Recent Developments in Structural Engineering, Volume 2

An attempt has been made in this study to investigate railroads on geocell reinforced earth beds under static concentrated load. The geocell layer has been idealized as a beam since it is anticipated to have finite bending stiffness. The rail idealized as an infinite Euler–Bernoulli beam has been placed on a compacted granular soil above the geocell layer resting over very soft soil. Winkler springs have been used to model the upper dense and bottom soft soil layers, respectively. Hyperbolic constitutive relationships have been considered to model their nonlinear behaviour. The governing differential equations for the double beam system’s flexural response have been obtained and presented in a non-dimensional form. Finite Difference Scheme in conjunction with iterative Gauss–Seidel technique has been utilized to analyze these equations for suitable boundary conditions. It has been observed that non-linear behaviour of soils has a profound influence on the response of the system and parametric investigations have been conducted to further study the effect of a wide range of parameters.

Bearings are a critical element of a bridge. Although they represent only a small part of the overall structures and the cost too is miniscule, they can potentially cause significant problems if they do not function properly. The arrangement of the bearings too plays a significant role in the proper functioning of the bridge. The present work is pertaining to a repair and rehabilitation of a damaged set of bearings on NH of a ROB in the state of Rajasthan. The bridge is over an active railway line with a span of over 41 m and skew of 56°. The analytical work carried out to identify the root cause of the damage resulted in surprising findings. It was realised that the skew angle plays a very dominating effect on the bearing forces. The arrangement too needed revision. The work under reference is presented in three parts viz., identifying damage, analysing the same and the remedial measure to cure the distress. The purpose of this paper is to understand the behaviour of large skew vis-à-vis the bearings and to propose reliable arrangement of the same to improve load transmission. MIDAS is used as a tool for simulation.

The paper focuses on analysis and retrofitting of a 100-year-old RCC bow-string road bridge in Chitpore, Kolkata. Distresses were noted on the vertical RCC hangers, deck, crossbeams, etc. Based on NDT and visual inspection of extent of cracks and corrosion, material strengths were estimated for different members and analysis was carried out. Accordingly, structural deficiencies were quantified so that a befitting retrofitting scheme can be modelled. Stages of execution using specialised materials have also been discussed.

A Structural pounding is most commonly observed failure when tremor hits the area, that’s happen due to insufficient spacing between the two structural units. Pounding induced a high amount of acceleration pulses which mostly causes the structural failure. In the present paper three elastic and inelastic closely spaced equal heights eight-storey structure in the form of stick spring mass system is studied under surface blast actions. The lateral dynamic loads are applied to the structures considering pounding effect under the presence and absence of soil structure interactions (SSI) at the base considering Winkler spring model. The floor pounding and linear systems are considered for the entire systems under time domain analysis. A single case of three adjacent G + 7 stick systems is formulated and run using SAP 2000NL software for 25 kg blast charge weight and 15 m standoff distance. The results of this MDOF system under surface blast loading are quantified in the forms of time histories of upper floor displacements, upper floor level pounding forces, and base shear forces. The results indicate that displacement response in SSI models is much severe than fixed base system. The inelastic system experiences more displacements than the elastic system. The SSI underrates the base shear values compared to fixed base system and elastic models have developed more amounts of base shear values compared to inelastic system. The increases of blast charge weights have produce more catastrophic effects in the structures under structural pounding. In SSI models the pounding forces are lesser than the fixed base system.

Building behavior in seismic forces is dependent on the structural configuration of the building. Regular buildings have more stable and predicted behavior than irregular ones. Irregular configuration in plan and in elevation is one of the major causes of the failure of buildings during earthquakes. Vertical irregularity is more vulnerable than horizontal Irregularity. In vertical irregularity, the stiffness irregularity below the mid-height of the building is affected more than the irregularity above the mid-height. The Soil Structure Interaction (SSI) effects on the vertical irregularity of the RC medium-rise building are analyzed by using 3D and Lump mass models in SAP 2000NL. In the present study, medium hard strata soil is considered to predict the effect of SSI through indirect methods. In the present paper total of eight models of buildings are considered and studied based on the vertical irregularities criteria of mass and stiffness as per IS 1893:2016. Initially, all lumped mass models are considered as linear elastic with fixed based and SSI effect, later on, the same stick models are converted into the elastoplastic stick models by evaluating the yield displacement and yield strength of the 3D model over pushover analysis. The results of the time domain form are analyzed by considering seismic parameters such as fundamental time period, base shear, and displacement of irregular buildings. It is observed that the 3D model is more difficult to analyze than the lump mass model but results obtained by the 3D model are realistic and much identical to that of the lump mass model. Base shear is observed less for the ground floor double height model and middle floor double height model than the other irregularities. However, the displacement response of the middle floor double height model is observed more than the other building. It has been observed that the stiffness irregularities are affected more in the severe earthquake for the SSI effect.

Although the confined masonry (CM) construction has shown good seismic performance but, in some cases, it has also experienced significant damage. The majority of damages were reported in the walls with openings, due to the absence of appropriate confining elements around the openings. Thus, the in-plane lateral response of perforated CM walls without and with confining elements have been evaluated using experimental investigation. Initially, two perforated CM walls without confinement around the openings were tested under quasi-static in-plane cyclic loading. Thereafter, CM walls having confinement around the openings were constructed and tested under similar loading cycle. The experimental study showed that the presence of tie-members around the openings was highly efficient in enhancing various performance parameters of the CM walls such as its in-plane capacity, energy dissipation, stiffness degradation and strength degradation. It was observed that the CM wall with confinement around window opening was able to achieve the strength more than twice of its respective wall. Further, the cracks were uniformly distributed in the CM walls with confined opening and no major failure was observed in the walls even at higher drift levels.

The review of literature confirms that there is dearth of research studies on relative bending performances of composite skewed stiffened cylindrical roofs. This paper works on this area using a C0 nonlinear FE code. The isoparametric code combines von-Karman strains with constant shear strain and eight noded elements. The reduced integration technique is adopted to obtain the element matrices and the global ones are achieved by combining the element matrices with due consideration to the shell geometry. The correctness of the approach is confirmed through solutions of benchmark problems. The nonlinear deflections and stress resultants of transversely loaded shells are reported for varying skew angles, laminations, and stiffener numbers and orientations. The post-processing of results includes critical discussions to suggest practical application recommendations to practicing engineers which also involve the serviceability criterion.

Buildings that seemed to be sturdy enough could collapse during an earthquake and reveal flaws. The knowledge gained from the most recent earthquakes shows that the majority of structures that collapsed were discovered to be lacking in order to satisfy the standards of the most recent codes. Non-linear static pushover analysis must be executed to assess the performance of tubular structures under anticipated future earthquakes of both new and existing structures. Several scholars have done research involving the evaluation of structure response of various structural system. Hence the pushover study performed by the researchers is anticipated to offer sufficient details on the structural strength and deformation demands placed on the structural system by the design ground motion and comparison with the available capacities at desired performance levels. In the present study, we investigated to identify the most effective structure which increase the lateral stability of the system by examining how a frame tube structure with a haunch girder and braced tube structural system behaves in seismic Zone III using SAP2000. To choose the most appropriate structural system and gauge performance levels, several results like base shear, top story displacement, natural period, and pushover results is compared. It is observed after analysis that braced tube structure is efficient among the structures consider in this study.

Buildings with deficiencies are severely damaged during seismic events. Buildings with multiple irregularities are more vulnerable to earthquakes. Many such buildings exist and are being constructed both in urban as well as rural areas of developing countries. The awareness of the behaviour of such buildings with multiple irregularities during seismic events is less. The earthquake events have demonstrated the failure patterns of the deficient reinforced concrete buildings. Even then the awareness of the behaviour of such buildings with multiple irregularities during seismic events is less. Hence, an attempt is made in this study to analyse the buildings with multiple irregularities using the structural analysis software SAP2000. The irregularities considered in this study are soft-storey and, plan irregularity wherein the center of mass does not coincide with the center of stiffness named as torsional irregularity. Various response parameters such as relative displacement, acceleration amplification, base shear, and torsional responses are evaluated. Failure modes of the buildings with irregularities are studied and the code provisions on seismic performance of deficient reinforced concrete buildings are reviewed.

The present study deals with the seismic performance assessment of ten storey RC building with and without base isolation system under the mainshock and one aftershock of earthquakes. The non-linear time history analysis is carried out in the commercial software SAP 2000 to investigate the seismic behavior of base building frame with Lead rubber bearing. Two ground motions of far field and near field earthquakes and two levels of earthquakes are considered for the analysis. The response parameters of interest are base shear, top-storey displacement and absolute acceleration, number of hinges, maximum inter-storey drift, and isolator displacement. The seismic behavior of the building frame is investigated with the help of maximum and residual responses during and after the MS-AS sequences. Further, it is concluded that (i) the residual responses of the LRB base isolated (BI) frame depend on the level of PGA and are response-specific; (ii) the maximum storey drift is determined to be modest at a lower PGA level; (iii) the pattern of maximum responses in the single aftershock is not appreciably altered by the residual responses after the mainshock in isolated frame.

Tensile diagonal cracking in Reinforced Concrete (RC) beams due to the shear can be brittle and leads to sudden failure. Hence, it is essential to enhance the shear capacity of RC beams so that the failure mode can be converted to ductile flexure. In this work, a novel Engineered Cementitious Composites (ECC) beams prepared using different types of locally available plant fibres are evaluated for understanding their shear behaviour. In total, eight reinforced beams were cast with four different natural fibre types such as flax, hemp, kenaf and pineapple for improving the ductility characteristics. In addition, fibre reinforced polymer (FRP) rebars are used as longitudinal reinforcement to tackle the corrosion issues occurring in the case of conventional steel reinforcement. All the beams were tested in a three-point bending configuration with the shear span (av) to effective depth (d) ratio of 3.2. Results revealed that the addition of natural fibers helped in improving the post-cracking behaviour and ductility of FRP reinforced ECC beams. Moreover, the use of natural fibres in the shear span eliminated the need for transverse shear reinforcement and showed a ductile failure mode. In specific, flax fibres showed greater enhancement in load carrying capacity and energy absorption values when compared to the other natural fibre reinforced ECC beams.

Cold-formed Steel (CFS) lipped channel beams (LCBs), are frequently employed as structural elements for floor joists and bearers in construction. They are usually thin-walled with unstiffened webs and are vulnerable to various types of local and global failures. These failures encompass shear, bending, combination of shear and bending, web crippling and combination of web crippling and bending. Web crippling occurs when these CFS beams are subjected to highly localized loading. The use of finite element (FE) models validated using limited experimental results is a very rapid and economic method to generate large number of results to understand the web crippling behavior of LCBs. Owing to the complex nature of web crippling phenomenon, majority of the literature discusses the use of a quasi-static analysis of FE model based on explicit integration scheme to formulate contact between different parts of the model. But the major challenge of using a quasi-static analysis scheme is to estimate the stable time increment that influence the computational effort and reliability of analysis results. This paper presents the details of a general FEA procedure (using nonlinear static method) and its validation against web crippling test results for different loading cases and flange boundary conditions.

Pounding forces cause severe damage to bridges when subjected to strong earthquake ground motions. Although the pounding force has been considered in previous research on bridges, the effect of frequency-dependent soil-structure interaction (SSI) on seismic pounding has not been considered in most of the studies. Therefore, the present paper aims to study the effect of frequency-dependent SSI on seismic pounding in RC bridges because it has been observed from the literature that the stiffness and damping of soil supporting the structure depend on the frequency of earthquake excitation. Actual earthquake records have been considered, and the results obtained using frequency-dependent SSI are compared with those obtained considering static (frequency-independent) SSI. Analyses results show that consideration of the more refined frequency-dependent SSI model leads to an increase in the natural time period of the bridge-foundation-soil system, resulting in a reduction of pounding force in the bridges. It is also observed from the displacement time history analysis of the contacting lumped masses that the displacements in some cases increase while in other cases decrease for a particular gap size. The study investigates the effect of static and frequency-dependent SSI on the maximum displacement and maximum pounding forces for different gap sizes for soft soil conditions.

Topology optimization (TO) is a design tool utilized during the conceptual phase, aiming to optimize the material distribution within a defined design domain while considering a specific set of loads and boundary conditions. Traditionally TO is employed for solving the problems with the formulation as minimizing compliance that increases the overall structural stiffness. However, from a practical point of view, stress is a significant concern ignored in the traditional compliance-based formulation. So, to make a TO a realistic approach, the involvement of the stress constraint is considered in the optimization formulation. When stress is incorporated into the optimization framework, a significant challenge arises due to the localized nature of stress, resulting in a considerable number of stress constraints. To address this issue, the global stress technique is adopted where stress constraint of each element is aggregated using some aggregation function. The von-mises failure criteria is used, and P-norm formulation is adopted to formulate the stress constraints. The SIMP method is used as an interpolation scheme to penalize the intermediate densities. A standard benchmark L-shape numerical problem is presented to study the influence of stress constraints in the traditional compliance-based optimization formulation. The results show that stress constraint consideration in the conventional compliance-based TO leads to a smooth round corner of the L-shape problem.

In the present study, experimental work has been carried out to investigate the comparative behaviour of two types of metallic dampers consisting of plates yielding under both shear and flexure. The first damper consists of two X-shape plates (added damping and stiffening, ADAS) at both ends and a shear plate in the middle; the second damper consists of a shear plate in the middle and four K- plates on either side of the shear plate. K-plates and X-shape plates were oriented to yield under flexure, whereas Shear plate yield under shear. Performance parameters such as lateral load carrying capacity, energy dissipation potential, and hysteretic performances of these dampers have been investigated and compared. Since X-shaped plates in the first damper were placed outside the shear web, both components act independently. In contrast, K plates in the second damper support the shear plate in the weak direction and reduce out-of-plane buckling, thus giving stable hysteresis.

Spalling in concrete is a phenomenon when concrete shards detach and fall off from the structural members, leading to decrease in the load bearing capacity. Literatures have shown that pore pressure plays an important role in the occurrence of spalling in concrete members. This study discusses the variation in pore pressure when the structural member is subjected to non-uniform heating. The model is developed by coupling the principles of mechanics and thermodynamics to calculate the pore pressure inside normal strength concrete (NSC) member due to non-uniform heating. The results of the analytical model have been validated against the experimental results of uniform heating due to the unavailability of research considering non-uniform heating. Upon validation a reasonable agreement can be observed with the experimental results. Further, a case study of a possible non-uniform heating of structural element has been presented and pore pressure variation has been discussed. It is observed that pore pressure is different for different locations of the compartment with maximum at the start location of fire and minimum at the ends of the compartment. Further, this proposed model can be integrated into any existing modeling framework to study the macroscopic behavior of normal strength concrete members.

In this study, trials have been made for the use of bamboo as a replacement for reinforced concrete members which is simple, efficient, sustainable, and economical for rural constructions. The important aspect of steel used in concrete is tensile strength therefore in this study, tensile strength and modulus of elasticity of split bamboo were found. Bamboo was locally procured, in Gujarat D. strictus type of bamboo is available. A tensile test was performed in a universal testing machine along with a mechanical strain gauge to measure the strain in the bamboo specimen. The main drawback in bamboo while performing tensile tests is slippage during the test because of its smooth surface therefore gripping arrangements were made such that only load was transferred through grips to bamboo specimens without any slippage. Overall six specimens were tested for direct tension test, The modulus of elasticity was found to be in the range specified in IS 15912:2018 for the use of bamboo as reinforcement. Out of six specimens, the ultimate tensile strength was found to be 110 $$\frac{{\text{N}}}{{{\text{mm}}^{2} }}$$ N mm 2 .

Cement is one of the most commonly used materials on earth; however, it is associated with environmental concerns. While the focus of the world is on sustainable development goals, cement is being used with environmentally friendly materials, e.g., metakaolin. There are many available lab test methods for the compressive strength of mortar; however, they are not only expensive and time-consuming but also require thorough quality control. Also, there is a need to find the best consistency before 28 days. Empirical methods and basic regression techniques fail to incorporate the complex non-linear behavior and high number of input parameters of the mortar. The study presents a machine-learning-based simulation model for the prediction of compressive strength of metakaolin mortar using the Group Method of Data Handling (GMDH) and Extreme Learning Machine (ELM) models. For the purpose, a dataset totaling 276 is gathered from the available literature and validated using a Pearson correlation matrix and sensitivity analysis. The best performance of the model is achieved with 15 maximum layer neurons, 4 maximum layers, and 0.6 selection pressure for GMDH. Best performing ELM model is configured for 50 number of hidden neurons. The study concludes that both ELM and GMDH are a robust model for prediction of compressive strength of mortar (R2 = 0.9 for both the models in testing) and can be used as an alternative model once it is trained and tested on the in-situ data results, however ELM closely outperforms GMDH.

In this study, we investigate the impact of the location of door and window openings on confined brick masonry (CBM) walls subjected to lateral in-plane loads. Based on the position of the door opening, three different models of CBM walls were considered and four models were considered when the door was placed in the centre of the wall and the window opening was at different sides of the opening. Using finite element analysis, the pushover curve was determined by using Abaqus software. Each model’s peak base shear (PBS) and initial stiffness (Ki) were determined using the pushover curve. According to the results, PBS increases as the distance between the lateral load's point of application and the opening's corner increases. As compared with DL (door at the left), PBS increases by 6.25% and 20.56%, for DC (door at the centre) and DR (door at the right) respectively and Ki is minimum for central door opening. On the other hand, when considering the window opening position, it was observed that PBS and Ki decreased with an increase in the opening area. The decrease was the highest for DCWLR (door at the centre and windows at both left and right), with a 48.3% decrease in PBS and a 53.1% decrease in Ki compared to DC. This study provides valuable insights for designing CBM walls with openings subjected to lateral in-plane loads.

The objective of this paper is to present a comprehensive review of the current state of knowledge about the impacts of dynamic soil-structure interaction on building structures as well as the modelling tools available to deal with (SSI) effects. SSI occurs when the movement of the ground during an earthquake affects the behavior of the structure. The stiffness and damping properties of a structure could be altered by it, which may consequently influence the structure's reaction to earthquake forces. Performance based seismic design with SSI takes these factors into account and seeks to optimize the performance of the structure during an earthquake by adjusting its design parameters. This paper provides and discusses an overview of the associated research and findings. The article includes relevant research and conclusions and the primary methodologies to evaluating soil-structure interaction problems using frequently employed modelling tools and computational techniques. SSI's participation in numerous design regulations and global recommendations is also specified. Current advances and observations on the impact of SSI on seismic response of structures with various structural systems and foundation designs are considered. Furthermore, in order to assist new researchers in improving prior discoveries, unexplored areas of research and emerging directions for future research trends in SSI area are identified.

The present study uses a computationally efficient optimization algorithm to determine the optimal location and the number of sensors for state estimation. A ten-storey shear building frame located in Surat city having magnetorheological (MR) damper at the first, second and third floors is considered in the study. The building frame is subjected to response spectrum-compatible ground motion time histories generated using SeismoArtif software. The far-field and near-field earthquakes ground motions are generated considering different soil conditions, namely class A, B, and C for seismic zone III as per IS 1893:2016 (Part-I). The Linear Quadratic Gaussian (LQG) controller along with clipped optimal control algorithm is employed for generating the MR damper force. The study results show that the optimized number of sensors remains the same for the earthquake considered in this study. Further, the optimized location of sensors varies with the earthquake.

Phase-field models (PFMs) have been demonstrated to accurately predict complex crack patterns such as crack branching, and merging. However, these models come at a significant computational expense. We propose an adaptive mesh refinement (AMR) algorithm in the present study to efficiently solve the thermomechanical fracture problem. This investigation focuses on three widely recognized PFMs—AT1, AT2, and PF-CZM, to implement them in a single codebase, and utilize them to investigate the effectiveness of the AMR algorithm in solving the thermomechanical fracture problem. We analyze the five different stages of mesh adaptivity, including Solve, Estimate, Mark, Refine, and Check. The adoption of the mesh adaptive algorithm results in a substantial reduction in the total simulation time, ranging from 5 to 90 times faster, contingent upon the type of the problem, in comparison to simulations employing non-adaptive mesh refinement a priori.

All civil engineering structures should withstand a certain level of ground shaking from earthquakes without sustaining significant damage to avoid human and economic loss. Ground shaking hazard at a particular site can be estimated by seismic hazard analysis. Completeness analysis of earthquake data is a pre-required process of seismic hazard analysis. This study attempted to prepare a homogenized earthquake catalogue for Nagpur city. This involves the compilation of earthquake data from various agencies, spanning from 1800 to 2020, within a 400 km radius of the centre of Nagpur city. Further, to follow the poissonian model of earthquake occurrence, this earthquake catalogue is treated for declustering analysis. A completeness analysis is conducted to determine the time interval in which the earthquake data is considered complete for various magnitude class, using two most common method i.e. Stepp and Cumulative visual inspection method (CUVI). The common earthquake data from both the two methods are extracted and can be used a final earthquake events for the hazard analysis and other seismological studies. From the completeness analysis, it has been observed that the data for the magnitude range of 3.0 ≤  MW ≤ 4.0, 4.1 < MW ≤ 5.0, and 5.0 < MW is complete for the last 24, 57, and 94 years. This study will help to understand the distribution of the earthquake data in the Nagpur region. Also, seismic hazard analysis of Nagpur city can be performed using the earthquake data of the complete catalogue.

The expansion of urban areas has resulted in a scarcity of land in metropolitan regions, leading to various transportation challenges. Constructing underground structures has proven to be a highly effective solution to these issues. However, tunnels can experience deformation from different types of loading, such as static load and dynamic load. Especially, when tunnels are built in geologically unstable formations, it becomes crucial to prioritize evaluating potential failure caused by the stresses they encounter. This research assesses the deformation behaviour of tunnels in terms of the magnitude resulting from static loading, including the scenario when different rock materials exist in the tunnel span. First, a finite element simulation model is developed and validated with experiments, and then it is used to examine the behaviour of lined Circular tunnels with different layer strata. In this investigation, the rock's unconfined compressive strength is used to provide maximum vertical loads to the tunnel lining. In the simulation model, Mohr–Coulomb Plasticity model is applied for different rock types. The findings indicate that the deformation characteristics of tunnels are influenced by the presence of layered strata within the tunnel span and can be used to predict the deformation curves for tunnels.

Ideally, we do not know that when and where earthquake will occur so that many stations are instrumented to record the ground motion. Many more records have been obtained in regions where moderate ground shaking occurred. Earthquake is a natural phenomenon which occurs anytime there are regions where the earthquake occurs frequently. When an earthquake ground motion occurs, it consists of three translational and three rotational components of motion. We need to safeguard the buildings from earthquake for that we must do a thorough study about torsional and rocking components so that humans and lifeline structures are safe against earthquake. We have three translational components which can be studied by an instrument. Accelograms are meant to study the earthquake ground motion. Accelerograph is the instrument to record the three translational components of ground shaking. Transducer is the basic element of an accelograph. However there are no instruments developed to record torsional ground motion.in the present study after a critical review of the various method a simple method has been identified for generation of torsional response spectra from the response spectra of the recorded translational accelerograms for use in practical engineering application. The application of the identified method has been illustrated for recorded translational accelerograms in Himalayan region. A normalized standard spectrum is developed for the torsional ground acceleration in the region.

The majority of existing buildings in any urban environment are self-styled buildings with varied construction practices. Most of the time these are built without any consideration for the seismicity of that location. Therefore become vulnerable building stock in case of any eventuality, paving the way for a disaster. The damages caused to buildings and the causalities resulted thereof during past earthquakes (Bhuj (2001), Sikkim (2011), Nepal (2015), Turkey (2023), etc.), are the epitome of this disaster. In view of this scenario, active research has been focused in this direction resulting in several updates of seismic provisions in order to provide a safe habitat. However, in order to visualize the vulnerability of existing buildings in comparison with the latest seismic provisions, the reliability of performance needs to be evaluated with code revisions. Hence, an attempt has been made to analyze the comparative reliability assessment of the performance of an existing building designed for more than a decades in accordance with IS:1893–2002 and IS:1893–2016 regulations. In the present study, the structural performance of the selected building has been evaluated in terms of the reliability index for the chosen limit state. Nonlinear static analysis is carried out to envisage the structural capacity and performance point of the building in accordance with IS:1893–2002 & 2016. From the analysis results it can be clearly emphasized that the reliability of existing building performance decreases with time. However, reliability of structural performance has shown significant increase with improved seismic regulations. Hence, the deficient structural components need to be repaired / retrofitted in accordance with latest codal provisions to ensure the structure to remain safe & functional.

Residual stresses are thermal stresses that arise in materials during manufacturing processes like uneven cooling, flame cutting, and welding. The manufacturing technique used for steel sections affects the levels and patterns of residual stress, which consequently impacts the strength against Lateral Torsional Buckling (LTB). This research investigates how residual stress influences the calculation of LTB strength in web tapered welded I-beams. Specifically, a simply supported and unrestrained beam with a length of 3700 mm is examined under destabilized loading conditions with varying taper ratios. The study also considers standard residual stress patterns obtained from existing literature, highlighting that LTB failure tends to occur at lower moments for web tapered welded I-beams. By comparing and discussing the results of Load-Lateral displacement and Load-vertical displacement for different taper ratios, this study provides valuable insights. Ultimately, these findings contribute to the future advancement of numerical simulations for asymmetrically tapered welded I-beams.

Steel slag emerges as a residue when molten steel undergoes elimination from impurities in furnaces. The calcareous, siliceous, and ferrous cementation properties of steel slag are significantly influenced by its composition. This study investigates how the addition of steel slag alters the characteristics of mortar and concrete. However, its broad use in the cement and concrete industries is constrained by the prolonged initial setting time and poor early strength. Several studies assessed how steel slag particles affected the compressive strength and early setting times of cement mortar. Also, the effectiveness of steel slag in enhancing compressive strength and initial setting was assessed. The study would assist decision-makers in using steel slag as a resource to partially replace cement. Compared to other binders, steel slag has a higher density. Examining the relationships between the influencing factors and their respective contributions to the enhancement of steel slag properties is a difficult task. The physical characteristics of steel slag provide the concrete with more tensile strength. Reusing steel slag for construction purposes offers positive environmental effects. A systematic review has been presented in this paper. With keen interest, the advantages, limitations, and future application of the study have been addressed.

Mining of atomic minerals is a crucial activity that finds its application in various industries, including the strategic sector. This study analyses a situation where mining activity close to the canal bank (man-made water body) designated as National Waterway-3 (Kottapuram to Kollam, Kerala) affects the bank’s structural stability. The canal is 2.4 km long with an average width and depth of 30 m and 4 m, respectively. The mining operation involves HEMM (Heavy Earth Moving Machinery), heavy equipment, personnel, etc., and the stability of the bank may be impacted by static and dynamic loads as well as water pressure toward the bank. As the cross-section of this land-aqua configuration is an immediate interaction of soil and water, the hydrostatic pressure from both entities was computed at different depths. It is estimated that the static water pressure towards the soil is 39.24 kN/m2; from the soil, it is 69.32 kN/m2 at a depth of 4 m. Littoral drifts and horizontal thrusts will also exert pressure on the canal banks, making them prone to collapse. The paper discusses structural stability from the perspective of near-water mining, paving the way for policy-makers and competent authorities to develop policies and guidelines. Overall, the paper provides a glimpse of mining activity up to the canal bank and discusses measures to maintain structural stability.

The anchorage zone is the most crucial part of a post-tensioned concrete beam, and designing the reinforcement for the anchorage zone requires careful consideration. To design reinforcement in the anchorage zone, it is necessary to evaluate the bursting force, which can be calculated using equations provided in different design codes. However, modeling the actual anchorage plate remains a challenging task to correctly estimate bursting force. To overcome this issue, an anchorage zone with a three-strand multi-rectangular anchorage plate was analyzed in 3D using Finite element-based software to calculate the bursting force. A parametric study was conducted by varying the eccentricity (e) and anchorage ratio (k), and the resulting variation of transverse tensile stress, stress contour plot, and bursting force for the given plate was presented. The findings were also compared with the IS 1343 and AASHTO standard.

Poor performance of buildings with poor plan geometry evidenced catastrophic failure during past earthquakes. Mostly, such buildings have re-entrant corners having different ranges of projection. Therefore, building codes defined limits for projection based on normalised projection length (e.g., India and Venezuela) or normalised projection area (e.g., Eurocode and Venezuela). An attempt is made to understand the effect of the projection on 5-storey H-shaped symmetric buildings by varying the projection ratios (10%, 16.7%, and 25%). Buildings are analysed, designed, and detailed using IS 456, IS 1893(1), and IS 13920, respectively. The inelastic behaviour (based on nonlinear static analysis, NLPoA and nonlinear dynamic analyses, NLTHA) of these buildings are studied using ETABS and Perform 3D. Structural element damage is estimated at the performance point of NLPoA and nonlinear dynamic analysis at maximum considered earthquake. Buildings designed with 10% projection show limited damage compared to 16.7% and 25% projections. Also, limiting only the projection ratio may not help contain the poor performance of buildings with different plan geometry.

The dynamics of slender systems in three dimensions (3D), such as household objects, monuments, obelisks, and sculptures, are highly nonlinear and complex. The current investigation examines the applicability of a recently evolved physical model (PM) with mass-eccentricity for base excitation normal to the plane of eccentricity. The PM is simulated, combining distinct subsystems maintaining proper kinematic conditions in the Simscape Multibody Library. The rigid block is supported at its four corners by four very small spheres. The virtual plane that follows the linear visco-elastic Kelvin model is used to simulate the contact interaction between the rigid base and the body. A comparison of the results obtained from the PM to those by numerically solving a complex set of analytical equations for asymmetric rigid blocks in 3D is found to be in good agreement. For unidirectional excitation normal to the plane of the eccentricity, it is remarkable to note that the residual displacement and rotation of a 3D mass-eccentric rigid block is non-zero as the excitation expires. However, such residual responses are essentially zero for symmetric systems indicating that the block returns to its initial state unless overturned. The overturning spectrum for an out-of-plane rigid block is constructed and compared with that for the symmetric block. The physical model (PM) can be used for general asymmetry and help view the motion for a deeper insight into the intricate dynamics.

Tuned mass dampers (TMD) are widely used in buildings and other structures to reduce earthquake and wind-induced vibrations. However, the application of TMD in wind turbine (WT) structures is limited. Literature shows that the TMD for WT is designed to reduce wind-induced vibrations. However, with the increased popularity of WT in seismically active regions, TMD can be effectively used to mitigate earthquake-induced vibrations. Hence, this study optimizes TMD for WT structures by considering the near-field (NF) and far-field (FF) ground motions. The numerical investigation is carried out for WT structures using OpenSees software. The nonlinear dynamic analysis is performed, and the WT structure responses are compared for multiple TMDs, single TMD and without TMD structure. The mass of TMD and locations are optimised for serviceability and limit the state of collapse.

Inclined wheel loading significantly affects pavement structural responses, including increased stress–strain, rutting, and accelerated pavement deformation. Most of the studies consider tire-pavement stress distribution under static load in the design process. Literature indicates that, as of now, the stress distribution during the turning traffic is reportedly different from the real condition. In this study, a computational three-dimensional (3-D) finite element (FE) modeling was undertaken to investigate the influence of tire inclination angle on pavement structural responses. FE modeling tool ANSYS is used to develop a 3-D tire-pavement interaction model. For the FE simulation, pavement layers including cement-treated sub-base, cemented base, and soil subgrade were considered isotropic linear elastic. The behavior of the bituminous layer material was modelled as a viscoelastic material. Three sets of wheel loading parameters were considered for a standard axle load of 80 kN with a tire pressure of 650 kPa; the tire tilt angles varied between 0°, 4°, and 8°. The findings from each set were compared and consisted of maximum shear stress and vertical strain. The result showed that the contact pressure was substantially higher under inclined wheel loading than under static loading. In line with the results, inclined wheel loads caused the maximum shear stresses and vertical strains. Moreover, this approach can be considered a new approach for more realistic tire-pavement contact modeling of a more comprehensive pavement structure.

Ultra-high performance fiber reinforced concrete (UHPFRC) has gained popularity for high-strain rate applications due to its high compressive and tensile strength along with high toughness and better durability. Such applications require robust material models that can simulate extreme response under complex loading conditions. Behavior of concrete under high strain rate loading, such as blast or impact, is complex, and hence calibration of material model becomes an important factor. In present paper, four concrete material models, i.e. Karagozian and Case concrete (KCC) model, continuous surface cap (CSC) model, Homlquist-Johnson-Cook (HJC) model and Riedel-Hiermaier-Thoma (RHT), were investigated for simulating the behavior of UHPFRC in LS-DYNA. The key parameters of each material model that govern stress–strain behavior were identified and calibrated through single element analysis using uniaxial stress–strain behavior in compression and tension. The calibrated material models were used to compare static compressive and tensile stress–strain behavior of UHPFRC against experimental data. The ability of the calibrated material models to capture response of UHPFRC was investigated through high-velocity impact test on UHPFRC specimen. Finally, based on current findings, it was recommended that the calibrated material models KCC and RHT are suitable for simulating UHPFRC behavior under high-velocity impact.

The concrete structures are exposed to resist the chemical attach, environmental impact and different types of abrasions. These attacks are resisted only if concrete had adequate durability. One important cause for reduction of durability is carbonation in the concrete. Hence, carbonation of concrete is a serious issue. Calcium carbonate is produced when carbon dioxide, water, and calcium hydroxide react, These reactions are continue with the time hence, depth of the carbonation increases with time. It is the difficult to predict the exact depth of carbonation in concrete. In this paper, the depth of carbonation in the reinforced concrete structure was predicted using the electro-mechanical impedance technique. The impedance of a structural system is constant. It is changed if stiffness of the structural system changes. As a result, the system's impedance changed as carbonation depth increased. COMSOL Multiphysics 5.5 was used to simulate a beam with dimensions of 2000 × 250 × 200 mm. Carbonation depth in the concrete was modelled using basic carbonated material properties, ranging from 1, 2 and 5 mm depths. The impedance signature of the uncarbonated modelled beam was extracted. The model was incorporated varying carbonation depths and impedance signatures were determined for each depth. Noticeable changes occurred in the impedance signature for each level of carbonation. Calculating the root mean square deviation (RMSD) for each depth revealed significant changes, even with a short 1 mm depth. This suggests that electromechanical impedance can accurately predict carbonation depth in concrete, highlighting its potential as reliable technique.

The seismic design of steel moment resisting frames (MRF) is normally based on strong column-weak beam philosophy with the beam-to-column connections designed to have a resistance larger than the plastic moment of resistance of connected beams. This approach results in full-strength and rigid beam-to-column connections with the dissipative zones to absorb input seismic energy located in the connected beams. Modern seismic codes also allow the design engineers to use the partial-strength and semi-rigid beam-to-column connections with their resistance lower than the beam capacity and thereby allowing the dissipative zones in the connections. The seismic response of steel moment resisting frames with partial-strength connections is largely affected by the flexibility of connection components. The analysis and design of structural systems in such cases therefore shall properly include the important characteristics of the connection such as the strength, stiffness and ductility in the mathematical model. The paper presents the seismic assessment performed for a steel moment frame provided with partial-strength connections. Beam-to-column connections with extended end plates are used. The characterization of steel beam-to-column connections through moment rotation curves was done using the component method prescribed in Eurocode-3 along with the component based finite element analysis (CBFEM). The seismic demand and capacity calculations were done using the nonlinear static analysis. The assessment shows that the partial-strength connections possess sufficient ductility to enable the structure to reach the drift limits proposed in modern seismic codes.

It is well-conceived that the conventional force-based or displacement-based seismic assessment procedures of structures cannot fully reflect the associated energy-dissipation characteristics of systems. For a structure to be in a safer state, the energy dissipation capacity should be more than the input energy imparted by the earthquake load. Thus, using this energy-based concept, one can assess the seismic performance of a structure more realistically. For this reason, there is a growing trend among researchers to explore energy-based seismic performance assessment techniques on structures. However, most such studies consider reinforced concrete (RC) frames with and without conventional brick masonry in-fill, modelling as equivalent diagonal strut. But, in the civil engineering industry, autoclaved aerated concrete (AAC) blocks are becoming more popular than conventional brick masonry, owing to their lightweight, which enormously reduces the seismic force. But, study on seismic performance assessment with AAC blocks is relatively scarce in the existing literature. Available approaches apply nonlinear static pushover analysis (NSPA) to study the behaviour of AAC in-filled frame under earthquake load. However, as mentioned, the energy-based assessment approach may reveal more detailed seismic characteristics of AAC-infilled structures. Thus, in the present study, an energy-based modal pushover analysis (EB-MPA) is carried out for AAC-infilled buildings. The results are compared with the bare RC frame and brick-infill concrete frame. A comparison of results is also made with that obtained by the MPA method. The responses of the frames are compared by EB-MPA as well as nonlinear static modal pushover analysis (MPA) approaches.

In recent years, horizontally curved steel I-beams have become increasingly popular due to their use in modern buildings and highway bridges. However, the curvature in these beams create stability issues and significantly reduce the beam’s capacity. Moreover, the second-order effects become more pronounced as the curvature increases, leading to the fact that the curved beams carry relatively lower loads than equivalent straight beams. Therefore, it is crucial to accurately estimate the design capacities of such beams by appropriately accounting for the effects of curvature. An essential part of estimating the ultimate strength of beams using material and geometric nonlinear analyses is the correct assumption of initial residual stresses. The magnitude and distribution of residual stresses formed from hot-rolling or welding play a vital role in determining the imperfection factor to be used in the design strength equations. Whether heat-curving or cold curving, the curving process is further expected to change the assumed magnitude and distribution of residual stresses used in the beam design equations. However, current provisions in various international standards adopt the same residual stress pattern as that of straight I-beams for curved I-beams. Therefore, the present work incorporates the few scarcely documented residual stress patterns in literature for heat-curving as the initial stress state of the unloaded beam into finite element models. The studies compare the capacities of girders with these documented residual stresses for heat-curved I-beams with the capacities of the beams with assumed residual stresses typically assumed for equivalent straight I-beams. This paper highlights the need to measure experimentally the residual stresses formed due to heat-curving and its impact on estimating the strength of horizontally-curved I-beams.

Probabilistic and deterministic seismic hazard assessment (PSHA and DSHA) are distinct methodologies utilized for estimation of the seismic hazard at a specific site. PSHA provides a probabilistic estimate of the hazard that could occur at a site, over a certain period of time, considering all possible seismic sources in the vicinity, while DSHA provides a deterministic estimate of the hazard that could be experienced at the site, resulting from a particular earthquake scenario. Hence, one should be careful while comparing the outcomes from PSHA and DSHA, as they represent different approaches to seismic hazard assessment with divergent underlying assumptions and limitations. Failing to recognize these differences may result in a misinterpretation of seismic hazard. Therefore, an attempt is made in this study to obtain a more comprehensive understanding of seismic hazard and to appreciate the strengths and limitations of PSHA and DSHA. The seismic hazard computation is focused on the North-Eastern region of the Indian subcontinent. The PSHA results considering logic tree approach and GMPE rule, as reported by Gurjar and Basu [Gurjar and Basu in Pure Appl Geophys, 2022;Gurjar and Basu in Pure Appl Geophys, 2022;] are utilized for this purpose. DSHA is performed in this study, using a logic tree approach, and the weighted mean representation of hazard spectra from 50th percentile (median from GMPE) DSHA is compared with weighted mean and fractile (from distribution of the intensity measure) representation of UHS from PSHA at different return periods. Contour maps representing the weighted mean hazard are provided for soil site class B and two different time periods.

Residual stresses are known to affect beam flexural strengths and column compression strengths when they are of intermediate lengths, which are susceptible to both yielding and member buckling. The spectrum of research data available for the influence of residual stresses on inelastic shear strengths has yet to be widely disseminated. Residual stresses caused by welding or hot-rolling of steel cross-sections are implicitly considered in design strength equations via empirical factors. These factors are based on idealised patterns and magnitudes in literature, which not only have a wide scatter but are also largely outdated and overly conservative. Since residual stresses ensue from the fabrication process of cutting and welding, the adoption of any advanced fabrication technology necessitates the accurate measurement of these locked-in stresses. This paper discusses the measurement of residual stresses and their influence on the ultimate shear strength of welded I-sections. The residual stresses are measured through a semi-destructive blind-hole drilling method. These measurements are made on slender-web hybrid mono-symmetric welded I-sections. The I-sections are fabricated from plates cut using CNC-laser cutting technology from hot-rolled sheets. CO2 MIG welding is used in welding the flange and web plates.

This study focuses on investigating the use of cement-grouted bituminous mix (CGBM) as a composite pavement material. CGBM is composed of an open-graded porous bituminous mix with an air-void content ranging from 25 to 35%. The main objective of this research is to determine the optimal proportion of cement and fly ash in CGBM to achieve enhanced performance and sustainability. To achieve this objective, various proportions of fly ash-based cementitious grout were used in the preparation of CGBM samples. The fly ash replacement levels included 0, 20, 25, 30, and 50%. The experimental investigation involved conducting tests for compressive strength, Marshal stability, and modulus of rupture to evaluate the effects of partial cement substitution with fly ash on the characteristics of CGBM. The results of the study indicate that the 75:25 mix proportion of cement and fly ash exhibits acceptable strengths in CGBM. This means that the desired performance requirements can be met by replacing 25% of the cement with fly ash. Furthermore, the incorporation of fly ash in the mix offers additional benefits beyond strength enhancement. It reduces construction costs by minimizing the need for cement and contributes to the environmental sustainability of CGBM pavements. This substitution not only decreases the carbon footprint associated with pavement construction but also promotes the utilization of industrial waste, aligning with sustainable practices.

The poor tensile strength and brittle nature of cementitious composites restrict their use in civil engineering. The addition of fibres strengthens and increases the ductility of the composites. The random distribution of fibres in concrete prevents the initiation and propagation of cracks in concrete. In this study, experiments were conducted to assess the mechanical and fracture properties of a composite reinforced with polypropylene (PP) fibres. In the proposed study, polypropylene fibre with a cut-length of 12 mm is used to create composites. Five different PP fibre volume fractions 0, 2, 3, 4, and 5% were used. Cubes, modified briquette, and single edge notched bend (SENB) specimens were casted. The fracture properties of composites have been assessed in the current work using closed loop servo-controlled system. In order to get the load versus crack mouth opening displacement curves and to assess fracture toughness, the test was carried out under displacement control. Compressive strength, tensile strength, and fracture toughness tests were assessed on the composite specimens. The findings showed that PP fibres significantly enhanced post-peak behaviour and fracture toughness in a composite.

Morphing structures are structures that change shape or state to change their operating characteristics or respond to changes in environmental conditions. Thin unsymmetric cross-ply fiber reinforced composites exhibit multiple stable shapes as they are cooled from the curing temperature to room temperature due to induced residual stresses and geometric nonlinearities involving significant out-of-plane deflections. Such composites exhibit dramatic snap-through instabilities when transformed from one equilibrium position to another if triggered with force, piezoelectric materials like Microfiber composites (MFC), Shape Memory Alloys, or any other stimuli. As both shapes are stable in nature, they do not require any additional holding forces to maintain a particular shape making them attractive for applications in deployable and morphing structures. Although the snap-through process is an inherently dynamic process that encounters instability after the limit point, it has been demonstrated earlier that a complete quasi-static transition between the two stable shapes can be alternatively achieved by suitable loading strategies. In this work, we explore suitable loading mechanisms to can lead to a quasi-static snap-through by means of external moments. A new strategy is suggested, where the composite is first subjected an inward moment in two opposite edges, and then opposite moments are applied to the other orthogonal edges. Through our alternative multi-loading strategy proposed in this work, we have obtained quasi-static snap-through, thus circumventing the instability process. We further carry out an extensive parametric study to explore how such quasi-static transitions evolve with change in fiber orientation angles in fiber reinforced composite laminates.

Dynamic response of discrete structural system can be well understood by acceleration measurement under free vibration. Sophisticated piezoelectric based accelerometers are employed for precise measurement of acceleration observed by the mass of the system to the dynamic excitation. However, displacement of the system is a key response parameter for determining internal forces and amplitude amplification of the dynamic system. These warrant double integration of acceleration signal measured for the system. First integration of acceleration signal gives velocity signal contaminated with ramp (slope) with respect to zero mean line due to presence of constant term of the integration affected by DC bias. Further integration to obtain displacement signal leads to polynomial divergence from zero mean line resulting in to error in numerical solution of discrete structural system. In the present study, a simple modified method of double integration is proposed to eliminate ramp and second order polynomial from velocity and displacement signals, respectively on integration of acceleration signal. The proposed algorithm uses band-pass filter multiple times on measured acceleration response of discrete structural system and truncates few initial data of filtered signals to arrive at the peak value. They are further integrated to have constant term of integration zero. The efficacy of the proposed method is established by correlating displacement response obtained through proposed algorithm with analytically obtained displacement response under free vibration with known initial conditions obtained from truncated measured signals for discrete single degree of freedom (SDOF) system at the laboratory. A good agreement with high order of co-efficient correlation, 0.99 is achieved for experimentally derived and doubly integrated displacement signal with that of analytically obtained displacement response of SDOF system.

Floating breakwaters (FBWs) have emerged as a promising solution for mitigating wave energy in an environmentally friendly manner. These structures, which have minimal interference with water circulation, fish migration, and sediment transport, are gaining popularity due to their reduced use of concrete, resulting in lower carbon emissions during construction. However, their effectiveness in attenuating longer wave periods, especially in adverse environments near sea reefs, has been a challenge. To address this issue, a research study was undertaken to modify a double row rectangular FBW, measuring 20 m × 10 m × 4 m each, by incorporating 12 square pores, each measuring 1 m × 1 m, arranged with six pores in the free body and six in the draft portion, resulting in a 15% porosity on the front face exposed to incident waves. These pores penetrate throughout the width of the FBW, and the hydrodynamic response of this modified porous FBW was investigated using ANSYS AQWA software, and the results were compared with a double row non-porous rectangular FBW. The findings of the study were remarkable, showing a significant reduction in wave transmission coefficient during long wave periods of 5, 6, and 7 s for the 15% porous double row FBW. Additionally, the weight of the FBW was considerably reduced due to the porous design, leading to a reduction in concrete mass and associated CO2 emissions during construction. Furthermore, other performance indicators also demonstrated significant improvements.

Demolition waste generated in construction work and its management is still a serious challenge for construction industry. The promising way to solve this problem is recycling of demolished waste and used it as a construction material. Therefore, the objective of present research work is also oriented towards the utilization of recycled demolished waste aggregate (rDWAs) in self-compacting concrete (SCC). In this study attempt was made to evaluate the impact of substitution of natural coarse aggregates (NAs) with recycled demolished waste aggregate along with steel fibres on mechanical properties and durability properties of self-compacting concrete. Optimization techniques were used to design the experiments. Central composite design (CCD) in addition with response surface methodology (RSM) is used for optimization. Optimized conditions for various properties were shown in results obtained from central composite design. The results of this study revealed that rDWAs can be replaced NAs in self compacting concrete and help in management of solid waste.

The effect of explosion on an above-and under-ground structure is rapidly gaining attention from the research community in past years. However, the majority of studies simplify the testing conditions by considering the shape of the explosive as spherical. Certain pertinent studies have proved that the shock waves generated by spherical and non-spherical explosive charges are distinctly different. However, these studies essentially consider free-air blast conditions and not buried explosions. Since the blast mechanisms involved in these two scenarios are vastly different, the variation laws derived from studies on free-air blasts cannot be applied directly to buried explosion conditions. Thereby, this study aims to investigate the effect of the shape of buried explosive charge on the blast wave propagation and shape of the crater. Two shapes of explosive charge are considered in this study: spherical and cylindrical [with varying diameter-to-length ratios (D/L)]. The results show that while the spherical charge produces an isotropic shock waveform, cylindrical charges with varying D/L ratios generate an oblong-shaped waveform. The shape of the shock wave gets elongated along the axis of the cylinder as the D/L ratio reduces, however, the magnitude of pressure decreases. Though the variation in the shape of explosive charge has a significant effect on the blast wave propagation, it has minimal effect on the shape of the crater.

In this work, the adverse effects of an observer design have been investigated by viewing the control of a selected set of modes of a multi-degree-of-freedom structural system, based on a recently developed linear frequency adaptive control algorithm. A closed-form expression that incorporates the observer has been developed using a Luenberger observer based on the adopted control mechanism. The robustness and stability of the new control algorithm due to the observer are assessed through a numerical example of a multi-degree-of-freedom system subjected to external excitations. The dynamic response parameters such as floor displacement and floor acceleration are studied for the performance assessment of the structural system.

The interaction between soil and tunnel lining is an important factor affecting the performance of underground tunnels. In numerical analysis, interface elements are used between different materials to analyze soil-structure interactions and to capture normal and shear stress transfer across discontinuities between two dissimilar material components. PLAXIS software uses “zero-thickness” interface elements between the soil and structural components to simulate soil-structure interactions. These elements introduce a factor that reduces the strength and stiffness of the soil at the contact point. In this paper, plane-strain analysis of a typical section of Delhi-Metro underground tunnels has been performed. Interaction between tunnel and surrounding soil has been considered using interface element. The static and dynamic responses of the soil-tunnel system were evaluated in terms of induced displacement in the soil -tunnel system, induced forces, and bending moment in the tunnel liner. For dynamic analysis, the earthquake’s transverse component (horizontal component) was applied at the base of the model. Viscous absorbent boundary conditions were used to represent the displacement conditions along the vertical boundaries. The interface condition between the soil and tunnel plays a significant role in seismic analysis. The strength parameter of the interface and soil is related to the reduction factor (Ri). The value of Ri varies from 0 to 1. Ri is 0 for the full-slip condition and 1 for the no-slip condition. If Ri is between 0 and 1, relative slip is allowed between the tunnel and the surrounding soil. After analysis, it can be concluded that axial force in the tunnel liner increased with increase in value of Ri, whereas an increase in the value of Ri leads to a reduction in shear force and bending moment. Similarly, displacements, both in soil and RC liners, have decreased with an increase in the value of Ri, and maximum values of displacement have occurred for full slip condition (Ri = 0).

This study delves into examining the flow and viscoelastic properties of soda ash and hydrated lime-activated slag mixes with the introduction of sulfonated naphthalene-formaldehyde (SNF) as a superplasticizer. Three different mixing techniques were employed: standard one-part normal-mixing (NM), pre-mixing soda ash in water (PM), and a dry mixture of granulated blast furnace slag (GGBFS) with a NaOH solution (CM). Without SNF, the yield stress followed the order CM < NM < PM. The optimal percentage of SNF varied depending on the mixing technique: 0.75% for NM, 0.5% for PM, and 0.25% for CM. Adding the right amount of SNF reduced the yield stress in all mixing methods. However, it increased the storage modulus, indicating improved structural integrity. None of the samples displayed a distinct low-velocity elastic response (LVER) plateau.

The behavior of the concrete piles subjected to lateral load depends on subsoil conditions, sectional properties of the pile, and boundary conditions of the pile at the top and bottom. This paper investigates the application of artificial neural networks (ANN) to predict max deflection, max bending moment, and max soil reaction of laterally loaded concrete piles on various soil conditions. The data used in the ANN model consists of various inputs such as dimensions of the pile, material properties, loads, and soil properties. The ANN models are trained using 70% of the data, and tested and validated using the remaining 30%. The data required for ANN training was generated after numerical analysis using the Subgrade Reaction Approach on discrete concrete piles. Numerical analysis of the pile model using the subgrade approach is confirmed with manual calculation as per IS: 2911(Part 1/Sec 4)-2010. This paper investigates the capability/usefulness of ANN to monitor the response of a laterally loaded concrete pile for different soil conditions. From observing results, show very negligible deviation between computed results by the Subgrade approach and ANN results.

Brick masonry is one of the most widely used building materials worldwide, including in India. Globally, the strength and stiffness of clay brick vary from region to region. Most of the experimental and numerical analysis in the literature covers masonry with strong brick and weak mortar, where failure is characterized mainly at the brick–mortar interface. However, in certain instances, the locally available clay bricks can be weaker than the mortar used in the masonry construction. Therefore, this work aims to numerically simulate the weak brick and strong mortar masonry wall under in-plane shear loading. The discrete element method (DEM) framework is used for numerical simulation in 3DEC software. A simplified micro-modelling strategy is followed with smeared semi-rigid blocks and interfaces, considering the nonlinearities due to expected discontinuities in brick and brick–mortar interface. A coupled tension-shear and compression-shear contact constitutive model simulates the interaction between adjacent smeared brick–mortar blocks and within the smeared brick unit. The DEM framework is validated against the experimental observations available in the literature. The results indicate tensile failure at the interface, which can be attributed to a lower tensile strength of the brick unit and bond at the interface than shear strength. Further, a vertical crack pattern along the interface between smeared brick units and course detachment at the top and bottom corners is observed. The observed failure differs from the typically observed failure patterns in masonry with strong brick and weak mortar.

Concrete-FRP interface plays a critical role in transferring the applied load from the core concrete to fiber in rehabilitated concrete structures. Impregnation of an interfacial defect in the form of void or any anomaly during rehabilitation and/or service life will restrict the retrofitted structure to gain its target strength and eventually will lead to premature failure. The qualitative and quantitative identification of the interfacial void was accomplished satisfactorily in this work. The void identification problem was framed as an optimization-based inverse problem with the purpose of reducing the disparity in the constitutive relation caused by two incompatible stress and strain fields. The disparity originates from the application of two dissimilar constraints in the generation of the stress and strain field. The structural response which facilitates the generation of a kinematically admissible strain field was the surface measurement of the external reinforcement (FRP). The quantitative measure of the interfacial void was parameterized as the damage index in terms of stiffness degradation of the concrete-FRP bond. Numerical validation followed by interfacial characterization with experimental measurement was conducted successfully in this investigation. Detection of the interfacial void in the concrete-FRP interface along with the extent of stiffness degradation quantified as damage index was accomplished in this paper.

The impact mechanical characteristics of concrete specimens are examined using a 76 mm diameter split Hopkinson pressure bar (SHPB) device. In lieu of valid SHPB experiments on concrete material, specimens must be loaded with a specific smooth and trapezoidal incident pulse. This incident waveform type can be produced by utilizing the suitable pulse waveform of the incident pulse. The copper pulse shaper is proposed in the present work to get dynamic equilibrium in the specimen. The influence of pulse shaper sizes on the incident pulses is studied, and suitable pulse shapers are found for large-diameter SHPB setups. According to the results, if a appropriate pulse shaper is not selected for SHPB experiment, it will affect test results. The high strain rate properties of concrete are investigated in this regard using an appropriate pulse shaper.

Progressive Collapse is a phenomenon when a structural failure of a key component leads to the collapse of the entire structure. This can occur when the structure experiences unexpected loads that it was not designed to handle. To evaluate the potential for progressive collapse, a study was conducted on a 9-storey steel building using the U.S. General Services Administration (GSA) 2016 guidelines. The study evaluated the potential for progressive collapse under three scenarios of the removal of columns and/or bracing from the ground floor. Linear static, Non-linear static, and Non-linear Dynamic analysis were performed using ETABS software. Buckling Restrained Braces were used to evaluate the progressive collapse potential of steel-braced buildings. Buckling Restrained Brace has the same behavior in both tension as well as compression. Chevron Bracing (INV-V), 2 Story X Bracing (2XBF), and V Bracing are considered for the present study. Six different Bracing location is considered for this study. As a result of the linear static procedure, the Demand Capacity Ratio (DCR) was computed for structural components such as beams, columns, and bracing. A Load–Displacement plot was generated from the results of the nonlinear static analysis. By introducing Buckling Restrained Brace (BRB) systems in multistory steel buildings, the study found that the structures’ resilience against progressive collapse can be significantly improved.

The present study analyses the flexural buckling behavior of the composite laminated I beam using the classical lamination theory by developing a general analytical model subjected to vertical loading with simply supported and cantilever support conditions using MATLAB. The buckling analysis and flexural responses were studied for arbitrary symmetric and unsymmetrical laminate sequence configuration. The governing equations are derived from the total potential energy theory. Numerical results for deflection and critical buckling load are obtained for thin-walled composites I section beam under vertical loading for varying stacking sequences and support conditions were presented. Later the PSO optimization technique was used for optimizing the results obtained and the code developed was validated. It was observed that the results obtained by the present method and MATLAB code shows good agreement with the previous available results. The maximum deflection for composite beam for simply supported cases for [90/−90] orientation and minimum deflection for [0/−0] orientation ply angle composite beam. The maximum buckling load for composite beam for simply supported beam cases was obtained for unidirectional fiber angle laminate composite beams.

Masonry structures cover a very wide range of monumental works in space and time, covering almost 6000 years. The structural assessment of the load-carrying capacity of such old structures depends on several parameters such as: (a) material strength; (b) texture of the structure; (c) geometrical form and dimensions; (d) existing loading and constraints; and (e) expected loadings at failure. Detailed calculations are also required for the structural evaluation using most of the above parameters firstly by considering the gravity loads and secondly by the combination of gravity load and lateral action in areas of high seismicity. However, at the same time, it is equally significant for the structural engineer, who is involved in structural restoration design, to know in depth qualitatively the basic forms and their structural behaviour of monumental buildings. The structural engineer in charge must understand from the beginning, qualitatively, the structural behaviour of a building under consideration to various basic actions so that one can make a preliminary diagnosis of the causes that are responsible for the existing damages (cracks, drifts, settlements, splitting etc.). In this way, one will be in a position to focus on the detailed research, in situ and laboratory, to the critical points of the building, and can conduct the analysis and design using suitable models for a credible safety evaluation. Therefore, an effort is made in the present study to give a qualitative approach to the structural behaviour of the basic structural forms of masonry monumental and historical buildings, where the consequences of the seismic action are traumatic now and then. This article gives an outline and creates background information for further structural evaluation of the monuments.

Recent studies in-slab systems show possibilities for advancement in the conventional techniques of slab casting. Contemporary developments in the field of design of RCC slabs are associated with Flat and Grid slabs. Flat Slabs are highly advantageous in construction, as they provide minimum depth, less material, speedy construction and tolerate non-uniform column grids. The flat slab rests directly on the column, and the thick beams which are present in the conventional slabs get fused in the flat slab only. Drop panels or column heads are used in case of heavy loads to resist shear failures. Flat slabs are convenient for fire and acoustics treatments and also provide aesthetical flexibility. Grid or waffle slabs have closely spaced beams perpendicular to each other at regular intervals with the slab resting on them. As they provide greater spans, they are generally used for large rooms such as auditoriums, theatre halls, malls etc. This paper focuses on the economic comparison of the conventional, flat, and grid slabs separately. For the above objective, buildings with varying numbers of storeys and different slabs are analysed.

Concrete-Filled Steel Tube (CFST) columns have gained prominence in past two decades. But it is observed that, majority of the research work was concentrated on the stub CFST column. When the length of the column increases, failure of column changes from crushing to global buckling, hence it is required to study the effect of length on the strength of the CFST column. The main aim of the current paper is to investigate the effect of varying length on strength of slender CFST columns with varying confinement effect for the combination of high strength and normal strength material grades of steel and concrete. A finite element (FE) based study is performed on 48 slender CFST columns having length to external diameter (L/D) ratio of 10 and 20. CFST columns of diameter (D) of 250 mm and 350 mm with diameter to tube thickness (D/t) ratio of 25 and 40 are used for study. Concrete grades C30/37, C60/75 and steel grades S235, S550, S690 are used to study the effect of combinations of normal and high strength materials on strength of slender CFST columns. Standard hinge-roller boundary condition is considered for all FE analysis. Linear buckling analysis is performed to obtain the buckling modes of the CFST columns which then is used for perturbrating the geometry for performing the nonlinear buckling analysis to achieve the global failure mechanism. Column strength, load-deformation curves, deformation pattern and effect of confinement under varying length is evaluated. Strength of CFST columns obtained from the FE analysis is compared with the code predicted strength from EN 1994-1-1:2004 (EC4) and ANSI/AISC 360-05(AISC) provisions to examine their suitability for above considered geometric and material parameters.

Operational modal analysis (OMA) has attracted a lot of interest in the field of civil engineering during the past 15 years, to monitor structural health of large-scale infrastructure. Traditional contact-based modal analysis techniques require physically attached sensors for data collection and vibration-based monitoring which can impose mass-loading as well as financial constraints upon installation and maintenance of such devices. Recently, non-contact video-based modal analysis methods for structures with arbitrary complexity using advanced computer vision techniques such as video motion magnification and optical flow have gained much importance. However, these techniques require prior information about the natural frequency ranges of the structure and utilize steerable pyramids which are complex multi-scale image decomposition filters. To address these issues, a technique is suggested in this study to extract the modal parameters (modal frequencies and mode shapes) blindly from the recorded structural vibration video signal using an unsupervised machine learning algorithm called Non-Negative Matrix Factorization (NNMF) integrated with a blind source separation technique called Generalized Complexity Pursuit (GCP). NNMF algorithm can be directly applied to the raw pixel-time series formed from the video data to obtain the temporal components, which can be demixed using GCP to identify the individual modal frequencies and mode shapes. The above algorithm is first validated on an 8-degree of freedom (DOF) numerical model and then implemented on laboratory-scale models (multi-storey shear frame model) as well as on real-world recorded structural vibration video like the Tacoma Narrows bridge to determine its noise sensitivity. The modal parameters extracted are compared with those from available literature for validation. The estimation errors obtained from all the validations are well below 1%, which makes the technique quite suitable and reliable for structural vibration monitoring, in identifying and reproducing even close-spaced as well as mildly excited modes of vibration.

Buildings in seismic areas are being vulnerable to strong ground accelerations during the times of ground shaking, which results in the occurrence of severe base shear and acceleration in the structure. As a remedy, passive devices (Base Isolators) were introduced to diminish the seismic energy transferred to the building but the isolators are found to be severally damaged during the near fault seismic excitations and are also exposed to large displacements. Therefore, after the post-earthquake the isolator’s working conditions becomes critical. Hence to overcome those limitations a novel passive device named “Negative Stiffness Device (NSD)” has been introduce to impart apparent weakening the structure at the level of deployment of the device. A Pre-compressed spring, pivot plate, lever arm, two chevron braces and gap spring assembly are the components of the device. In the current study a G + 3 Reinforced Concrete (R.C) frame bare building which is situated in zone-III has been considered for the analysis and a Non-Linear Time History Analysis has been carried out to access the seismic response reduction of the structure with the implementation of NSD at various storey heights. From the results observed, the NSD is found to be efficient in mitigating the structure’s earthquake responses. The building’s base shear and acceleration are diminished about (30–45) % and (15–30) % respectively.