Four RCA replacements were 0, 25, 50, and 75% by volume. All concrete specimens were cured in water before compression test at designated days (i.e., 3, 7, and 28 days). Untreated RCA concrete was prepared for comparative purposes. Outcomes indicate that the treatment by cement – NaHCO3 slurry significantly reduced water absorption and crushing value of treated RCA when compared with the untreated one. The compressive strength of concrete with untreated RCA was lower than that of concrete with NA. Compressive strength of concrete with treated RCA had intelligibly growth at all ages when compared with that of concrete with the untreated one. In general, this solution is an efficient method in improving RCA properties through the reductions of its water absorption and crushing value, resulting in an increase in compressive strength of concrete.

Quoc Hai Nguyen Phan, Hoang Tu Vo, Phuong Trinh Bui, Ngoc Thanh Nguyen
Estimation of Strength Development of Concrete Using Dielectric Measurements

This study found the possibility of estimating the strength development of concrete during the initial curing period using dielectric measurements. In concrete structures, the strength development due to hydration progress during the initial curing period is a critical process and determines the subsequent performance. The compressive strength of concrete is typically measured by compressing small cylindrical specimens that has been poured. However, since the strength development of concrete is greatly affected by such as surroundings and heat of hydration, the actual construction sites require a direct and non-destructive measurement method for the concrete structures. In this study, we conducted basic experiments to estimate the initial strength development by evaluating the hydration progress of mortar specimens using dielectric measurements. The results showed the dielectric measurements could evaluate the free and bound water state because there was the correlation between the time variation of dielectric relaxation time and the material age.

Ryota Isobe, Sachie Sato, Norihiko Kurihara, Seiichi Sudo
Service Life Prediction of Reinforced Concrete Coastal Structures in Vietnam Subjected to Chloride Ingress

Chloride-induced corrosion on reinforcing steel is one of the main causes that may shorten the service life of concrete structures. Recent studies have found that the deterioration process of these structures is highly influenced by material properties, environmental factors (exposure conditions) and climatic conditions (such as temperature, humidity, seasonal variations, etc.). For infrastructure in coastal areas of Vietnam, it has been observed that corrosion occurs within 10 to 30 years of service. The purpose of this paper is to carry out the service life prediction of reinforced concrete (RC) structures in coastal areas in Vietnam. A model simulation of chloride penetration into concrete before and after repair and under various climatic conditions is developed in FreeFEM++ software to assess the effects on structure service life. A case study is conducted in three coastal cities in Vietnam where the annual temperature and humidity vary. The results show that chloride ingress into concrete is highly influenced by weather conditions. In addition, some maintenance strategies, that are appropriate with the practical conditions in each area in Vietnam, are recommended to prolong the service life of corroding RC structures.

Quynh Chau Truong, Chinh Van Nguyen, Charbel-Pierre El Soueidy, Emilio Bastidas-Arteaga
Evaluation on Engineering Properties and Microstructure of Green Mortar Incorporating Steel Slag as Fine Aggregate

The use of industrial by-products as alternative materials to naturally sourced materials has been attracted researchers in the world. Following this trend, an experimental evaluation on the effect of using steel slag aggregate (SLA) to replace river sand (RS) on the engineering properties and microstructure of the mortar was performed. The SLA was used to replace RS at levels of 0–100% (an interval of 20%, by volume). The engineering properties of the mortars including compressive strength, water absorption, drying shrinkage, and ultrasonic pulse velocity (UPV) were tested up to the age of 56 days. The microstructure of all mortar samples was also observed. Test results showed that the replacement of <60% RS by SLA negatively affected the properties of the mortars. Increasing the replacement levels to 60–80% enhanced the performance of the mortars. However, the mortar sample with 100% SLA did not show any improvement in its properties. As expected, all of the mortar samples prepared for this study achieved the compressive strength values of all above the target strength of 10 MPa. In which, the 80% SLA sample obtained the highest compressive strength value of 17.4 MPa and 18.9 MPa at 28 and 56 days, respectively. This result was furtherly confirmed through the microstructure observation of the mortars. Consequently, SLA was found as a potential alternative to RS in the production of construction mortars.

Trong-Phuoc Huynh, Hoang-Phong Huynh, Tri-Khang Lam, Minh-Thien Do
Frost Damage Resistance of Portland Blast-Furnace Slag Cement Concrete Cured Internally by Using Roof-Tile Waste Aggregate

The purpose of this study was to clarify the relationship between the internal curing effect of roof-tile waste aggregate and frost damage resistance, and to investigate the effects of the replacement ratio of roof-tile waste aggregate as well as curing conditions on the frost damage resistance of concrete. Five types of concrete using Portland blast-furnace slag cement were prepared with a water-to-cement ratio of 0.50 and different replacement ratios of roof-tile waste coarse aggregate (20% and 50% by volume) and roof-tile waste fine aggregate (23% and 58% by volume). Concrete specimens were cured at 20 °C under sealed condition for 3, 7, or 28 days, and they were subsequently exposed to air at 20 °C and 60%R.H. until the age of 28 days. Then, the tests for resistance of concrete to freezing and thawing were carried out for 300 cycles in water, and the relative dynamic modulus of elasticity as well as the mass loss was assessed at the designated periods. As a result, it was found that sufficient frost damage resistance could be secured when the replacement ratio of roof-tile waste aggregate was approximately 20% by volume, and the improvement in frost damage resistance was observed especially when fine aggregate was replaced.

Taishi Kirimoto, Yuko Ogawa, Kenji Kawai
Influence of Superplasticizer on Workability and Early Strength of Fly Ash/Blast Furnace Slag Based Geopolymer Mortar

Recent studies have shown the presence of ground granulated blast-furnace slag (GGBS) in fly ash based geopolymer induced denser microstructures and better compressive strength. However, the inclusion of GGBS gives rapid setting time despite its benefit in terms of mechanical properties and could cause difficulty in handling the geopolymer in its application such as troubles with delivery time of fresh mix geopolymer concrete. This study aims to investigate the effect of polycarboxylate based superplasticizer, which is commonly used in Portland cement concrete to improve the workability and achieve appropriate compressive strength, on the fresh properties and early strength of geopolymer mortar. Geopolymer mortar was composed of fly ash and GGBS acting as binder with sodium silicate and 12 M of sodium hydroxide solution as alkaline activator. Alkaline to binder and fly ash/GGBS ratios were kept constant at 0.5 and 1.5, respectively. Superplasticizer was added into alkaline solution before casting at various dosages of 0%, 1%, 2%, 4%, and 8% by the binder mass and all the specimens were cured in two regimes of heat curing and 20ºC curing. The results have shown that the inclusion of superplasticizer maintained the workability over the time and may delay the setting of geopolymer mortar. Moreover, the mixture with 8% superplasticizer had dense microstructure and comparable compressive strength to that without superplasticizer at the age of 7 days.

Kemala Indriani, Apriany Saludung, Yuko Ogawa, Kenji Kawai
Mechanical Properties and Length Change of High Strength Concrete Containing Coal Bottom Ash as an Internal Curing Agent

Construction demand for high rise buildings is gradually increasing at several developing countries, leading to an over-exploitation of river sand which causes environmental impacts such as riverbank erosion. Coal bottom ash, which is a by-product of coal fired power plants, is considered as one of alternative materials to natural river sand for concrete production to diminish environmental impacts and conserve natural resources. Therefore, the aim of the present study was to investigate mechanical properties and length change of high strength concrete internally cured by coal bottom ash to evaluate the effectiveness of replacement of river sand by this material. In experiment, five replacements of natural river sand by coal bottom ash under saturated-surface dry condition were 0, 25, 50, 75, and 100% by volume. A water-to-cement ratio of 0.34 was employed for all concrete mixtures. Mechanical properties (including compressive strength and flexural strength), and length change (i.e., shrinkage) of high strength concretes cured under sealed condition were tested up to age of 56 days. Results showed that the replacement of natural river sand by coal bottom ash reduced compressive strength of the concretes at the age of 1 day. The 50% replacement of coal bottom ash increased compressive and flexural strengths of the concretes after aging for 7 days. The replacement reduced shrinkage of the high strength concretes up to the age of 56 days. Consequently, the coal bottom ash under saturated-surface dry condition is found to be a potential alternative to natural river sand to produce internally cured high strength concrete.

Phuong Trinh Bui, Trong Huu Nguyen, Van Chi Vo, Xuan Loc Luu
Microscopic Investigation on Interfacial Transition Zone in Fly Ash Cement Hydrates Using Roof-Tile Waste Aggregate

Previous studies reported that the strength reduction in fly ash concrete (FAC) can be improved by internal curing with roof-tile waste aggregate (RWA). However, how much the internal curing by RWA improved the compressive strength of FAC was different, and there was no clear explanation on it. The purpose of this study is to clarify the effect of the internal curing in the FAC by examining the range of the internal curing effect with RWA in the interfacial transition zone (ITZ) around coarse aggregate. Paste and concrete specimens in which part of cement was replaced with fly ash were prepared. For paste specimens, one aggregate particle was placed in the center of the specimen. Vickers hardness around the aggregate in the paste specimen and the compressive strength of the concrete specimen were investigated. As a result, the range of Vickers hardness improvement around RWA changed depending on the replacement ratio of fly ash. This indicates that the internal curing effect differs depending on the mixture proportion of paste matrix such as the replacement ratio of fly ash. Furthermore, it was observed that the compressive strength of concrete increased as the thickness of ITZ around RWA decreased.

Kazuma Okamoto, Phat Tan Huynh, Yuko Ogawa, Kenji Kawai
Physical and Mechanical Properties of Lightweight Fly Ash/GGBS Based Geopolymer Mortar Foamed with Hydrogen Peroxide

Vietnam is one of the countries in Southeast Asia that possesses many fly ash and ground granulated blast furnace slag. They are known as by-products from the thermal power plant and steel industries with rich aluminosilicate content to activate with alkaline liquid in geopolymer. In this research, hydrogen peroxide (H2O2) is used as a foaming agent in lightweight geopolymer mortar. The experimental work with mixed proportions of fly ash, ground granulated blast furnace slag, alkaline solution, fine aggregate, and foam agent is conducted to investigate lightweight geopolymer mortar properties. As a result, the flow diameter and flow time depends on the sodium solution to geopolymer solid ratio and fly ash to ground granulated blast furnace slag ratio. Besides, the higher percentage of foam agent and higher content of GGBS result in a more significant expansion degree of lightweight geopolymer mortar. On the other hand, the compressive strength of specimens decreases with the increase of foam agent and content of GGBS. In conclusion, the lightweight geopolymer mortar foamed with hydrogen peroxide shows a high potential to produce lightweight panels in construction.

Tuan Anh Le, Tan Khoa Nguyen, Thuy Ninh Nguyen
Study of the Properties of Concrete Using Mixed Recycled Coarse Aggregates of Different Qualities

In Japan, research on recycled aggregates has been conducted since the 1970s. The JIS standard compiles the findings from 2005 to 2007 and revised from 2018 to 2019. In these standards, the quality of recycled aggregate is divided into three levels: Classes H, M, and L. The applications of aggregates other than high-quality H are limited. However, Class-H aggregate has not been widely used because of the increased cost and energy required to produce better-quality recycled aggregate. One solution to this problem is to use a recycled aggregate of medium quality formed by mixing ordinary aggregate and recycled aggregate (mostly low-quality recycled aggregate) rather than using recycled aggregate alone in concrete. In this study, we investigate the strength and durability of concrete made from mixtures of recycled aggregates of different quality and normal aggregate. We confirm that the quality of concrete is higher when low-quality recycled aggregate mix ordinary aggregate than when alone use moderate-quality recycled aggregate.

Naoki Kawata, Sachie Sato, Hiroyuki Tanano
The Enhancement of Recycled Aggregate Concrete by Steel Fiber Reinforcement for Rigid Pavement

The use of demolition waste as recycled aggregate (RA) in concrete is a high demand for sustainable developments; however, there are drawbacks to replacing RA with natural aggregate. The purpose of this study is to evaluate the application of RA to rigid pavements with steel fibers (SF) as reinforcement due to its advantages in improving tensile strength and reducing cracks. Compression tests were conducted on concrete samples cast with several contents of SF and RA to determine their desirable contents. Flexible strength was determined using the four-point bending test to show the effects of SF on the drawbacks of recycled aggregate concrete (RAC). As a result, the concrete mixture was less workable when adding SF and/ or RA. Although the compressive strength and flexure strength of RAC were subsequently decreased when a part of natural aggregate was replaced by RA, some of them were recovered after increasing a small amount of SF. In summary, it would be a possibility of applying SF to RAC pavement for lessening damages and prolong its life span.

Thuy Ninh Nguyen, Tuan Anh Le, Hai Viet Vo
Utilization of Waste Incineration Bottom Ash as Fine Aggregate in the Production of Terrazzo Tiles for Pavement

Turning solid waste materials into useful construction materials has been attracted many researchers in the world. This study investigated the possibility of using waste incineration bottom ash (IBA) from local incineration plants in the production of terrazzo tiles for pavement. In which, the IBA was used as a crushed sand substitution at levels of 0–100 vol.% (interval of 25%). Test results show that all of the terrazzo tiles produced in this investigation exhibited consistent dimensions and nice shapes without visible defects. The incorporation of IBA reduced the flexural, whereas increased the surface water absorption and surface abrasion values of the tiles. However, all of the terrazzo tiles regardless of the IBA content met the requirements of TCVN 7744:2013 and were classified as Type-I, which is the highest quality of terrazzo tiles for external use. Moreover, scanning electron micrographs of the tiles well supported their engineering properties. Research results further demonstrated great potential in manufacturing terrazzo tiles using IBA as a fine aggregate.

Trong-Phuoc Huynh, Huy-Phuong Phan, Van-Hien Pham, Van-Anh Ngo, Hoang-Tung Luu

Geomatics Session

Create 3D Models from Photos Captured by Sony Alpha 7 Mark 2 Digital Camera

Creating a 3D model of the object is necessary for assessing the current status, exploitation, management, and information storage of the construction. Using photographs to create 3D models is a common practice. The photos of Solar BK construction are captured for generating the 3D point cloud using COLMAP open source application using structure from motion algorithm. However, the created cloud is not the right size and needs to be adjusted to the original size. In this study, the authors propose using the average scale to re-establish the construction's size. The average scale is calculated from the ten measured edges chosen horizontally and vertically around the building. The result obtains a dense point cloud model with nearly 2.7 million points. After correcting the point cloud, the lengths of the checked edges have an absolute error of no more than 3 cm from the actual size and a relative error of less than 1:80. The resulted point cloud is sent into AutoCAD software to reconstruct the 3D model of the construction manually. The results show the ability to create 3D models of objects from photos taken by digital cameras. This result is suitable for applications that do not require too high accuracy, such as building status management or building data visualization.

Anh Thu Thi Phan, Xuan Phuc Mai
Estimating PM2.5 Mass Concentration from MODIS AOD Products in Ho Chi Minh City, Vietnam

Air pollution, especially PM2.5 mass concentration is one of big problems in Ho Chi Minh City in recent years. This study focuses on deriving a linear regression model based on a relationship between ground-level PM2.5 mass concentration measurements and satellite aerosol optical depth (AOD) values. The PM2.5 measurements were collected from 25 ground stations in the inner city while atmospheric AOD values were extracted from Moderate Resolution Imaging Spectroradiometer (MODIS) green and blue band images. The observed period was from January 1, 2020 to May 31, 2020. As a result, the multivariable linear regression model was built from the sub-dataset of observations from the 20 ground stations. Correlation between PM2.5 mass concentration measurements and MODIS blue band and green band AOD values is relative high, that of 0.85, and RMSE of 6.439 (μg/m3). The remain subdataset of observations from the 5 ground stations were used to validate the model, and it indicated a correlation coefficient of 0.88 and a RMSE of 5.567 (μg/m3). The result model is expected to be applied for deploying air quality monitoring systems derived from satellite observations and understanding geospatial distribution of PM2.5 mass concentration in Ho Chi Minh City, Vietnam.

Phan Hong Danh Pham, Dang Khoa Le, Thi Minh Trang Nguyen, Vu Hien Phan
Extracting Ground Points and Generating Digital Elevation Model (DEM) from Point Clouds from Point Clouds

Digital elevation models (DEM) is essential information for leveling, surveying in building construction. There are many methods for generating DEM. Because of consuming much time and labor, directed methods are replaced by many indirect methods for generating DEM. In this study, DEM is proposed to be generated from point clouds rapidly collected by laser scanning or photogrammetry. Two datasets are used for checking the proposed data processing process. As a result, two ground point cloud areas were extracted. Many ground points in the steepest areas cannot be extracted. For a flat area with less than 10° of slope angle, the results of ground point extraction are good. The surface is divided into many equal grid cells for generating DEM, and the grid cell’s elevation is computed from the point’s elevation inside it. Finally, DEMs are displayed as TINs by creating Delaunay triangle networks.

Anh Thu Thi Phan, Quoc Thai Phan, Anh Khoa Viet Nguyen
Mangrove Classification Using an Integration of Radar and Optical Images of Sentinel 1 and 2: A Case Study of Can Gio, Ho Chi Minh City

Mangrove forests are of great importance to coastal communities, providing not only a source of food and resources but also protecting coastlines, preventing erosion and regulating our climate. However, mangroves have been changed significantly due to deforestation and restoration during the last decades. At present, remote sensing has been widely proven to be essential in monitoring and mapping mangrove forest. In this study, we exploited an integration of radar and optical images of Sentinel 1 and 2 to classify mangroves in the Can Gio district, Ho Chi Minh City. Sentinel-1 images were collected in February 2021 while Sentinel-2 images were in January 2021. Based on an analysis of training samples, a decision tree diagram was designed to classify the Can Gio mangroves with four major plants, consisting of nypa palm, rhizophoraceae, avicennia and ceriops tagal. The result presented a spatial distribution of the mangrove types inside the Can Gio mangrove forest and their sparse appearance in combination with other vegetation in the Can Gio district. The classifier for the Can Gio mangroves obtain an overall accuracy of 80% and Cohen’s Kappa coefficient of 0.75. The decision tree model on the integration of radar and optical images of Sentinel 1 and 2 was expected to contribute a large inventor of classification algorithms and to be effectively applied for mangrove classification.

Vu Hien Phan, Tan Nhat Le, Ngan Truong Nguyen

Geotechnical Engineering Session

Assessing Landslide Susceptibility in Korea Using a Deep Neural Network

Rainfall is a key triggering factor for landslides. Most of landslides in Korea were triggered by heavy rainfall. In this study, we used a deep neural network (DNN) to assess landslide spatial probability at Mt. Hwangnyeong, Busan, Korea. The results was validated based on 26 landslides using a receiver operating characteristic (ROC) curves. The areas under the curve (AUC) of the success-rate curve and predicted-rate curve showed that the proposed model was successful in predicting the spatial probability of landslide at Mt. Hwangnyeong. In addition, the DNN model was compared to the infinite slope model and showed better performance than the infinite slope model. The performance of the DNN model at three different activation functions were also compared to select the optimum function. This result showed that the DNN model with ReLu function has the best accuracy. A classified landslide susceptibility (CLS) map was established from the landslide spatial probability map by the geometrical interval method. A statistical test was performed and indicated that the classified landslide susceptibility map had statistical significance.

Ba-Quang-Vinh Nguyen, Thanh-Hai Do, Yun-Tae Kim
Investigation of Permeability of Dredging Sand Mixing Cement and Bentonite

The hydraulic conductivity of soilcrete specimens created from dredging sand mixing with cement and bentonite expects to be relatively low to apply as impermeable cores for embankments, dams, containment walls, and so on. Hydraulic conductivity of dredging sand samples taken in Dong Thap province mixed with a cement content of 300 kg/m3, various bentonite contents of 25, 50, 75, and 100 kg/m3, respectively, was conducted in the laboratory. The permeability tests followed the ASTM D5856 and D5084 standards for more than 3 months. The results indicate that: (1) The hydraulic conductivity of the dredging sand mixed with cement was lower 1000 times than that of the unmixed sand; (2) the hydraulic conductivity of the sand mixed with cement and bentonite was lower than that of the sand mixed with cement and slightly increases with increasing in bentonite contents; (3) the hydraulic conductivity of soilcrete decreases with increasing in curing times; (4) the hydraulic conductivity of soilcrete was identical with hydraulic gradients; (5) the hydraulic conductivity of soilcrete varied from 4.86 × 10–9 m/s to 1 × 10–10 m/s.

Bich Thi Luong, Phong Duy Nguyen, Hoang-Hung Tran-Nguyen, Khanh Duy Tuan Nguyen
Performance Analysis of Pile Under Negative Skin Friction by Load-Transfer Method

This paper presented a performance analysis of pile under negative skin friction by load-transfer method. In the analysis, the nonlinear t-z curves were applied to described the relationship between mobilized load and displacement at pile shaft and pile tip. A new iterative algorithm was proposed to determine the behavior of the pile. The analysis results were compared with the unified method. The results showed the proposed load-transfer method can be correctly performed the behavior of the piles more than the other.

Van Qui Lai, Suraparb Keawsawasvong, Thanh Hai Do, Quoc Thien Huynh, Quoc Viet Tran, Huu Thoi Tra
Solutions to Reduce Negative Effect of Saline Soil Cement Column in Ben Tre province

It is normally known that a negative effect on the strength characteristics of soil cement sample. This paper focuses on the effect of salt and bottom ash on the strength development of saline soil cement mixing in Ben Tre province. The saline soil cement samples (SSC) in this study consisted of saline soil, cement and bottom ash for recycling dredged soil in this area. Several pairs of samples with various bottom ash contents (i.e., 0, 50, and 100%) to have specimens of non-salt and salt-rich dredged soil with symbol as SSC-N and SSC-S, respectively. In this study, several series of unconfined compression test were carried out with curing time increase. It is found that bottom ash content decrease the negative effect in soil cement samples. In case of without bottom ash, at 7 and 28 days of curing time, the strength of SSC-N has approximately higher than that of SSC-S. It is found that the percent of strength reduction due to salt concentration is approximately 23% at 7 days and 11% at 28 days of curing time. It is worth to note that inclusion of bottom ash into soil admixture gives benefits of increasing shear strength due to pozzolanic reaction. This application is not environmentally sound, and societal demand to recycle waste material in sustainable development in Ben Tre province.

Thanh Hai Do, Van Qui Lai
Stability Factors of Cantilever Sheet Pile Walls in Clays by Using Finite Element Method

This paper presents a parametric study of the stability of cantilever sheet pile walls in clays by using the plane strain finite element analysis. In the finite element analysis, the cantilever sheet pile wall is modeled by using plate elements while the clay is modeled by using volume elements and obeys the Tresca failure criterion. The cantilever sheet pile wall has the excavated height and the embedded length. The clay has the unit weight and the undrained shear strength. By using the strength reduction method, the safety factor of the cantilever sheet pile wall at the limit state can be obtained. The results presented in the paper are illustrated in the form of design charts of dimensionless parameters, which are the relationships between the stability factor and the wall embedded length ratio. The proposed design charts of the stability factors can be employed to preliminarily estimate the embedment of the cantilever sheet pile walls that are widely constructed in practice.

Suraparb Keawsawasvong, Van Qui Lai, Quoc Thien Huynh, Chung Nguyen Van
Studying the Wave Propagation in the Soft Soil Medium Subjected to Low-Frequency Dynamic Effects

Dynamic effects on structures are complicated topics, both in theoretical and experimental aspects. This article aims to study more about the characteristics of the waves that originate from a low-frequency source of vibration, propagate through soil medium, and come to attack a receiver building in the vicinity. The virtual experimental method uses a finite element Plaxis 2D model in which the soil medium is compressible, subjected to a low-frequency vibration (i.e., pile driving and an impact loading in horizontal direction, both excitations have the same frequency f = 1.5 Hz). The mechanism of reflecting the waves from the source to the surrounding medium and the ground surface is studied by examining the direction of displacement vectors in different angles of propagation direction. The target focuses on determining the direction of propagation, reflects from the pile tip to the ground surface, and studying the additional settlement of the receiver footing due to the dynamic effects in the far-field. The former is to understand more about the decay of the body waves, and the mechanism of detaching the body waves to surface waves. Some preliminary results on free-domain displacement indicate that the longitudinal P-wave travels from the pile tip to along a line of which the angle is between 72 to 76° to the horizontal direction, and the transversal S-waves are detected at about 18 to 40° to the horizontal direction, and the surface R-wave may travel at a longer distance up to 50 m. The propagation velocity of R-wave in soft soil is calculated by dividing the distance by the time between two arbitrary points in the time-domain displacement, equals 35.5 m/s.

Tham Hong Duong, Thoi Huu Tra
The Correlation Between SPT and CPT Result in Sandy Soils in Ho Chi Minh City

This study establishes the correlation of test results in site from SPT and CPT in Ho Chi Minh City. Based on the soil investigation at the Phu Tho Hyppodrome, District 11, Ho Chi Minh City from the ground to 40 m depth, every 2 m/test SPT of 12 boreholes and 15 holes CPTu in the area of 10,000m2, the author collected, classified and evaluated geotechnical conditions and statistic to establish the correlation of test results in site from SPT and CPT. When the correlation function qc = 3748.1 × exp[(-0.126z2 + 7.006z – 47.711) × N30 × 10–3] is applied, the cost and time of geotechnical investigation will be greatly reduced, especially in CPT. This provides geotechnical engineers with the estimation of SPT based on the CPT results and vice versa, creates favorable conditions for the economic design in the state of equipment, economic limit or construction plan unfavorable.

Nhat Truyen Phu, Thanh Long Vo, Ba Vinh Le
Using Inverse Technique to Evaluate the Effect of Capillary Barrier on Hydraulic Properties of Unsaturated Multi-Layered Sand from 1-D Desaturation Test

A numerical study was used to estimate the applicability of the inverse analysis approach to assess the hydraulic properties of unsaturated soils under capillary barrier effect in a one – dimensional outflow experiment. A sample structure comprising a 400 mm thick layer of fine sand overlying a 400 mm thick layer of medium sand was set up in a Plexiglas cylindrical tube. The drying experiment was carried out to determine cumulative flux, soil resistivity and soil suction during experiment. Simultaneously, the unsaturated hydraulic properties were also calculated by a finite element program and an inversion program using measured value of soil suction and the outflow rate from desaturation test as input data. To evaluate the applicability of the inverse parameter estimation method, the comparison between computed and measured values of the unsaturated hydraulic properties of the layered sands was conducted. The results indicate that the inverse analysis based on the 1-D desaturation experiment can be used to evaluate the capillary barrier effect of unsaturated layered soils with reasonable accuracy…

Nam Viet To, Ky Viet Nguyen, Hai Hong Dao, Truyen Nhat Phu

Port and Coast Sessions

Assessing Wave Attenuation by Mangrove Forest in Bac Lieu Province Using XBeach

Mangroves naturally protect the coast against high waves, storm surges, sea level rise and erosion by dissipating the energy of the incoming waves. As the importance of mangrove forest is earning attention recently, it is necessary to assess the ability of mangroves in reducing waves. This paper analyzes the reduction of wave energy as well as wave height due to mangrove forests at the coast of Bac Lieu province based on the XBeach 1D numerical model. The factors that have most effect on the wave reduction efficiency of mangroves are forest density, forest band width, incident wave height and water depth. These results show that the minimum band width of mangrove forest should be equal to 500 m, 450 m, 250 m and 150 m with respect to the case of no mangrove, sparse, medium and high density in order to reduce approximately 95% of the energy of the incoming wave.

Nguyen Kiet, Nguyen Danh Thao
Mapping Tidal Harmonic Constant Map from Vung Tau – Bac Lieu, Viet Nam by Using a Numerical Model in Curvilinear Coordinate

Harmonic constituents are used to predict tide levels, each constituent represents a distinct factor contributing to the tidal regime. In this paper, a hydraulic model in the curvilinear coordinates is applied to simulate eight tidal constituents (M2, S2, O1, K1, N2, K2, P1 and Q1 from Vung Tau to Bac Lieu, Vietnam. The hydraulic model with the two-dimensional orthogonal curvilinear grid has the advantage of increasing the accuracy in the results at the domain boundary. The numerical method of this model derives from the solution of the Reynolds system of equations averaged over the depth in the curvilinear coordinate systems. The model verification is implemented based on the equilibrium of the tidal currents of energy. The results of this model are used to mapping tidal constituents from Vung Tau to Bac Lieu, Vietnam. From Vung Tau to Bac Lieu, the amplitude and phase values of the tidal constituents K1 are higher than those from Vung Tau to Tra Vinh and approximately as high as those in Bac Lieu with the amplitude of 0.5 m and a phase range from 3450 to 3500. Meanwhile, the amplitude values of the constituent O1 fluctuate within the value of 0.3 m–0.31 m, the phase values are in the range 2700−2850. The values of the constituent M2 is the highest (0.8 m–0.9 m) which is double that of the constituent S2.

Tran Thi Kim, Nguyen Thi Thu Hong, Nguyen Khac Thanh Long, Nguyen Ky Phung, Nguyen Thi Bay

Structure Session

A General Framework of Higher-Order Shear Deformation Theory for Free Vibration Analysis of Functionally Graded Microplates

This paper proposes a unified higher-order shear deformation microplate model for vibration analysis of functionally graded materials. The theory is developed from fundamental equations of the elasticity theory and modified couple stress theory, from which many different frameworks of size-dependent plate models are recovered. In order to capture the size effects, the modified couple stress theory with one independent length-scale parameter is used. The solution field is approximated by bi-directional series in which hybrid shape functions are proposed, then the stiffness and mass matrix are explicitly derived. Numerical results are presented for different configurations of material distribution, side-to-thickness ratio, size-scale-thickness ratio and boundary conditions on the natural frequencies of functionally graded microplates.

Van-Thien Tran, Trung-Kien Nguyen
An Experimental Study on Factors Affecting the Coefficients of Shrinkage, Creep, and Crack Occurrence During Basement Construction in High-Rise Buildings

This paper is an experimental study on factors affecting the coefficients of shrinkage, creep, and crack occurrence during basement construction in high-rise buildings. Recently, the construction phase is one of the most important steps in the development of a building. Therefore, this paper will analyze the causes, conditions, and effects of concrete cracks during the construction of basements in high-rise buildings by using testing in laboratories and on-site. Finally, some recommendations and suggestions for the control of basement cracks during construction will also be presented.

Phuc Binh An Nguyen, Quang Duy Tran, Quang Thai Bui, Quoc Viet Nguyen, Anh Tu Ta, Minh Quoc Le, Minh Duc Le, Van Hai Luong
An Improved Approach for Damage Identification in Plate-Like Structures Based on Modal Assurance Criterion and Modal Strain Energy Method

The modal strain energy (MSE) method is proven in many research pieces as an effective tool for damage detection in plate-like structures. However, in some complicated damage scenarios, the damage detection results are not accurate. This study presents an improved two-stage approach based on the Modal Assurance Criterion (MAC) and MSE method to boost the efficiency of MSE. Firstly, a new damage indicator named Modal Strain Energy Damage Index (MSEDI), based on MAC, is developed to locate potential damage elements more accurately in the first stage. Then, the damaged zones in plate structures are determined in both locations and extents in the second stage by minimizing an objective function using a genetic algorithm (GA) algorithm. Two different objective functions, global MSE, and local MSE are considered to examine their efficiencies on the performance of the GA algorithm. Finally, the feasibility of the proposed approach is investigated by numerical examples on a plate comprising multiple damage scenarios and different boundary conditions. The obtained results indicate that even in highly complex damage scenarios, the proposed improvement can identify the actual damage sites and estimate the extent of damage with high precision. The numerical results also show that the computational cost of the optimization process using the objective function based on local MSE change is much lower than that using the objective function based on global MSE change.

Thanh-Cao Le, Van-Sy Bach, Chi-Thien Nguyen, Manh-Hung Tran, Duc-Duy Ho
Bond Behavior Between Glass Fiber-Reinforced Polymer (GFRP) Bars and Saline Water–Sand Concrete

This paper presents an experimental study to investigate the bonding behaviour between GFRP bars and the concrete made from saline water and sand. The experimental program included twenty-four specimens of the concrete made from saline water and sand as an experimental group and six specimens of common concrete as a control group. The major survey parameters include the compressive strength of concrete (25 MPa and 35 MPa) and the diameter of GFRP reinforcing bar (12 mm and 16 mm). The specimens are examined under the pull-out testing method. The research results show that the average bonding strength of GFRP bars in the concrete made of salt-contaminated water and sand has only slightly been decreased from 5.6 to 7.2% compared to that in fresh water- sand concrete, and the decline degree of this bonding strength in 12 mm-diameter GFRP bars is more obvious than that in the 16 mm- diameter bars. The increase of concrete strength from 29.28 MPa to 35.56 MPa significantly enhances the average bonding strength of the 12 mm GFRP bar (18.7%), but only a slight improvement has been recorded in the 16 mm GFRP (6.3%). Increasing the GFRP bar diameter from 12 to 16 mm boosts the average bonding strength from 11.7 to 35.4%.

Hai La-Hong, Binh Thanh Nguyen, Dien Ngoc Vo-Le, Hue Ngoc Pham, Long Nguyen-Minh
Collapse Scenario of a Tested Steel Moment Frame on the Shaking Table

This paper provides a summary of column strength deterioration sequence during the collapse test of a steel moment frame on the shaking table. The study addresses the interaction of column axial force and bending moment capacity. Axial force developed in each column varies during the excitation. As a result, column bending moment capacity changes because of interaction with column axial force. On the other hand, local buckling occurring during pre-collapse time also weakens column strength. The deteriorated strength inherited after several pre-collapse load cycles determines the sequence of column failure when the building collapse happens. Global instability state is recognizable when the development of story drift contradicts to the decrease of building overturning moment. The building ends up with collapse after exceeding this state.

Tran Tuan Nam
Damage Identification for Steel Frame Structures Using Two-Step Approach Combining Modal Strain Energy Method and Genetic Algorithm

In this study, the location and extent of damage in steel frame structures are identified using a two-step technique that combines the modal strain energy (MSE) method and a genetic algorithm (GA). In the first step, the damaged elements in the frame are identified using Modal Strain Energy-based Index (MSEBI). This indicator is determined from the change of modal strain energy value of intact and damaged states. To improve the precision of the damage localization results, four first bending mode shapes are combined to calculate MSEBI. In the second step, the damage extents are determined accurately by GA with the objective function based on the MSE change. A numerical verification on a steel plane frame with four different damaged scenarios. The results show that the proposed approach gives a high accuracy in identifying the position and severity of damage for frame structures with different damage scenarios.

Van-Sy Bach, Thanh-Cao Le, Chi-Thien Nguyen, Manh-Hung Tran, Minh-Nhan Pham, Duc-Duy Ho
Designing Pre-engineering Steel Beam Using American and Vietnamese Standards

In this study, a steel beam of a Pre-Engineering Building (PEB) constructed in Binh Duong is analyzed and designed according to two American (AISC 360–10) and Vietnamese (TCVN 5575–2012) standards. The authors analyze and design beam structures of a PEB divided into two segments. Software SAP2000 is employed for analyzing the internal forces of the structure. Excel spreadsheet is established for designing steel beams using TCVN 5575–2012, while software SAP2000 is employed directly for designing steel beams using AISC 360–10. The weight of beams is estimated from the cross-section design results of two standards, then the cost of PEB beams is calculated based on their weight. The obtained results of beam design according to AISC 360–10 is more economical than TCVN 5575–2012 up to approximately 36% of the cost based on the mass of steel beams.

Van-Cua Bui, Phu-Cuong Nguyen
Dynamic Response of FGM Plate Under Thermal Load by Using Moving Element Method

The dynamic response of the functionally graded material (FGM) plate under moving load considering the effect of temperature is investigated. The FGM plate properties are graded in the thickness direction based on the power-law distribution in terms. The Mindlin plate theory is employed to calculate the shear strain of the plate. The properties of the FGM plate such as the elastic modulus and coefficient of expansion due to effect of temperature are modeled. It is assumed that temperature variation is only in the direction of the plate thickness and that temperature field is assumed to be constant in the plane. Temperature distribution function along the plate thickness can be obtained by solving the governing equation of temperature transfer. Both mechanical strain and temperature-induced strain are employed to calculate the plate strain. Comparison study with previous results were performed to verify the effectiveness of the proposed model. Effects of temperature, moving load, plate thickness, and foundation parameters on the FGM plate are examined. It is found that they have a significant effect on the displacement of the plate. As to be expected, the plate displacement depends on the temperature, volume fraction index as well as velocity, and magnitude of moving load, being larger when they are larger.

Minh Thi Tran, Quang Sy Tran, Van Hai Luong
Dynamic Responses of Composite Sandwich Plate Under Moving Load

This paper presents the dynamic analyses of composite sandwich plate resting on a Winkler viscoelastic foundation under moving load using the Multi-layer Moving Plate Method (MMPM). The governing motion equations of composite sandwich plate are established in a moving coordinate system joined to the moving load. The prominent advantage is that the load is static in this coordinate system, which prevents the updating of locations of load owing to the change of the contact points with the elements. To verify the accuracy of the MMPM, the dynamic responses of composite sandwich plate are examined. Next, the effects of load’s velocity on the dynamic responses of composite sandwich plates are studied.

Tan Ngoc Than Cao, Van Hai Luong
The Influence of Ambient Temperature on the Curvature of Displacement in Prestressed Concrete Girders

When external factors disrupt the test’s measurement signals, it is challenging to determine damage inside a structure. The purpose of this study is to provide preliminary suggestions about measurement noise when displacement curvature is used as an input for damage detection. Specifically, this study examined the effect of ambient temperature on the displacement curvature of a prestressed concrete (PC) girder during six months. The findings demonstrate that external temperature affects the vertical movement of the PC girders. Curvature estimations based on experimental data revealed a proportionate correlation between the curvature and the ambient temperature. The amplitude of the curvature grew as the ambient temperature rose. The calculated curvature changes between ‒0.0264 mm−1 and ‒0.0379 mm−1 when the temperature rises by one degree. Additionally, the regression analysis establishes that changes in ambient temperature may account for around 81–93 percent of the variation in displacement curvature. Thus, the ambient temperature was not the only factor influencing this change.

Tuan Minh Ha, Saiji Fukada, Phuoc Trong Nguyen, Duc-Duy Ho
Effect of Steel Fiber on Resistance of Ultra High Performance Fiber Reinforced Concrete Plates Under Impact Load

Ultra High Performance Concretes are significantly improving the bearing capacity of the structures under static as well as dynamic loads. An investigation on the behavior of Ultra High Performance Fiber Reinforced Concrete (UHPFRC) plates subjected to impact load was conducted in this study with three main factors of steel fiber, the strength of the concrete, and the amount of rebar. At the material level, a concrete grade of C120 and a steel fiber content of 1.0, 1.5, and 2.0% by volume respectively were used. All the samples have dimensions L500 mm x W500 mm x T80 mm, they are divided into two groups of with and without reinforcement. The experimental model is set up with a free-falling load acting at the center of the upper surface of the plate. Experimental results show that the steel fiber content directly affects the mechanical properties of UHPFRC such as compressive strength, flexural strength, fracture energy, and toughness of the material. The crack propagation corresponding to the impact loading is influenced by the amount of steel fiber in the concrete.

Thi Hai Vinh Chu, Duc Vinh Bui, Viet Tue Nguyen
Finite Element Simulation on Flexural Behavior of RC Slabs Using Coupled Damage-Plasticity Microplane Model

This paper focuses on applying and evaluating the available Coupled Damage-Plasticity Microplane (CDPM) model equipped with ANSYS software to represent the non-linear behavior of concrete material. The non-linear behavior of a reinforced concrete slab, subjected to a monotonically increasing load and designed according to the ACI 318-08 standard, is analyzed by the Finite Element Method. The three-dimensional finite element model of the three-point-bending test is established in ANSYS/Workbench. The three-dimensional eight-node hexahedral elements (CPT215) are used for simulating the non-linear behavior of the concrete member part, whereas the three-dimensional embedded elements (REINF264) are employed to model the reinforcement behavior of steel bars. The identification of parameters of the CDPM model for the reinforced concrete control slab is summarized and proposed based on an extensive literature survey. The results of the analysis of the load-deflection at the mid-span curve are presented and validated by the experimental results from the previous study to show the rationality and feasibility of the proposed finite element model.

Anh Khac Le Vo, Thai Binh Nguyen, Thi Nguyen Cao, Van Hai Luong
Golden Ratio Application in the Optimization of Cold-Formed Steel Sections

The golden ratio is a ratio used popularly and is a standard to evaluate the beauty in architecture. This ratio appears in the fundamental rule and satisfies sustainable conditions to form and structural geometries in nature. This study will approve a valuable characteristic of the golden ratio when applied for optimizing the cold-formed steel sections’ geometries. The optimized problem is established by combining the parametric design software, such as Rhino grasshopper and 3D Karamba, with an applied Octopus. The post-optimized geometric sections archive symmetric forms and high strength when a typical C section combines each other based on the golden ratio. Besides, the proposed sections are evaluated with the experimental results using a finite element analysis to increase the proposed approach’s reliability. This study performs reliable and robust parametric design tools, especially with every analysis step in the optimized process. We will create collected data to build a predicted model about geometries and the strength curves of structures using Machine Learning Tools in later research.

Tran-Trung Nguyen, Phu-Cuong Nguyen, Hoang Thao Phuong Nguyen
Integration of Sensors for Improved Damage Identification

Bridges are valuable assets to a society to overcome barriers of connection. The dependence on the bridge increases the demand for safety and reliability of the structure. However, the operational lifetime of bridges will be affected by the integration of bridge elements and their resistance to deterioration and damage. In this paper, the identification of damage in bridges using the influence line is presented. This approach is based identification and localizing of damage from a Modified Displacement-Based Index (MDBI) value. The effect of transverse position of the vehicle on the measurement of displacement sensor while crossing the bridge is addressed. Additionally, the road roughness effect has been considered to create a noise environment on the measured displacement response. The integration of strain sensor with displacement sensor to improve the damage identification have been addressed. The effect of noise has been greatly reduced by introducing strain based normalizing factor. Two case scenarios have been presented and the comparison of the previous DBI method and the MDBI method have been presented. In both cases, the MDBI successfully located the damage location against the odds in dynamic response effect and the noise.

Abdurehman M. Bali, Hiroshi Katsuchi, Hitoshi Yamada, Hiroshi Tamura
Investigation on the Performance of Non-uniformly, Discretely and Continuously CFRP Confined Square Reinforced Concrete Columns under Concentric and Eccentric loads

The behaviour of non-uniformly, discretely and continuously CFRP confined square reinforced concrete (RC) columns under concentric and 25 mm eccentric axial loads was investigated in this study. Eight square RC columns with a height of 800 mm and a side length of 150 mm were cast and tested. Two columns were reference RC specimens, two columns were non-uniformly confined with CFRP rings, two columns were discretely confined with three plies of CFRP rings and two columns were continuously confined with three plies of CFRP. The experimental results showed that non-uniform and continuous CFRP confinement significantly increased the load-carrying capacity and ductility of the square RC columns while discrete CFRP confinement resulted in a considerable enhancement of the load-carrying capacity and a significant improvement in the ductility. The improvement in the load-carrying capacity of the square RC columns due to non-uniform CFRP confinement was less than that due to continuous CFRP confinement but larger than that due to discrete CFRP confinement. However, the improvement in the ductility of the square RC specimens due to non-uniform CFRP confinement was larger than that due to discrete and continuous CFRP confinement under concentric axial load. It was also revealed that the brittle failure of CFRP confined square RC columns could be avoided by the application of non-uniform CFRP confinement.

A. D. Mai, M. N. Sheikh, M. N. S. Hadi
K-Fold Cross-Validation Technique for Predicting Ultimate Compressive Strength of Circular CFST Columns

Concrete-Filled Steel Tube (CFST) columns are a type of composite structure that has been widely used nowadays. It is known for its ability to withstand ultimate compressive strength and its efficient responsiveness in buildings with a modern appearance that transcends large spatial spans. Many design standards of many countries have also proposed calculation formulas, but design equations meet limitations due to experimental tests. If experimental data is large, specifically 663 specimens of CFST columns, determining the critical compressive strength for each sample is reliable and convenient in the case of Machine Learning prediction. In this study, prediction models of Supervised Learning approaches in Machine Learning such as Linear Regression, Logistic Regression, Linear Support Vector Regressor, Random Forest, Decision Tree, and KNN will be performed effectively in predicting the ultimate strength of CFST columns with only experimental raw data. The results obtained by this study show different influences in using the prediction models of the supervised learning approaches. Besides, to increase the stability of the prediction models, a cross-validation technique called K-fold is used with the data set divided into two parts, including 80% for training data and 20% for test data.

Tran-Trung Nguyen, Phu-Cuong Nguyen
Matrix Strength Effects on the Tensile Resistance of Strain Hardening Fiber-Reinforced Concrete with High Strength Steel Fibers

This paper aims to evaluate the influence of matrix strength on the tensile resistance of strain hardening fiber-reinforced concretes (SHFRCs) by performing direct tensile test. Two types of high strength steel fibers, twisted (T) and smooth (S) fibers, were reinforced at the volume content of 1.5% in different matrices, normal strength concrete (C1 with compressive strength of 28 MPa), high strength concrete (C2 with compressive strength of 84 MPa), and ultra-high strength concrete (C3 with compressive strength of 180 MPa). The test results indicated that T fibers in all matrices produced strain hardening behavior under direct tension whereas S fibers in C1 generated strain softening behavior. The tensile resistance of twisted fibers enhanced rapidly with the enhancement of matrix strength from 28 to 84 MPa, but increased slowly as the matrix strength enhanced from 84 to 180 MPa, while S fibers showed significant improvements in tensile resistance as the matrix strength enhanced. T fibers generated much better tensile resistance in C1 and C2 but slightly higher tensile resistance in C3 than S fibers. A SHFRC with post cracking strength of 11.5 MPa and strain capacity of 0.66% was obtained by using only 1.5% fiber volume content.

Ngoc Thanh Tran, Ngoc Minh Phuong To
Numerical Investigation and Comparative Study of Aerodynamic Characteristics in Rectangular, Corner Cut and Chamfered Sections by Using LES

In recent years, the length of bridges increases, and the main towers are becoming taller, thus it is necessary to improve the wind resistant performance of their main towers. Currently, corner-cut and chamfered cross-sections are used as static countermeasure of vibration in towers. However, there were some cases of vortex excitation due to the wind direction and cross-sectional shape when the main tower of a real cable-stayed bridge was examined. Therefore, it is required to examine the effective cross-section by understanding the flow and how corner-cut controls the separated flow. In this study, a comparative study of rectangular, corner-cut, and chamfered cross sections was conducted by using computational fluid dynamics analysis. It was confirmed that the drag coefficient and the variation components of lift coefficients were smaller in the corner-cut and chamfered cross sections than in the rectangular cross sections. It was also confirmed that the width of the separated flow was smaller in the corner-cut and chamfered cross section than in the rectangular cross section, and the pressure loss at the top surface and in the wake was also smaller. In addition, there was no significant difference in the aerodynamic characteristics between the corner cut and chamfered cross sections.

Daichi Tanimoto, Hiroshi Katsuchi
Post-buckling Analysis of Circular Functionally Graded Microplates Based on Isogeometric Analysis

This paper presents a novel numerical model for investigating the post-buckling response of circular Functionally Graded (FG) microplates. The size-dependent effect, which is observed experimentally for small-scale structures, is captured based on the Modified Strain Gradient Theory (MSGT). The Third-order Shear Deformation Theory (TSDT) proposed by Reddy is used to represent the kinematic relations of the plates and capture the shear deformation effect, while effective material properties varing in the thickness direction of the plates follow the mixture rule. The governing equations of the post-buckling problems are derived by using the principle of virtual work and then are discretized following the framework of Isogeometric analysis (IGA) by using Non-Uniform Rational B-Splines (NURBS) basis function to satisfy the C2-continuity requirement. Various numerical examples are conducted to verify the accuracy of the proposed numerical model and study the effects of size parameters and material distributions on the post-buckling responses of circular microplates.

Son Thai, Dieu T. T. Do, Vu Xuan Nguyen, Qui X. Lieu
Stochastic Vibration Responses of Laminated Composite Beams Based on a Quasi-3D Theory

Stochastic vibration responses of laminated composite beams based on a quasi-3D shear deformation theory are proposed in this paper. The mechanical properties of constituent materials are assumed to be uncertain, thus the free vibration responses can be modeled as random variables. A very large number of simulations is performed for propagating the overall uncertainty in the material properties to vibration behaviours by Monte Carlo simulation method. The higher-order shear deformation beam theory with nonlinear variations of both axial and transverse displacements is used and a trigonometric-series solution is developed to solve characteristic equations of motions. Novel numerical results are obtained to investigate the effects of uncertain material properties on the natural frequencies of the laminated composite beams.

Xuan-Bach Bui, Trung-Kien Nguyen, T. Truong-Phong Nguyen, Van-Trien Nguyen
The Extension of Multi-layer Moving Plate Method (MMPM) for Analysis of Functionally Graded (FG) Sandwich Plate

This paper presents an extension of Multi-layer Moving Plate Method (MMPM) for static and free vibration analyses of functionally graded (FG) sandwich plate resting on a viscoelastic foundation. The FG sandwich plate is composed of two parallel FG plates, in which upper plate is connected with lower plate by a viscoelastic layer and the lower plate rests on a viscoelastic foundation. The convergence and accuracy of this method are validated by comparing the results obtained from this study with other published results. Next, several numerical results are presented to examine the static and free vibration behaviors of FG sandwich plate with various volume fraction exponents, boundary conditions, geometric parameters, connected layer and foundation stiffness.

Tan Ngoc Than Cao, Van Hai Luong
The Relationship Between the Speeds of Moving Load and the Dynamic Responses of Doubled-Plates Floating on the Shallow Water in Mekong Delta by Using IMEM Method

In this study, the responses of doubled-plates floating on the shallow water in the Mekong Delta under moving loads are considered. Particularly, the structures are modelled by two thin plates which are connected through Winkler-type elastic layers. Meanwhile, the linear shallow-water wave theory is adopted to model the water. In addition, a recently novel numerical method, which is namely Integrated Moving Element Method (IMEM), is employed to solve the coupled system of numerical equations in this study because of the advantages of this method in comparison to the traditional Finite Element Method (FEM). According to gained numerical results, the effects of the ratio between the thickness of layers as well as the stiffness of core on the Dynamic Amplification Factor (DAF) of the floating double-plates will be investigated.

Ngoc Thuan Do, Xuan Vu Nguyen, Cong Huan Nguyen, Tran Nam Hai, Takayuki Suzuki, Van Hai Luong

Transportation and Infrastructure Sessions

Determinants of Risky Riding Behaviors Among High School Students in Ho Chi Minh City, Vietnam

This study examines the causal relationship between personality traits and latent factors in the Theory of Planned Behavior (TPB) in the Ho Chi Minh (HCM) City area. Four hundred nine students in grades 10, 11, and 12 have fully completed survey questionnaires to assess personality traits (anxiety, sensation seeking, anger, altruism, normlessness), latent factors (attitudes, subjective norms, perceived behavioral control, intentions), and risky riding behaviors. Research results show that sensation seeking directly impacts risky riding behaviors. In contrast, altruism has an indirect effect on these behaviors through attitudes and perceived behavioral control. The study also found that personality traits, latent factors, and risky riding behaviors did not differ between males and females. This study also revealed that personality traits play an important role in predicting risky riding behaviors in high school students, and the causal relationship can be explained through the TPB. In addition, a solution to improve students’ attitudes and knowledge about traffic safety will be proposed from the results of this study.

Thong Vo Manh, Long Nguyen Xuan, Minh Chu Cong
Effect of Dowel Bar Distance in Jointed Concrete Pavement Based on ABAQUS Program

Two dimensional finite element have been used for analysis concrete pavement for the past three decades to analyze rigid pavement response. In recent years with the development of a computer and an algorithm, the 3D finite element method (FEM) have been used as a powerful tool for a structure analysis, especially for the pavement analysis. This study concerns about the effect of dowel distance on the jointed concrete pavement such as the shear force along the dowel bar. The 3D FEM was established from Abaqus software. The 3D FEM was also verified in comparison with experiment data. The result of dowel distance could be used for further design in the jointed concrete pavement used in Vietnam.

Manh Tuan Nguyen, Ngoc Tuong Vy Phan
Field Assessment of Asphalt Concrete Incorporating Noise and Surface Friction

Pavement surface friction ensures pavement skid resistance when the vehicle tire contacts to the pavement surface, helping the vehicle to circulate safely. Friction evaluation has become an important tool in the evaluation of pavement surface quality. Macro-texture and micro-texture are two basic components when analyzing pavement surface friction. To assess friction in many asphalt concrete surface, the study used a British pendulum and sand patch test is conducted. In addition, the British pendulum will simulate the process of interaction between the vehicle tire and the pavement surface for measuring noise. Noise generated from testing will be measured by specialized equipment. The paper evaluates the pavement surface friction from the field experiments. The paper also shows the relationship between noise and surface friction.

Ngoc Tram Hoang, Manh Tuan Nguyen
Hamburg Wheel Tracking Assessment of Hot Mix Asphalt Using RFCC

The paper presents research results on the Hamburg wheel tracking test (HWTT) of asphalt concrete using RFCC. RFCC (Residue Fluid Catalytic Cracking) is waste from the oil refinery. RFCC is used as filler powder in the hot mix asphalt. Tests for rutting resistance were performed following AASHTO T312:2004 and EN12697-33. Dense graded asphaltic concrete of the nominal maximum aggregate sizes of 12.5 mm with and without RFCC as filler powder was tested using HWTT. The rutting resistance properties of asphalt concrete using RFCC are compared with conventional asphalt concrete using limestone powder. Experimental results show that RFCC can help asphalt concrete improve its resistance to rutting.

Anh-Thang Le
Laboratory Assessment of Recycled Polyethylene into Hot Mix Asphalt in Ho Chi Minh City

In Ho Chi Minh city, the flexible pavement system is getting more and more damages come from variety of reasons such as heavy traffic loading and limitation of maintenance procedure. Many methods were introduced and one of the most effective solutions is polymer modified asphalt concrete instead of conventional asphalt concrete as well as polymer modified asphalt concrete is relatively expensive. As a result, recycled polyethylene from waste plastic bag into hot mix asphalt concrete mixtures to create polymer modified asphalt concrete with a reasonable cost is a solution. Recycled polyethylene used in this study is granular form which size is from 1 to 3 mm. The contents of polyethylene replaced asphalt binder are 6, 9, 12, 15, 18% by weight of asphalt binder. The paper shows the mix design of asphalt concrete with recycled polyethylene and evaluated tests including Marshall stability, indirect tensile strength, Cantabro durability and resilient modulus. The 12% could be the best content of PE.

Ba Tu Vu, Manh Tuan Nguyen

Water Resources Session

A Comparison Study of Water Pipe Failure Prediction Models

Water leakages have been a major problem for water supply companies, one of the main causes of this problem is pipe failure in the water supply network. The risk prediction models of the pipe failure are also constantly being improved to determine the location of these leaks accurately and quickly. The statistical model is the Logistic Regression model (LR) used for failure prediction in groups of pipes. Machine Learning approaches, particularly the Decision Tree model (DT) and the Artificial Neural Network model (ANN) are compared in predicting individual pipe failure. In this paper, we proposed applying these three models to predict pipe failure for the DMA17 water supply network in ward 17, Go Vap District, Ho Minh city. Using Area Under the Curve (AUC) value to evaluate the modeling results, comparing this value showed that the ANN was the most suitable for water pipe failure prediction.

Thi Minh Lanh Pham, Quang Truong Nguyen
A Method for Calculating Unsteady Seepage at Riverbank

The paper presents a method to calculate the unstable seepage at riverbank. The Laplace’s equation in saturated zone is solved by the finite element method. Time derivative terms are discretized using implicit finite difference schema. The method considers three special factors of seepage including the change in time of water level of river; the variation in time of the phreatic line; and the variation of discharge face on river slopes. In response to the changes in time of the phreatic line, the computation mesh is modified at each step. The computation grid modification is performed using transformation. Although the implicit finite difference schema is used for discretization of time derivative terms, it is not required to know old pressure head at the nodes in new location. The method has been verified through a number of problems performed by other authors, including steady and unsteady seepage through rectangular earth dams, seepage flows through dams with a periodic boundary condition. The calculation results show that the method has a good accuracy.

Giang Nguyen Mong, Hong Tran Thi My, Hoa Nguyen Thi Thanh, Giang Le Song
An Approach of Seepage Analysis Through Earth Dams Considering the Uncertainties of Soil Hydraulic Conductivity

This study focuses on an approach for analyzing seepage mechanism through earth dams whose soil hydraulic conductivities are considered as random variables. The approach employs finite element analysis integrated into a popular software for seepage consideration and an easy-to-implement algorithm for the random field generation. Hence, a Monte Carlo method is used for the further analysis. Based on the analysis of the outcomes, there are three aspects that need to be warned when using this method. Firstly, the correct algorithm of the random number generation leads the relevant observed frequency distributions to normal-distribution shapes. Secondly, the refinement of mesh can lead to more accurate results in terms of numerical issues but that can change the scale of fluctuation of random field. Finally, a number of 500 samples for a Monte Carlo simulation is acceptable.

Thi Tuyet Giang Vo, Vo Trong Nguyen
Estimation of Sustainable Aquifer Yields in the Saigon River Basin

Since the 1990s, under the pressure of socio-economic growth in Ho Chi Minh City and nearby provinces, groundwater becomes an essential resource for domestic and industrial purposes. At the same time, the surface water supply utilities still struggle to satisfy the total water demand in the developing region. The conjunctive use of surface and groundwater is an essential strategy of water supply management that has to be considered coupling with aquifer yield and surface water capability within a basin. The study aims to determine optimal intensity pumping and estimate aquifers yield within sustainable drawdown criteria. The optimal pumping intensity was analyzed from maximum existing pumping per square kilometer in four aquifers with no negative impacts on Saigon River Basin’s groundwater system. The study estimated the sustainable aquifers yield through increasing pumpage until the lowest drawdown of aquifers meets the drawdown criteria. Here, the drawdown criteria considered the groundwater pumping laws of Vietnam and the hydraulic gradient at the salinity interface. Regarding drawdown criteria and hydraulic gradient at salinity interface criteria, the drawdown constraints are –20 m. MSL for aquifer 2 and ‒30 m. MSL for aquifer 3 and aquifer 4. The simulation inputs utilized the historical 20-year climate data. According to the pumping scheme in the existing area, the optimal intensity pumping for aquifer 2, aquifer 3, and aquifer four are found to be 2000 m3/day/km2, 3500 m3/day/km2, and 4000 m3/day/km2, respectively. Based on the optimal pumping intensity, the sustainable aquifers yield in Saigon River Basin are estimated to be at the rate of 1.9 MCM/day, which includes 57,699 m3/day from aquifer 1, 465,233 m3/day from aquifer 2, 455,151 m3/day from aquifer 3, and 925,836 m3/day from aquifer 4.

Tran Thanh Long, Sucharit Koontanakulvong, Phu Nhat Truyen
Microplastic Removal Time in Saigon River

Microplastics have been a serious problem for the aquatic life because they can convey toxic additives to the food web networks where human is at the highest level. However, the harm is supposed to be less if microplastics are out of the water body, which can be defined as floating at the water surface or burying at the water bottom. In this paper, we processed the microscope images of microplastics collected in Sai Gon River reported in a previous sampling campaign using MATLAB image processing application, and predicted removal time of different microplastic types using an appropriate velocity formula. We found that the removal time of fiber MPs in Saigon River can range between 12 to 130 h and that of flat fragment MPs is about 2 to 35 h. The removal time of one-dimensional MPs is mostly controlled by their diameter while two-dimensional MPs are affected by all of the geometrical factors. One-dimensional MPs in Saigon River tend to stay longer in the water column body, therefore, may have more negative impacts on the aquatic health than two-dimensional MPs.

Tuan Dang Pham, Minh Huy Nguyen, Thu Ha Nguyen
On the Flood Reduction Effect of Reservoirs in the Vu Gia—Thu Bon Basin in October 2020 Flood

In October of 2020 on the Vu Gia—Thu Bon river basin, there were two large floods. Due to resulting heavy losses, there have been doubts about the effects of upstream reservoirs in flood prevention and control. The aim of this study was to re-evaluate the role of those reservoirs. The numerical modeling method was used for this analysis. An integrated 1D/2D model was developed using the flow in the rivers was as 1D and the flow on the floodplains as 2D. There are two computational scenarios to be considered. In scenario considering the presence of the reservoirs, the discharge imposed at the upper model boundary is the actual one. This discharge is the result of operation of the reservoirs. In the scenario considering no reservoirs, the discharge imposed at the model upper boundary is calculated from the actual discharge to the reservoirs, with the regulation of the reservoirs neglected. The simulation results of these two flood scenarios clearly show that the reservoirs have significantly reduced floods downstream.

Hoa Nguyen Thi Thanh, Hong Tran Thi My, Thao Nguyen Thi Thach, Giang Le Song
Uncertainty-Based Seepage Analysis Through Different Types of Earth Dams

This study presents the seepage analysis through three popular types of earth-fill dams whose hydraulic conductivities are considered as spatially random. This study focuses on evaluating two important parameters of seepage which are the flow rate and gradient. These outcomes then are compared with ones resulted from the deterministic calculations. Hence, within all three types of dams, there is a probability of 100% in which the flow rates calculated from the random method are greater than ones from the deterministic method. As a meanwhile, there is a probability of about 50% in which the gradients calculated from the random method are greater than ones from the deterministic method.

Thi Tuyet Giang Vo, Vo Trong Nguyen
herausgegeben von
J. N. Reddy
Chien Ming Wang
Van Hai Luong
Anh Tuan Le
Springer Nature Singapore
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