Advances and Challenges in Structural Engineering

Many existing worldwide Reinforced Concrete (RC) structures, such as non-ductile RC frames, were designed for gravity loads only during the 1950s through 1970s or earlier. Due to variations in the identification of seismic active zones by national codes, such structures may not satisfy the current design requirements, especially when lying in a recently identified seismic active zone. This is because such structures, as a result of poorer reinforcement detailing, may generally do not possess the adequate ductility and strength needed to withstand an expected earthquake. Consequently, older RC frames may undergo substantial damage during earthquakes. One of the main damage aspects in such case is clear cracks around and within the beam-column connections. This is the case where the failure of beam-column joints is governed by bond and shear failure mechanisms which are usually brittle. This may be attributed to inadequate shear reinforcement in the beam-column joints region., This paper presents the first results of an experimental campaign performed – at the Laboratory of Materials & Structures of the Arab Academy And Technology (EGYPT) – with the aim to investigate the seismic performance of RC beam-columns joints strengthened with FRP. The experimental program includes testing specimens realized to be representative of existing exterior beam-column subassemblies with inadequate seismic details. A technical solution was selected in order to improve the joint seismic behaviour, and the performance of the proposed strengthening system is investigated in this paper. To this aim, two as built beam-column joints have been tested, one strengthened specimen and a reference unstrengthened one. Test results provide useful information for the adopted strengthening systems in terms of strength, ductility and energy dissipation capacity. Results indicate that the proposed strengthening technique was successful in adding up to 50% of the beam column joint capacity. The results are encaging to apply this technique on existing gravity load designed buildings.

The most modern railway systems have fully adopted clean energy for train and track operations. Trains or rolling stocks are powered by electricity through the overhead wire or the third rail on ground. Commonly, the overhead line equipment (OHLE), which supplies electric power to the trains, is widely adopted in new railway networks around the world since its system enables trains to operate smoothly while track inspectors can safely work on tracks. The OHLE is supported by mast structure, which is located at the lineside along the track. The mast structure is often made of steel structure built on mat or pile foundation. Due to the train passages, ground-bourne periodic forces may cause damage to the OHLE structure especially mast structure, connections and its foundation, which can lead to operational failure of train electrification. On this ground, the structural integrity of mast structures must be inspected regularly. In this study, the modal analysis is used in order to identify the mode shapes and natural frequencies of the mast structure. A mast structure with varying rotational soil stiffness is used to construct dynamic influential lines for soil-structure integrity prediction. Finite element model updating technique has been used to perform modal analysis and modal parameter identification. This paper presents the integrated numerical of three-dimensional mast structure considering soil-structure interaction to evaluate the condition of OHLE structures for maintenance planning. The outcome of this study will help civil and track engineers to effectively and efficiently inspect OHLE structures using ground borne vibrations from train passages.

Concrete bridges are very popular in Vietnam. However, under severe environments of the tropical climate, they can be lead to defects or deterioration with excessive rate. This point demands on materials performance with respect to extremes in not only stress and strain but also the properties of cementitious materials in practical design. In addition, cracking, shrinkage and creep of concrete due to the rapid ambient conditions of temperature and humidity are also a major challenge to researchers in Vietnam. Therefore, improving the sustainability of bridges by applying high performance concrete is very necessary. Recent developments in nanotechnology have given a lot of new challenges to produce the eco-friendly high performance concrete. It has been found out that use of nanotechnology through using nano-silica as a mineral admixture to modify the properties of the cementitious materials has significantly improved the performance of concrete. This paper investigates the effect of nano-silica as an addition on new concrete generation, the advancements in nanotechnology on the properties and performance of cementitious materials; and the application to concrete bridges in Vietnam in near future for sustainable development purpose.

Infrastructure safety, durability, and serviceability have been significantly enhanced as a result of improved construction materials over the past two decades. Concrete-filled fibre-reinforced polymer (FRP) tubes (CFFTs) system is one of the most promising technique to protect the reinforced concrete structures from aggressive environmental conditions. Most of the experimental investigations performed on CFFT columns have focused on short, unreinforced, small-scale concrete cylinders, tested under monotonic axial loading. In contrast, only few studies have so far investigated the effects of the internal longitudinal reinforcement type (steel or FRP bars) on the behavior of CFFT long columns. This paper presents preliminary test results of an experimental study on the behavior of concrete-filled FRP tube (CFFT) columns internally reinforced with steel and FRP bars. Six reinforced concrete (RC) and CFFT columns were constructed and tested until failure. The test parameters were: (1) internal reinforcement type (steel, glass FRP (GFRP), and amount, and (2) GFRP tube thicknesses. All columns had 1900-mm in height and 213-mm in diameter. Examination of the test results has led to a number of significant conclusions in regards to the trend and ultimate condition of the axial stress-strain behavior and mode of failure of tested CFFT columns. These results are presented, and a discussion is provided on the influence of the main test parameters in the observed behaviors.

The concept of concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs) is promising for a variety of structural applications and a good alternative for innovative constructions because of numerous attractive features, including durability and concrete confinement. An extensive research work was conducted on circular (CFFT) with and without internal bars for beams and columns. However, much less attention has been given to rectangular CFFT especially those reinforced with internal reinforcement bars. This paper aims at developing a simplified analytical design method to predicate the ultimate moment capacities of previously tested steel-reinforced rectangular CFFT beams at the University of Sherbrooke. A wide range of test parameters was considered such as the FRP tubes thickness, fibre laminates, and steel reinforcement. The proposed design method was found to be acceptable for predicting the ultimate moment capacities of the beams. The accuracy of the theoretical analysis showed good agreement with the measured values.

Before and after the 1980s, the China built many reinforced concrete multi-rib arch bridges. With the increase of traffic volume and load, the carrying capacity of the multi-rib arch bridges are obviously lower, it is necessary to take various measures to strengthen and enhance bearing capacity of these bridges. This paper proposes a reinforcement method by adding cable towers in two ends abutment of arch bridges and the inclined cables to improve behavior of RC multi-rib arch bridge. The main idea is that additional bridge towers are set on two side abutments of the RC rib arch bridge with single span to hang stayed cables. Newly-casting RC longitudinal beams are set in two sides of the bridge and the transverse prestressed steel tendons with $$ 4{\upvarphi }^{\text{j}} 15.24 $$ steel strands on the both sides of every cross beam were stretched, which are wrapped by the steel tubes and connected with longitudinal beams, to enhance the integrality and stiffness of the multi-rib arch bridge. Then, the longitudinal beams of each side of arch bridge are supported by using stayed cables through the cable tower. Comparison of the values gained by space finite element and field test confirmed that the proposed method for strengthening the rib arch bridge and enhancing the bearing capacity is effective.

The earthquakes are abrupt and sudden, and, in few seconds, they can lead to huge casualties. Nowadays, several approaches can be used to better know the seismic movement than we can expect when and where will have an earthquake. These approaches kind, always begins with a full study of the seismic action: the seismic birth, the wave formation and propagation, accelerometers and associated spectrum representation, etc.The aim of this study, on the one hand, is to construct and examine the spectral response of the ground motion for many earthquakes, on the other hand, is to study their influence on the structures height.We studied the acceleration files for the loma prieta (6,9 Mw) and the landers earthquakes (7,3 Mw) which had an important magnitude and caused significant damage to human life and property.

Due to limited modes of practice of utilization, huge amount of iron and steel slag dumped in yards of each production unit and engaging of important agricultural land and gave pollution to whole environment. The effective use of steel slag, as by product of steel industry which is sustainable construction material, in cold bituminous emulsion mix (CBEM) has ultimate benefits such waste disposal, saving natural resources and lowering cost of roadways. Effect of mixes prepared with steel slag were compared with the mixes prepared with replacement of cement and control mix. Experimental work was carried out on the sample of control mix, mix with cement replacement and modified mix. For modified mix, steel slag were replaced by 10%, 20%, 30% and 40% of aggregate having same size as of steel slag in gradation. Filler were replaced by 1%, 2% and 3% of weight of total aggregate by cement. Optimum emulsion content of each mix obtained by using Marshall stability test and comparison of stability values were carried out. The comparison of results of indirect tensile strength test and retained stability test on CBEM prepared with steel slag, cement and control mix. Significant improvement in Marshall stability, retained stability and indirect tensile strength of mixes prepared with the replacement of steel slag as compared to control mix and mixes prepared with replacement of cement.

Finding viable markets for post-consumer cullet generated in North America has been very challenging due to the predominant collection practice of glass commingled with other recyclables such as paper, ceramics, food particles, and glass of fluctuating colors and compositions. Thus, more than 60% cullet still ends up in the landfill. In this paper, potential end markets that could utilize this type of cullet with minimal level of processing have been identified. Based on several field trials conducted as well as the evaluation of the engineering properties, environmental impact, and safety issues, mixed cullet aggregates could be successfully blended with natural aggregates at different proportions for road-based applications, asphalt pavement, and concrete, utility and other construction projects. The debris level of the cullet aggregates for most of the applications should be maintained at 5%. Despite the vast potential end markets being identified, market demands still remain low. One of the major obstacles is the relatively high processing cost for cullet in comparison to competing natural aggregates. Therefore, to enhance recovery and develop strong market demands for cullet, there is a need for government interventions through the provision of recycling incentives, landfill ban, raising of tipping fees, and enforcing laws on the use of cullet as a construction aggregate.

Cement production is one of the most important industry and produce a lot quantity of by-product (waste) materials which called cement kiln dust, CKD. In Iraq about 1600 tons of CKD produced each day. Bricks can be produced using different methods, most of them uses the clay as row material and consists of firing process. Another method consists of using waste materials such as Fly Ash, FA. Most of researches focused on the use of CKD in road pavement applications and soil stabilization, etc., but rare researches used the CKD to produce bricks. Two types of CKD, two types of sand and one type of cement have been used in this study. The experimental work consists of three stages. In stage I, one type of CKD and one type of sand has been chosen to complete the stage II due to enhancement in mechanical properties (compressive strength, CS and absorption, Ab) of the produced brick. In stage II, the selected CKD and sand have been mixed with water and cement and pressed to form a molds using a pressure of 6 Mpa. The stage III aimed to enhance the compressive strength, CS and absorption of the produced brick by increasing compressive strength to 11 Mpa without increasing cement percentage to decrease the production cost. All of the properties of the bricks that were tested found to be satisfactory according to the ASTM C62-04(SW, MW and NW) and Iraqi Specification Standard ISS 25/1988, for type A, B, and C. The results of this study has the nobility of producing new type of brick using waste materials with low cost and without adverse effect on the environment and agriculture.

Background: Many historical and archaeological masonry structures located in seismically moderate and active areas are not capable of sustaining seismic and dynamic actions. Furthermore, recent earthquakes in urban areas like Cairo, Egypt have clearly demonstrated an urgency to upgrade and strengthen these deficient historic masonry structures. Retrofitting with CFRP is now extensively being used as a seismic retrofitting method all over the world. It increases the load bearing capacity of structural elements like beams, slabs, walls and columns; Improve the seismic ductility of masonry stone and brick columns and piers; Improve the seismic response of concrete beam-column connections, shear walls and collector elements; Improve the seismic performance of masonry shear walls and in-fill walls; Restore structural capacity to damaged or deteriorated historic and modern concrete structures.Objective: The aim of the present research is to investigate the application and durability of historical circular masonry stone columns completely strengthened by carbon fiber reinforced polymer (CFRP) laminates. This paper presents a comprehensive review with complete project experimental and implementation of CFRP in strengthening and seismic retrofitting of eight internal circular masonry stone supporting columns in the Saint George church in old Cairo area in Egypt and other important monuments in Cairo.Results and Conclusion: Strengthening and seismic retrofit with CFRP materials has gained notable acceptance from the archaeological structural restoration communities in recent years. CFRP is characterized with high strength to weight ratio, excellent resistance to creep and fatigue, extremely durable and low aesthetic impact. Its benefits include the add strength without adding dead load, Withstands sustained and cyclic load conditions, extremely resistant to wide range of environmental conditions, and easy to conceal.

Self-compacting concrete (SCC) is a highly flowable, non-segregating concrete that has the ability to flow in every spot of the complex formwork and consolidate within that without any external compaction. Steel fiber reinforced self-compacting concrete (SFR-SCC) is a new mixed material that merge the advantages of the SCC with those of steel fibers in improving concrete mechanical properties. This paper is part of a study to analyse the effect of steel fibers on the rheological [J-ring test] and mechanical properties [compressive strength and four point bending test] of SCC. Five concrete mixtures were evaluated. The primary experimental variables are the type and aspect ratio of steel fibers. Test results have shown that the inclusion of fibers improves the compressive strength of SCC but it has a negative effect on the rheological properties of the SCC by reducing the slump flow and increasing the flow time, but better workability was obtained as aspect ratio of the steel fibers decreased. It was also found that the fiber geometry is a key factor affecting the mechanical performance in particular the toughness of the SFR-SCC material.

A fibre-reinforced polymer (FRP) cycle footbridge has been proposed for construction in Bristol, United Kingdom for South Gloucestershire Council. The superstructure will span 54 m, comprising a bowstring carbon fibre-reinforced polymer (CFRP) arch with a 5 m wide glass fibre-reinforced polymer (GFRP) deck supported by stainless steel hangers. Recently, a methodology has been proposed that provides a structured process to assess the value of a structural health monitoring (SHM) system for a bridge prior to deployment. This methodology outputs a simple metric that quantifies the likeliness of an SHM system to yield value to an asset owner. This FRP bridge is used as a case-study to ‘road test’ this process. Two possible systems were considered: a system of accelerometers and a system of strain gauges. From the resulting discussions, a deployment of accelerometers received a value-rating (VR) of 4.2. A strain gauge deployment received 3.7. The scores will contribute to a monitoring specification for the FRP bridge which is currently in the design phase. Expansions to the methodology have also been proposed to better capture the potential value of an SHM system which would be of interest to structural engineers and researchers, in particular to inform model validation and research activities.

In recent years, a new interest has in fact arisen in the displacement based seismic design, especially in tall buildings. Several contributions have already been submitted for the development of different procedures based on displacements with the aim to simplify the evaluation of seismic demands of structures. In this paper, an improved procedure based on displacements applicable to the analysis and design of tall buildings is presented and illustrated by examples. It is considered as a new procedure for estimating the seismic deformation of Multi-Degree-of-Freedom systems. An example of a calculation that highlights the steps involved in applying this inelastic response evaluation approach is included to demonstrate the simplicity of the method. The accuracy of the proposed procedure is verified against the Nonlinear Time History Analysis (NL-THA) results and Uncoupled Modal Response History Analysis (UMRHA) of a 9-story steel building subjected to El-Centro 1940 (N/S) as a first application. In the second application the accuracy of the improved procedure is verified against the nonlinear time history analysis results of two tall buildings. The comparisons showed that the new method gives accurate deformations.

In this study, the differences in the pore structures densified by the blast furnace slag (BFS) sand and powder were investigated by using the mercury intrusion test and removing the fine particles contained in the sand. By using BFS sand, the pores with a diameter of 400 nm or higher were densified. The characteristics of the transition zone detected in natural sand were not observed with the elemental analysis around the BFS sand. A strong correlation was found between the volume of the pores densified by mercury intrusion method and drying shrinkage and the air permeability coefficient. It was verified that the densification and adhesion strengthening of cement paste and sand by BFS sand improve the drying shrinkage and air permeation resistance. Using BFS sand, concrete infrastructures can be more durable.

This study presents findings related to chloride permeability of several widely used Texas Department of Transportation bridge deck concrete mixtures. The rapid chloride permeability test (RCPT) was selected and seven mix designs were tested; five were evaluated using cores taken from field-cast model bridge decks and the other two from laboratory-cast specimens. Mix designs were selected based on their extent of use around the state, with differences in terms of type of cement, coarse aggregate type, and supplementary cementitious materials. Wet-mat curing durations of 0, 2, 4, 8, 10 and 14 days were evaluated for each mix. Experimental results showed that no significant benefit for resistance to chloride permeability beyond 2, 4 or 8 days depending on the mixture, beyond which the benefits appeared to diminish. A comparison of results obtained from the RCPT and its alternative test; the ponding test, showed a correlation between their results for some mixtures.

The majority of high-rise buildings are designed with one or several underground stories in the urban area. However, many researchers don’t incorporate it in the dynamic analysis assuming that the building is fixed at the ground level. This study aims to investigate the effect of the underground stories on the dynamic response of RC building. This is achieved by comparing the behavior of buildings without underground story with those with multi-level underground stories. In this scope, two dimensional finite element models are generated, where three buildings of 12, 16 and 24 stories resting on loose soil are modeled. The analysis is performed under the effect of a strong earthquake input motion by the use of PLAXIS software. The non-linear small strain hardening constitutive model is employed for an accurate simulation of the soil behavior. Based on the results, the embedded underground stories show a significant alteration of the structural dynamic response. This paper provides recommendations on the importance of including the underground stories during analysis.

Self-compacting concrete (SCC) is a concrete having special features, and is the most revolutionary development in concrete construction for several decades; since every country now faces a problem of skilled labour in construction industry. SCC provides rapid rate of concrete placement and hence faster construction times; it is more durable and also develops high early age strength. The exploitation of natural aggregates is harming environment and thereby necessitating sustainable construction industry. Several alternates to natural aggregates are being investigated to overcome this challenge, and few of them include manufactured aggregates, quarry waste, crushed sandstone aggregates, materials recycled from construction and demolition waste, copper slag, crushed sand from different mineralogical sources, marble and granite waste aggregates, aggregates etc. Research studies demonstrate that these waste or by-products may be used as partial replacement of river sand in concrete. Fly ash - a coal industry waste possessing Pozzolanic properties is highly recommended as cement replacement material for green initiatives. This paper illustrates the laboratory investigation results on SCC incorporating, European Federation of National Associations Representing for Concrete (EFNARC) guidelines, by complete replacement of fine aggregates with Processed Slag Sand (PSS) and partial replacement of cement with Class C fly ash. The results in terms of flow, strength and durability; for this novel SCC when compared with control concrete was found to be highly satisfactory and thereby encourage today’s Engineers to adopt SCC technology with this novel mix combination for sustainable development.

With the advent of tall and complex shaped structures combined with urbanization, the structural designers are posed with a greater challenge to design the structures sustainable to rapid environmental changes. During the design of tall structures, wind loads acting on them are a major factor that needs to be considered. As a pre-requisite, the designer should have the information regarding wind environment of the region, wind forces on the structures and the response of the structure under these forces.For tall and slender structures, across wind effects are more predominant than along wind effects. Recommendations in building codes for across wind effects are very limited. Several experimental studies were made to determine the across wind effects on structures. As wind tunnel tests are costlier and time consuming, an alternative computational fluid dynamics (CFD) approach has been emerged out to study these across wind effects.This paper discusses on the across wind effects on tall structures like rectangular buildings and cooling towers in presence of other interfering structure using CFD analysis in ANSYS fluent. Experimental data of Kim et al. (2015) has been adopted to model the geometry of the structure and to simulate the wind environment around the structure in ANSYS fluent. LES (Large eddy simulations) turbulence model is considered to simulate the desired flow parameters around the structure. This 3D CFD model is validated with the experimental result of Kim et al. (2015). Further, the same scheme has been extended to cooling towers. Across wind effects acting on rectangular buildings and cooling towers are evaluated for the two cases: a. Stand alone case, b. interfering case with the same terrain category. In this manner, the response of the tall structures to across wind loading is studied using computational approach.

Repair and rehabilitation methods for civil infrastructure have become a topic of great interest to engineers, and fiber reinforced polymer (FRP) laminate is one of the most popular and practical solutions for strengthening and retrofitting of concrete structures. Several past studies indicated that significant increase in strength and stiffness can be achieved by using this technology. The quality of the FRP-concrete bond is critical in transferring stresses through the interface, and the in-situ evaluation of the bond strength is still a challenging issue. To quantitatively evaluate the bond strength, non-destructive technique (NDT) using ground penetrating radar (GPR) was utilized on 32 laboratory concrete beams strengthened with carbon FRP (CFRP) laminates. Various parameters that may affect the bond strength, such as surface roughness, voids, epoxy type and thickness, and FRP type, were considered. The experiment was conducted with the objective of non-destructively detecting the parameters. The associated bond capacity of each sample was then found through a three-point bending test and also correlated through finite element modeling. Quantitative relationships between each of the parameters in the study and the associated bond strengths were then developed. The results of this study will be very useful in estimating the in-service bond conditions of applied FRP laminate, thereby estimating the expected strength contribution of the laminate in the overall flexural strength of structural members.

The mechanical properties in terms of indirect tensile stiffness modulus (ITSM) properties and permanent deformation of CBEMs containing new cementitious materials made from activated blend of waste fly ash and inert Limestone filler were investigated. CBEMs were prepared with these fillers, and then these mixtures were subjected to microwave treatment at four treatment time and high power level. The aim was to identify the influence of microwave treatment on the mechanical properties and identify the microwave suitable application time ranges. The papers reports that microwave treatment has significantly improved the indirect tensile stiffness and permanent deformations resistance of all the mixes studied and shows that the mixtures containing the new developed cementitious filler provide high quality materials in terms of both stiffness and deformation resistance which are acceptable by road engineers. More importantly, the new fast curing cold mix asphalt is satisfying the current British standard.

The seismic performance of open frame platform structures which is a complex structure commonly found in large oil refineries is evaluated in this study. Analytical Fragility curves are developed to evaluate the performance of each platform models at Immediate Occupancy damage state after an earthquake. The methodology that were used to develop the curves, are based on calculating axial deformation of the brace member using nonlinear time history analysis for different ground motions with different intensities and frequency contents. The fragility curves are developed based on the acceptance criteria for the brace member given from the FEMA 356. It was found that as the bracing member size increases within the same structural shape, the performance of the structure in reaching/exceeding immediate occupancy performance level decreases. Additionally, as the height of the structure increases the probability of reaching immediate occupancy increases. It was also found that certain structural members are not to be used as bracing members for these structures.

The seismic performance of Pipe Rack structures which is a complex structure commonly found in large oil refineries is evaluated in this study. Analytical Fragility curves are developed to evaluate the performance of each pipe rack models at Life Safety damage state after an earthquake. The methodology that were used to develop the curves, are based on calculating axial deformation of the brace member and the plastic rotation of the moment frame using nonlinear time history analysis for different ground motions with different intensities and frequency contents. The fragility curves are developed based on the acceptance criteria for the brace member and the partially connection moment frame given from the FEMA 356. It was found that as the number of bay increased, the probability of the structure exceeding/reaching Life Safety performance level for the brace member significantly increased and decreased as the number of bay decreased. Similarly, as the number of stories increase, the chance of reaching LS increased, as decreasing the number of stories lowered the change of achieving LS for both moment frame and brace member. It was also found that changing the member size does not have a remarkable effect to their fragility values in Life Safety level of performance.

In this paper, a qualitative approach, selected to estimate the seismic vulnerability index of reinforced concrete bridge piers in terms of ductility is presented. Samples of three bridges that are representative of RC bridges in Algeria were identified to carry out this study. For each structure, the sectional ductility was first computed using a multi-layered sectional analysis program (Extract). Structural ductility values were then obtained with a simplified pushover analysis carried out with a non-linear finite-element program (Seismostract). Then, the ductility demand was obtained from time-history analyses, using six ground motion records for Algiers and its surroundings (Nonlin program). Based on the Priestley theory, the ductility values were then used to elaborate a ductility index to be used as a preliminary evaluation criterion for seismic vulnerability assessment of bridge piers. The calculated ductility demand (required ductility) when compared to the ductility capacity of the selected bridge bents could be used in a seismic vulnerability assessment to identify the seismic behavior of bridge piers and to make a decision as to its safety or strengthening.

The use of composite systems comprising of concrete and conventional steel is commonly used in a multi-story steel frame with hot-rolled steel section. However, the use of cold-formed steel section designed as composite beam is yet to be established. Cold-formed steel (CFS) is usually categorized as a slender section which tends to buckle and deform. The strength of this section is usually reduced significantly as the section is very thin. However, all these problems can be significantly improved by designing the section as composite construction by integrating concrete and steel with the use of rebar as a shear connector. Therefore, this paper presents experimental works on the structural performance of cold-formed steel (CFS) section with self-compacting concrete (SCC) as a composite beam by means of the shear connection mechanism of the proposed using reinforcement bar. A specimen was carried out where the behavior of encased double cold-formed steel composite beam with composite slab was tested until failure. The proposed shear connector of size 12 mm was embedded in CFS and encased in SCC with a compressive strength of 40 N/mm2. The specimen comprised of two parallel CFS attached together to form encased beam with a concrete slab. Based on the experimental results it was found that the proposed composite system using bent-up rebar as shear connector showed slightly higher results than expected with ultimate moment capacity of 358.3 kNm for experimental and 341 kNm for predicted results. The failure mode was recorded as ductile which make it suitable to be used in the seismic zone.

Designers are drawn to a fresh challenge of improving the capacity of military and civil infrastructures in order to protect lives and properties during blast attacks which is becoming frequent in occurrence throughout the world. However, there seem to remain an ambiguity as to the accurate assessment of threat levels associated with any blast case which may be due to shortage in experimental data of blast loading and its effects on structures as a result of cost. This study therefore evaluates the nonlinear dynamic response of a shear wall structure member subject to blast loading. The extent of damage or response of the wall as per stresses, strains, pressures and displacements were effectively measured with the aid of finite element (FE) which is simulated in ABAQUS software. The laminated wall performed better with an average of over 90% improvement over the control wall in all the response categories considered. Also, while the walls may be damaged, the CFRP laminates contains it in order to save lives.

The paper deals with technologies of concrete surface improvement. Concrete surface is important because of its hardness, durability and other problems. Besides, it is necessary to protect it from aggressive environment. The purpose of the article is to introduce a few techniques of silica sol use in order to change concrete surface properties. The absorption, irrigation and watering processes were applied as the techniques. Both silica sol and its mixes with solutions contained Ca(II) were used as the substances. The experimental methods were realized during the study. The experiment results have shown that hardness of heavy concrete and foam concrete surface was increased up to 40–50% and the level of soil strengthening was 0.2 MPa. It means that if silica sol and solutions containing Ca(II) are used the soil strength is increased more than 40–50%.

This study evaluates the formulations for prediction of ultimate shear capacity of steel joints in offshore structures in order to ascertain the safety of the structures in service using First Order Reliability Method (FORM) under the European code, EC3:1,8 (2003), design format. Two modes of failure were considered which depend on the embedding strength of the plates and bolts that influences the joints capacities and the failure due to bearing. It is generally observed that the increase in bolt diameter, bolt strength with corresponding steel grades, fasteners thickness improves the safety of the joints, while undue increases in load on the offshore structure may result in safety reduction, but not collapse. The provision for joints design in structures in EC3 (2003) is very robust and efficient. However, economy commensurate with structural safety can be achieved in the current formulations.

This paper reports the results of laboratory studies on the mechanical and chemical properties of alkali activated fly ash concrete mortar. A new hydraulically bound cementitious material made from environmentally friendly waste fly ash and subjected to physico–chemical activation has been developed in this study. In the production of the new cement, fly ash initially has been activated by grinding the fly ash using mechanical grinding and the addition of FGD and or GGBS. The new cementatious materials containing 35% Ordinary Portland Cement (OPC) and 65% of grinded fly ash. The mix then further activated by the use of NaOH of 4 M molarity. NaOH has been added to the mix at 1%, 2% and 3% of fly ash. Alkali activated fly ash where then subjected to curing at normal room temperature for one day.The paper report the compressive strength of the results at age of 3, 7 and 28 days.Samples shown significant improvement in the compressive strength. The reasons for the development of strength of the new material products was studied and explained using both SEM and XRDF analysis and reported in this study.

Nuclear power plants are considered vital structures for generating electrical energy worldwide. In general, a nuclear power plant structure includes two containments, external and internal ones. The internal containment surrounds the main reactor as a primary shield. Meanwhile, the external containment protects the reactor from external impact loads such as jet crash, as well as being considered as a final shield between the internal of the reactor and the outer environment. This research studies the integrity of a reactor outer containment after being hit by a jet plane. Within the context of the research, an analytical model is generated using ANSYS® software to replicate the hit of the reinforced concrete containment including the circular shell and dome. An existing design of a classical nuclear reactor is used in modeling. Such design considers having the shell and the dome lined with inner steel liner plates in order to minimize the radiation flow to the outer environment in case of accidents. The studied external containment structure is assumed subjected to the impact of a jet plane, Boeing 747-200c. Riera Method is used to simulate the impact load with respect to time at a vertical level of 30 m above the upper foundation level, and at the outer surface of the external shell. Heavy weight concrete is assumed used in the shell and the dome with a compressive strength of about 60 MPa. The impact load is concentrated at 16 nodes at the outer surface of containment. The maximum deformations of the containment structure are studied and especially within the impact region of the jet plane. The containment is found to be stable after the impact of the jet plane, but with having some clear damage to some elements within the region surrounding the impact area and some secondary damages in other locations.

Probabilistic reinforced concrete bridge deck flexural strengthening with Carbon Fibre Reinforced Polymer (CFRP) laminates is presented. Results show that the existing and evaluated deck is in conformity with AASHTO LRFD (2010) specifications and indicate that the composite concrete deck as suggested in formulations meet the requirements for bridge decks and have the ability to sustain more live loads up to about 90% than conventional reinforced concrete decks of the same structural formulations. Also, the initial safety indices observable prove to be traffic dependent as it depends more on the live load. AASHTO design equation that corresponds to a βtarget = 3.5 seems to be overestimated for strengthening purposes. The strengthening with a βtarget = 4.2 as suggested herein provides a better structural reliability than βtarget of 3.5 proposed by AASHTO LRFD (2010) provision and with no significant differences in bonded CFRP amounts required. The optimum thickness of bonded CFRP laminates required is found to be 5 mm for the upgrading of reinforced concrete bridge decks.