Recent Developments in Structural Engineering, Volume 1

Smoothed particle hydrodynamics (SPH) is a powerful tool for modelling industrial situations with massive deformations. One downside of the SPH approach is its high CPU cost when compared to traditional finite elements. To undertake a parametric analysis of CLSH (Smoothening length constant) and “Hmax” (Maximum smoothening length), a pre-validated FE Lagrangian model of high velocity projectile impact is chosen. The retardation of projectile velocity and kinetic energy, deformation of projectile, crack propagation in ceramic, and computational resources are chosen as the standards of comparison between the finite element Lagrangian model and a set of SPH models with different parameters.

In the present study a case study is discussed incorporating the retrofitting techniques primarily in the form of reinforced concrete (RC) jacketing to enhance the structural stability and strength of civil engineering structures damaged under violent forces generated by the blast vibrations. Finite element approach is adopted to analysis and design the structure with finite element software ETABS. The case study considers an existing five storey reinforced concrete building located in the vicinity of frequent mining activities making the structure vulnerable to blast induced damages. The structure is designed considering the conventional loadings namely dead loads, live loads, and seismic loads along with the seismic load combinations. The study explores the performance of a seismically safe building subjected to underground blast induced vibrations. The objective and novelty of the study is to evaluate the deficit demand of the structure against the blast induced in terms of flexural and shear demand of the existing structure. The study compares the structural performance of the building in terms of shear force and bending moment under seismic and blast loadings. The study suggests retrofitting the failed members with RC jacketing to avoid such failures. Retrofitting the structure resulted in the reduction of displacement values by 31% when subjected to blast induced vibrations when compared with without retrofitting structure. The demand capacity ratio is also evaluated for with and without retrofitting condition and it is observed that retrofitting technique is an excellent method in improving the performance of the building damaged due to blast vibration.

One of the most promising materials for concrete buildings is ultra-high-performance concrete (UHPC). Traditional UHPC compositions include significant amounts of cement, silica fume, superplasticizer, and other pricey and carbon-intensive ingredients. In order to develop a more cost-effective and environmentally friendly UHPC using alternative UHPC dosages that utilise locally accessible resources, it is necessary to study the relationships between the UHPC dosage and its resulting properties. This study employs two novel machine learning algorithms, the AdaBoost regressor and K-nearest neighbor, to illustrate the non-linear relationships between dose mixture design and the compressive strength of UHPC. A dataset comprising 810 UHPC mixture collections with 15 input variables, namely cement, slag, fly ash, silica fume, quartz powder, limestone powder, nano silica, water, coarse aggregate, fine aggregate, fibre, superplasticizer, relative humidity, temperature, and age has been used to train the models. After adjusting the regression model, the prediction performance of the two models is comprehensively compared using different performance parameters. The proposed AdaBoost regressor model achieved the most precise prediction during the testing phase, outperforming the K-nearest neighbor regressor, as evident from the statistical results and Taylor diagram. Shapley additive explanations (SHAP) measure feature significance and variable influence on a prediction. The SHAP interpretations matched the typical compressive behaviour of concrete, confirming the typical relationship between machine learning predictions and actual events. The proposed AdaBoost model can be used as a high-performance tool to estimate the compressive strength of ultra-high performance concrete during the design and construction phases of civil engineering projects based on the experimental results.

Liquid retaining tank probably the only structure where liquid mass is considered as modal masses i.e., convective, in which portion of the liquid sloshes on the top and the impulsive which moves along with the tank body. Various researchers made investigations on seismic analysis of liquid storage tanks by including two distinct modes. Based on the different outcomes of their research, various codes like API 650, NZSEE etc. have set the procedures to compute different quantities like time periods, base shears, base moments, hydrodynamic pressures with respect to the two modes. Present paper deals with parametric and comparative study of such quantities with the different tanks as per the API 650 and NZSEE guidelines. Also, study of tank seismic parameters of design spectra of both the types of modes is discussed. The purpose of the study is to get overall idea of the weightage of each mode (Convective and sloshing) in view of analysis part of the tanks. Further, some of the identified tank damages believed to occurred because of the convective mass also been discussed. Authors have observed that the percentage of convective mass contribution in different quantities is very less. So, the analysis of the tanks can be made curtailed by merging the convective mass to the impulsive and thus single mode analysis can be adopted at great extent at least in the seismically less prone zones. In addition of the above, the design spectrum can further be reduced to the single coefficient value on higher side if single merged impulsive mode is adopted in the analysis. It is to note, literature survey clears that investigation on analysis with shell flexibility, out of roundness and soil structure interaction not affecting the convective mass anymore. The observations discussed in the paper may helpful to structural designer for making simplified i.e. single merged mass mode analysis for the design of tanks. Authors’ view is thus inclined towards consideration of merged impulsive/single mass along with shell flexibility for finding more precise structural properties like time period, base shear, base moment or in any analytical study will be authentic in the tank analysis.

Thin cylindrical shells have wide applications owing to its large specific bending stiffness as well as very light weight design. Buckling of shells in the elastic regime is a critical consideration in design. The Knock Down Factors (KDFs) are specified for designing against the significant disparity between the analytical (linearized) critical load with the experimental, obtained as a product of the linearized critical load and the KDFs. The closely spaced buckling modes undergoes nonlinear interactions amongst themselves which is the main reason behind such reductions. In addition, it is also triggered by the presence of inherent imperfections. However, the KDFs are largely over-conservative, as they are estimated as the lower bounds of the experimental data set. These margins can be narrowed down by non-linear analysis, accounting for the random imperfections. Hence, the present study re-evaluates the KDFs to achieve a target reliability through RBDO. The prohibitively exhaustive computations in RBDO are by passed by proposing a Power law Meta-Model akin to the Koiter’s law of imperfection sensitivity. The power law meta-model is in contrast to the conventional polynomial meta-models often employed in reliability analysis. Further, the stochastic sensitivity of the KDFs (w.r.t the design variables) are equated for optimality and simplifications. The proposed approach is shown to offer significant accuracy and computational efficiency, as demonstrated on a thin cylindrical shell with random imperfections, modelled by a zero-mean, Stationary, Gaussian Stochastic field with appropriate auto-correlations. The static Riks method is conveniently used for the nonlinear finite element (FE) analysis of the shell buckling/post-buckling employing the commercial code ABAQUS. The permissible imperfections for obtaining a particular reliability index using a specific KDF are presented, which may be useful for probabilistic quality control in the construction/fabrication of cylindrical shells.

Seismic Soil-Structure Interaction (SSSI) plays an important role in estimating the long-term performance of the buildings. Seismic demand of building supported over rigid strata are well assessed. Nevertheless, the impact of incorporating embedment depth of shallow foundation on seismic response of the building remains a relatively unexplored area. This ongoing study delves into the effects of varying embedment depths for isolated and raft foundations on the behavior of the building during seismic events. A 10-storey physical model, and isolated, and raft foundation of embedment depth (75, 150, 300 mm) has been used in this study. All the tests are performed using shaking table in laminar container, and verified using numerical investigation. The models are subjected to sine sweep tests (to estimate the natural frequency), and scaled down earthquake motions. Different parameters such as, inter-storey drift, and rocking of foundation has been investigated and reported here. The comparative study brings out the performance of two foundation systems of the building during seismic disturbances. Results indicated that the structure resting on raft foundation with different depth of embedment experiences lesser inter-storey drift (17.73–18.36%), and rocking (9.07–10.64%), in comparison to the structure supported on isolated footing.

This study investigates the structural response of two different concrete structural shapes, rectangular and apsidal, under blast loading. Spherical charges of an emulsion explosive of three different charge weights are considered at seven distinct standoff distances for this parametric study, and the finite element analysis is carried out using the general purpose finite element code LS-DYNA. Forty two simulation runs were carried out. The displacement at a specific node is evaluated for the two structural units, and the results are analysed. The rectangular unit undergoes higher displacements compared to the apsidal unit for all the scenarios considered in the study. Considering the mean values, the peak displacements of the rectangular unit are higher by 390% than the corresponding values for the apsidal unit. The apsidal unit performs better in resisting the explosive loads considered in the study, indicating a better response towards blast resistance.

Numerical simulations were carried out to validate computational and constitutive models against experimental data by conducting ballistic evaluations on plain concrete slabs with an un-confined compressive strength of 48 MPa. Ogival-nose-shaped hard steel projectiles weighing 0.5 and 1 kg were used to impact square plain concrete slabs measuring 450 by 450 mm, with varying thicknesses of 60, 80, and 100 mm. The plain concrete material was modeled using the MAT-111_Holmquist Johnson–Cook (HJC) constitutive material model. The study extensively examined the damage characteristics of concrete and sought to establish correlations with experimental findings. The outcomes revealed that the residual velocities obtained through numerical simulations closely matched the experimental results. However, a notable deviation was observed in terms of the damage assessment, particularly concerning the equivalent diameter of spalling and scabbing of the concrete target. This deviation could be attributed to the absence of the third invariant or lode angle in the yield strength surface, as well as the absence of tensile softening damage in the HJC model. The primary objective of this study was to pinpoint any disparities in damage assessment that may arise when employing the original HJC model for numerical simulations within the LS-DYNA finite element code.

Numerical Studies are carried out to study the ballistic resistance of Whipple shields at hypervelocity impact under different shapes of the projectiles. The Whipple shields consist of a bumper plate and rear wall in which both the plates are made of Al-2024-T3 with sizes of 100 × 100 × 1 and 150 × 150 × 2 mm respectively. The material of the projectile is also made with Al-2024-T3. The shape factor (SF) is defined by the L/d ratio, for the symmetrically ellipsoid shape projectile. A 3-dimensional smooth particle hydrodynamic (SPH) model is created in Ls-Dyna and the model is calibrated with the experimental results. Calibration of the SPH model is done by using the Johnson cook (JC) material model for Whipple shields and projectiles material. These calibrated models are used to study the shape effect of ellipsoid shape projectiles. Maximum residual velocity is observed at shape factor 4.46 under high-velocity impact. However, in hypervelocity impact, the ballistic resistance of the Whipple shield decreases with an increase in SF. It is also observed that the residual velocity is minimum for SF = 0.28 for hypervelocity impact.

Graphene, an intriguing material with exceptional properties, has captured considerable interest over the last decade. However, the specific role of graphene in modified cementitious materials has yet to be comprehensively elucidated existing literature. In recent years, graphene has been used widely in cementitious material due to its distinctive 2D structure, surface morphology and exceptional mechanical properties. The incorporation of graphene, even at very low concentrations, has significantly enhanced the overall mechanical properties of cementitious material, such as compressive, tensile, flexural, and bond strength. In addition, it offers an impermeable layer that effectively inhibits the corrosion of reinforcing rebars. This extensive literature review aims to explore the fundamental aspects and applications of graphene, offering valuable insights into the influence of graphene on the mechanical and durability properties of cementitious materials. Thus, the present study aims to contribute to the existing understanding of the effects of graphene on cementitious materials, paving the way for the further advancements.

Particulate polymer composites (PPC) are widely used in various engineering fields for their high strength-to-weight ratio and impressive mechanical properties. Typically, methods for predicting the mechanical behavior of such materials include tensile tests, finite element simulations, and numerical analysis. However, recent advances in artificial intelligence (AI) have enabled improved prediction of mechanical behavior of various materials. In AI-based approaches, microstructural information like fiber orientation and grain morphology are generally defined as inputs through multi-dimensional images. The objective of the proposed investigation is to reduce the prediction complexity and computational efficiency in AI-based methods when compared with finite element modeling (FEM). AI-based algorithms are typically data-driven approaches primarily dependent on the input data quality. Subsequently, the optimal selection of the input labels (material properties using FEM software) is imperative to ensure higher prediction accuracy. In this study, we predict the mechanical behavior of a particulate polymer composite based on the images of the stress fields developed from FEM simulations used to train a paired image-to-image translation model (pix2pix). The pix2pix model is based on a conditional Generative Adversarial Network (cGAN), where we train the encoder by 512 × 512 pixel images corresponding to stresses in the y-direction. The results of the AI algorithm show that the pix2pix model is computationally efficient and highly accurate in predicting the effective stress fields of a detailed representative area element of FEM. We observed the maximum accuracy determined by the correlation coefficient as 0.906 at 20,000 iterations of the algorithm.

Vibration control efficiency of shape memory alloy (SMA) assisted friction pendulum (SMA-FP) for building during blast induced ground motion (BIGM) has been explore here, and compared with the performance of conventional friction pendulum (FP) isolation system. This study analyzes the structural behavior of a five-storey steel shear building subjected to blast loading. To this end, nonlinear time-history analyses (NLTHA) are performed to evaluate the responses of the linear shear building structure isolated with the nonlinear base isolation (BI) system (either FP or SMA-FP). Study results shows that, the conventional FP BI system loses is peak floor acceleration control efficiency and shows large peak isolator displacement with noticeable residual displacement. Opposing to this, presence of SMA not only improves the isolator displacement and residual displacements, slightly reduces the peak floor acceleration. Furthermore, the study result reveals that, a particular combination of friction coefficient and SMA wire strength maximizes the isolator control efficiency i.e. minimizes the top floor peak acceleration. Such optimally designed SMA-FP isolator offers 3% higher top floor peak acceleration efficiency than FP isolator, whereas substantially reduces peak and residual isolator displacement by 37% and 6%, respectively. Finally, the enhanced control efficiency of SMA-FP BI over FP BI under the BIGM has been demonstrated through parametrical study, taking an inclusive range of building, isolators, and BIGM parameters.

Dynamic response of plates subjected to blast loading is important in the design of protective structures. Among different types of metallic and polymeric materials, performance evaluation of the plates made from such construction materials helps in selection and design of the most efficient protective structure. As the choice of material for the plates is crucial, affecting the overall blast performance, in this study, dynamic response of plates subjected to successive blast loads is studied and it is compared with the conventional steel plates. The materials of the plates chosen for this study are aluminum and carbon fiber reinforced polymer (CFRP) that are compared with the plates made of steel when exposed to series of blast events. Further, residual strength of the plates after successive blast loads has been evaluated by conducting a detailed finite element (FE) based investigation considering damage in the plates. It is observed that the choice of construction material for the plates plays a significant role in the blast response. Unsurprisingly, the varied plate thickness to achieve the same performance level, helped in achieving comparable performance, albeit with changed self-weight of the plates. Hence, for maximizing blast response while minimizing self-weight of the plate, series of parametric studies are conducted to arrive at the most efficient design of the plate subjected to successive blast loads.

Steel buildings are getting popular because of their transportability, reusability and long life due to their maintainability. Earthquakes cause significant damage to the buildings. The extent of this damage is directly proportional to Inter-Storey Drift (ISD). Concentric Braced Frames (CBF) and Eccentric Braced Frames (EBF) are two commonly used braced frame systems that limit the ISD by increasing the building’s lateral stiffness. This study is divided into two segments. The 1st section presents an overview of existing literature on EBF, with a primary focus on works that demonstrate EBF’s superiority over CBF. This section delves into matters related to EBF, such as energy dissipation through ductile link behavior and the potential for substantial floor deflection. In 2nd part, the performance of CBF and EBF is compared in relation to ISD and energy dissipation. Four steel buildings with chevron (inverted V) braces [one each for CBF, EBF0.4 (link length 0.4 m), EBF0.6 (link length 0.6 m), and EBF0.8 (link length 0.8 m)] have been modelled in SAP 2000 and designed as per the guidelines of IS 800 2007 and IS 1893 2016, keeping design base shear constant in all four models. Non-linear Time history analysis (NLTHA) is executed to conduct a comparative assessment of ISD in all the above models. The comparison of energy dissipation is based on the total strain energy capacity of CBF braces and EBF links. From this study, CBF are found to be performing much better than EBF.

Analysis of suspension bridges involves a lot of skills, and sometimes it is difficult to predict the behavior using computer software due to its geometrical complexity. The study of suspension bridges consists of calculating initial element forces due to dead loads based on which the initial geometric stiffness is modified. Further, the live load analysis is done by superimposing its effects. Geometric stiffness is the most fundamental aspect of the structural behavior of suspension bridges. This study is focused on creating a step-wise framework and a tool to reduce the analysis effort required for the analysis of suspension bridges. This work involves the development of a finite element program using ‘python’ language for the study of classical suspension bridges (SB) and suspension bridges with stability cables (SBSC). The developed program is applied over multiple steps to modify the initial stiffness of the cable elements; the analysis results are verified using the deflection theory. Further, the dimensionless charts for deflection and bending moments are produced so that they are usable for any span and structural properties, which will not only support the bridge designer for preliminary analysis but also helps as an effective tool to verify their results calculated by modern computer software on the basis of taken assumptions.

Structure health monitoring (SHM) is essential for monitoring damage in dynamic systems. It helps in the early detection of damage which, prevent any economic and life loss ensuring the safety of the system. In this work, we are interested in damage detection for dynamic problems having noisy data. The noisy data may be collected from sensors. It is always difficult to deal with noisy data when there is damage in a dynamic system as it is a high-dimensional problem. For that reason, the proper orthogonal decomposition (POD) has been used to reduce dimensionality. As a result, it was possible to represent a dynamic problem by a very low number of POD modes. Furthermore, the governing differential equations were represented using the state space model, and the Bayesian filtering approach was used to predict the responses and parameters. The developed model was first fitted by the noisy data on the reduced space, and the model parameters were found. Thereafter, Bayesian filtering was used for the prediction of responses and system parameters (i.e. stiffness) for a dynamic problem. Often, for a dynamic problem, the data is updated continuously. To take into account the case, the main idea of the developed model was to predict the stiffness in an online manner, such that it can predict the real-time behaviour of the stiffness, and the damage can be measured in the online mode as well. The developed model was applied to a muti-degrees of freedom dynamical system with synthetic data for validation. It was found that the developed approach can predict the evolution of the response and stiffness quite accurately and efficiently.

In recent construction, buckling restrained braces (BRBs) have grown in prominence as seismic devices. One of the most worrying aspects of the design of these braces is the choice of the core cross-section of BRBs. In order to identify the most effective and practical BRB cross-section, nine different BRBs with various core cross-section configurations are investigated for hysteretic behavior and energy dissipation capacity using non-linear finite element analysis. Maximum energy dissipation was recorded for a rectangular core cross-section along the yield length with cruciform end parts and hollow circular BRBs. Additionally, all-steel BRBs behaved more hysterically than those BRBs loaded with concrete.

In the Indian Himalayan region, a centuries old traditional vernacular construction and architecture method, known as Kath-kuni (also called: ‘cator-and-cribbage’ or ‘timber laced masonry’), well-known as a building style which is seismic resistant. This construction methodology is never conventionally engineered and it is essential to know about their performance under gravitational and seismic conditions. In this study experimental investigations were carried out on a scaled down wall model, built and tested at Indian Institute of Technology Roorkee. For the model, stones were replaced with the concrete bricks of M30 and deodar wood was used for wooden beams and joints. To this end, research, in-plane testing of wall to characterise its overall behaviour, deformations of wall and its components, ductility, testing of materials used, have been carried out. The wooden specimens were tested for their mechanical properties. The wall was loaded with an overburden of 0.045 MPa and subsequently a lateral load was applied in displacement increments. The failure of the wall was governed by internal rotation in the wooden layer and wall specimen showed a high ductility. The behaviour factor R of the tested wall is calculated to be 6.24 which comes out to be approximately 2.5 times higher than the values suggested for the regular masonry as per IS 1893. Most important seismic capacity features that contributed in ductility were found to be the wooden connections (kadil joints and maanwi joints). Since no adhesive was used in between wooden members they were allowed to rotate once the friction capacity in between wooden and stone layers exceeded.

This study examines the influence of dynamic material strength on the blast response of reinforced concrete (RC) buildings. The structural response of four RC buildings, designed to resist various seismic demands with three different infill strengths, is examined under surface burst using an uncoupled approach. The time-histories of blast-induced loads are imposed directly on the beam-column joints that are exposed. Nonlinear dynamic response history analysis is then performed to acquire different responses. It is observed that the consideration of dynamic material strength results in around a 5.0% reduction in the peak displacement at different floor levels. Nevertheless, the variation of the peak displacement with floor level and with respect to scaled distance ( $$Z),$$ Z ) , as well as the variation of peak interstory drift ratio (IDR) with $$Z$$ Z are similar to that of buildings without considering dynamic material strength. In addition, the effect of infill strength is found to be insignificant on this response reduction. Further, the response reduction due to dynamic material strength is found to be less in buildings designed for lower seismic demand in comparison to those designed for higher seismic demand. Furthermore, probabilistic assessment demonstrated that accounting for uncertainty in blast load parameters such as charge weight and standoff distance plays a significant role in the accurate assessment of blast response as it results in the increase of peak IDR response in buildings with lesser infill strength and lower seismic demands.

Cracks on the concrete surface are one of the early identifications of the structure deterioration, which is important for maintenance and may cause serious environmental harm if left untreated. In addition to detracting from the aesthetics of monolithic construction, cracks in concrete structures may indicate serious structural issues. Such damage can appear as minor or severe cracks that eventually develop and cause the structure to collapse or to be destroyed. Manual visual inspection of cracks is a time-consuming and error-prone process. The crack is invisible during manual visual inspection, which is time-consuming and entirely dependent on the expertise of specialists and experienced inspectors. Hence, automatic image-based crack detection is employed to replace manual inspection. Automated crack detection techniques may significantly reduce the amount of time and money spent on structural health inspection and monitoring. Inaccessible areas of a concrete structure may also be easily maintained using crack detection based on image processing. To determine how well the proposed algorithm performs and how well it overcomes the limitations of the current manual technique, it has been tested against a variety of cracks in concrete structure images. This paper presents an innovative method for detecting cracks in concrete structures using image processing.

Basalt fibres helps to enhance the concrete’s toughened qualities and the use of Basalt fibres has grown recently. The hardened condition of concrete is altered when these fibres are incorporated into it. Yet, these fibres also have an impact on the workability of the corresponding fresh characteristics of concrete. It is crucial to comprehend how the basalt fibres’ integration affects the characteristics of fresh and cured concrete. Basalt fibre is an ideal material to reinforce concrete because of its great strength and heat resistance qualities, strong resilience to an alkaline environment, and low cost. Examining the impact of use of length of basalt fibre and it’s content on various mechanical properties of concrete plays an important role. The fact is that the length of basalt fibre and proportions have an significant impact on these properties. Workability, Strength in Compression, Strength on tension, flexural strength, permeability, and unit weight are among the mechanical characteristics of concrete are tested. The goal of this study is to provide a summary of what is currently known regarding the effects of basalt fibre on the characteristics of concrete. The study includes relevant research and conclusions, as well as the primary investigation and comparison between other available fibres. Current advances in the use of Basalt fibre and different prediction methodologies.

Modal identification describes the behaviour of the structure under dynamic loading conditions such as earthquake, wind, blast (impact), wave, traffic, etc. A newly developed variational mode decomposition (VMD) technique identifies the modal parameters of structure based on dynamic responses. The vibration-based VMD techniques mainly rely on a sensor-driven data collection approach for the response of the structure. To develop an effective modal identification system, a method for determining the optimal number and location of sensors is proposed. The vibration response of an optimised sensor network lowers the installation of sensors and operational costs, simplifies modal identification system computing operations, and provides the modal parameter estimation. The Spline interpolation methodology for optimising the number of sensors and their positions in the building is proposed in this study. A MAC (Modal Assurance Criteria) value between the exact and estimated mode shapes was utilized as a criterion for determining the minimum number of sensors. In this study, the capability of the VMD technique to determine a structure’s modal parameter with the help of a limited number of sensors is demonstrated in the multi-storey building and the UCLA Factor building, and the results show that the proposed VMD approach can easily identify the modal parameter of the building with better accuracy.

Seismic analysis of concrete gravity dams is vital for ensuring their safety and performance during earthquakes. Gravity dams are designed to resist loads due to their weight but the dynamic loads induced during seismic events can cause significant damage. The length of the reservoir could play an important role in the seismic responses of the dam. In this study, the effect of reservoir length on the seismic response of the Baglihar dam is investigated. The study uses finite element models of the dam and dam-reservoir systems to simulate the seismic behavior of the dam for different reservoir lengths, ranging from H to 6H (H: height of the dam). These systems are modeled as two-dimensional structures and the dynamic analysis is carried out using the linear Response History analysis method with three different earthquakes. The results are compared in terms of crest displacement and the principal stresses at the various sections of the dam. In addition, the study examined the effect of the two different properties of the dam material on the seismic response. The study indicated that the relationship between reservoir length and responses is not necessarily linear but depends upon the geometry of the dam and the ground motion. However, after a certain length of the reservoir, the variation in responses becomes less significant. The material properties of the dam also seem to affect the seismic response, as by increasing the stiffness of the dam material the responses can be reduced.

In current scenario, there is no comprehensive utilization for abundance of non-biodegradable tire waste and scrap of tires which affect the environment and whole ecosystem as a Hazardous waste because a small proportion of waste is recycled. As per studies it has been investigated to modify the conventional concrete into crumb rubber concrete, coarse aggregates or fine aggregates can be replaced by 25% of crumb rubber beyond which toughness decreases including modulus of elasticity. In specific scenario, if crumb rubber replacement percentage exceeds 20% by fine aggregates, it increases the adverse effect on concrete properties and 25% replacement of coarse aggregate by crumb rubber reduces 45% strength. This reason is adding rubber to concrete decreases its strength under static load and the ability of rubber to absorb the dynamic energy enhance the performance of concrete under impact loading. In general, the strength and energy absorption capability of crumb rubber concrete was better under impact loading than static loading sequentially dynamic fracture energy is higher than static fracture.

A bridge might sustain significant damage or collapse due to an earthquake’s pounding on nearby, insufficiently separated structures. Knowing the maximum impact force value anticipated during an earthquake is necessary to evaluate the damage’s extent and design various pounding mitigation techniques. Therefore, the present study aims to investigate the parameters affecting the pounding forces of two nearby separated bridge decks, including soil-structure interaction (SSI). Analyses of the results reveal that consideration of the flexibility of the soil supporting the foundation would affect the maximum pounding force value, even if the structural parameters such as gap sizes, masses of the colliding structure, and damping of the colliding decks are considered to the same in both in structural condition, flexible base condition (with SSI) and fixed base condition (without SSI). It is observed from the study that consideration of SSI would reduce the maximum pounding force, which further decreases with an increase in gap size. The study also examines the effect of the mass ratio of colliding bridge decks, and it has been observed that the maximum pounding force increases with an increase in the mass ratio of colliding bridge decks. The study investigates the effect of soil flexibility (SSI) and fixed base (without SSI) on the peak value of pounding force for the different mass ratios of colliding bodies.

Single-angle members are commonly used in various structures due to their ease of assembly. However, designing them as compression members can be challenging due to their asymmetric shape. The design approach for unequal-angle sections in India lacks sufficient study. This paper aims to compare the Indian and Canadian standard design approaches for analyzing single-unequal-angles as compression members with reference to Rankine’s column theory, and investigate their buckling behavior through finite element analysis. Additionally, the feasibility of using double-angle sections as replacements for single-angle sections with equivalent cross-sectional areas is explored. The findings indicate that the Indian standard approach is more optimal than the Canadian standard approach, and the use of double-angle replacements for single angles effectively eliminates torsional effects on buckling. This study contributes to a better understanding of the analysis and design of single-unequal-angle compression members.

Jointed plain concrete pavement (JPCP) are designed using guidelines like PCA (Thickness design for concrete highway and street pavements, Portland Cement Association), and IRC 58 (Guidelines for the design of plain jointed rigid pavements for highways, Indian Road Congress). These guidelines suggest nearly the same slab size (3.5 × 4.5 m) for the construction. It has been observed that shorter panels are often used in construction of concrete pavement in India. Therefore, it is important to study the effect of panel size on the thickness design. It is general understanding that, the thickness requirement of concrete pavement may decrease compared to traditional sized pavement due to reduction in flexural stresses. However, IRC 58 (2015) and PCA (1984) is silent about the design of JPCP for size of panels other than standard. Literature related to design of short panel concrete pavement are studied and important conclusions are drawn. In this study, finite element model (FEM) of a concrete slab is developed using computer software and validated with existing methods. Various short size slab panels are analyzed considering single and tandem axle load. The behavior of these slabs is studied and recommendations are presented.

Currently, the application of nanomaterials in cement concrete structures is become most prominent for enhancing various properties. The rapid demand in urbanization leads to an increase in the development of pre-cast elements for reducing the time and cost of construction. However, the development of pre-cast elements depends upon the formwork removal of concrete, which only possible when cement attains its sufficient strength gain. In this work a synthesis method for the preparation of CSH-based nanomaterial using the chemical process is proposed for early strength development in cementitious composites. The method includes the use of silica from industrial waste and calcium bearing salt for the precipitation of CSH. The synthesized CSH nanomaterial further characterized using scanning electron microscopy (FE-SEM). The presence of CSH hardening accelerator acts as a seeding material in cementitious composites and provides an additional nucleation site thereby accelerates the hydration process and leads an early strength development. The precipitated CSH was used at different dosage in order to investigate the early strength development using heat of hydration, and compressive strength test measurements.

The effects of building height on the seismic vulnerability assessment of reinforced concrete (RC) frame buildings are an important consideration for structural engineers and designers. Since high-rise buildings have become more common in earthquake-prone regions in recent years, this topic has received significant attention because buildings’ dynamic characteristics change with the structure’s height. Several factors affect a building’s seismic vulnerability, such as its height, mass, and structural characteristics. This paper has discussed the various factors that influence the seismic performance of RC-frame buildings, such as the building’s strength and ductility, as well as the effects on the fragility curve due to an increase in the building’s height. Additionally, the paper has discussed the different seismic hazard levels (DBE and MCE) and how they impact the vulnerability of tall buildings. This paper’s findings will help structural engineers and designers understand the effect of building height on the seismic vulnerability assessment of RC-frame buildings, enabling them to design more resilient structures in earthquake-prone regions.

Heritage structures across the globe are degrading because of their age. In India, the Archaeological Survey of India (ASI) recommends preserving heritage structures to safeguard their structural integrity. This study aims to implement You Only Look Once version 8 (YOLOv8), a deep learning (DL) architecture, as a tool to detect and localize surface damages in the form of cracks. As a case study, the Darbhanga Fort, made of brick masonry and located in Darbhanga, Bihar, has been considered. Because of the absence of periodic maintenance, huge vegetation, cracks, and spalling are present. The custom YOLOv8 model has been trained on the dataset containing 4056 cracked images. Performance parameters like mean average precision (mAP), precision, recall, F1-score, and confusion matrix are obtained to check the efficacy of the model. The YOLOv8 model attains a mAP_0.5 of 98.6%, a mAP_0.5:0.95 of 87.9%, a recall of 97.5%, and a precision of 96.6%. The obtained results show that the deployed model is capable of sensing and localizing cracks present in the structure. An open-source crack dataset of the present study along with its bounding box labels has been published on the Mendeley database.

Corrosion of reinforcement bars in a reinforced concrete (RC) structure poses a potential threat to its strength and serviceability under a seismic environment. The severity of corrosion damage is governed primarily by the rate of corrosion and location of corrosion damage in the reinforcement bars. In the present study, the numerical simulation of the seismic behavior of RC Exterior beam-column joints (BCJ) was performed under the effect of non-uniform corrosion. Three non-seismically detailed BCJ specimen models were developed using 3D nonlinear finite element (FE) analysis with the software ABAQUS. The primary input parameters were the diametric reduction of the corrosion-damaged bars, modified mechanical properties of corroded bars, and reduced concrete strength due to splitting cracks and spalling of the concrete cover. The results of the simulation exhibited a significant degradation in the seismic performance with an increase in the level of corrosion. The high corrosion rate leads to a brittle fracture in the reinforcing bars, which may ultimately cause premature failure of the structural member.

In the whole procedure of preservation, conservation, and restoration of monuments and historical buildings, structural restoration is considered an undesirable parameter, since it implies interventions on a large scale that might harm the authenticity of a culturally protected building. However, this type of intervention is an inevitable action, because it pertains to the safety of the building and, most importantly, to the safety of the users. In this respect, authenticity and safety are two concepts contradicting each other, and they are ensured by professionals of different origins and philosophies, namely archaeology & architecture on one side and science & technology on the other. In the case of structural restoration, these professionals are required to find a common space of co-existence so that the results of restoration satisfy both concepts, authenticity and safety. The present study gives an overview of thorough knowledge of construction techniques of masonry elements or systems or forms used in the past. In fact, in a period of more than five millennia, various techniques of construction have been developed as a result of big revolutions that have taken place in the history of human civilization. A deep knowledge of all the above is necessary for the suitable selection of present-day techniques and materials that might be used in structural restoration, where principles of reversible or irreversible techniques play a vital role together with the compatibility and durability of intervention materials. The main objective of this study is to guide the structural engineers involved in the structural repair of ancient monuments and buildings of national importance.

Buildings with re-entrant corners evidenced greater vulnerability to past earthquakes due to the diverse movement of building components in different directions. Building codes do not give any requirement for the design of re-entrant corner in buildings rather than placing an upper limit of allowable projection ratio. It is either based on: (i) area of projection of 5 or 30% (e.g., Eurocode and Venezuela) or (ii) length of projection varying from 15 to 40% (e.g., India, Turkey, Iran, Venezuela, etc.). This study aims to delve into the impact of projection area on the performance of 5-storey H, T, and L-shaped buildings (having almost same plan area) by varying the projection area ratios (6.25%, 9.09%, and 12.50%). The design process adheres to the standards of IS 456, IS 1893(1), and IS 13920 for analysis, design, and detailing. Elastic behaviour is studied using modal and response spectrum analyses; inelastic behaviour is studied using nonlinear static and dynamic analyses considering maximum considered earthquake. Confining the projection ratio solely based on projection length may not be sufficient when dealing with buildings featuring re-entrant corners. Thus, all the building code provisions should also limit the projection in buildings with respect to the projection area like Eurocode.

The widespread use of high-density polyethylene (HDPE) plastic products potentially leads to numerous environmental concerns. As a result, it is essential to identify techniques to recycle these wastes without posing environmental risks. The effect of adding waste HDPE flakes on the behavior and characterization of subgrade soil for pavement applications is investigated in this study. Geotechnical laboratory tests, including proctor compaction, California Bearing Ratio (CBR), and unconfined compressive strength (UCS) were carried out to assess the effectiveness of the stabilization with HDPE flakes (1, 3, and 5% by weight of soil). Laboratory investigations showed that the UCS and CBR values of subgrade soil were greatly improved by adding HDPE. The optimum replacement was found to be 5% by weight of soil, and the improvements in proctor compaction, CBR, UCS, and pavement thickness were estimated to be 18.46%, 51.21%, 24%, and 10.82%, respectively. Using the CBR values of the subgrade, the design of flexible pavement has been attempted using the IRC 37:2018 specifications and IITPAVE tool to determine the improvement in the structural behavior of the reinforced pavement section. For simplicity, the linear elastic behavior has been simulated for the bituminous layers, cemented base, granular sub-base, and subgrade layers. The results of the IITPAVE analysis demonstrated that HDPE could be an effective reinforcement for the subgrade layer in road construction. For an increase in HDPE content, the surface deflection and maximum vertical strain were reduced compared to the unreinforced subgrade layer.

Reinforced Concrete (RC) structures are known for their durability and capability of surviving a variety of adverse environmental conditions. However, due to external factors and operational conditions, hidden damage can grow that may eventually lead to gradual/sudden structural failure. Continuous sensor-based health monitoring of such structures will help in increasing their design life. The acoustic emission (AE) technique is one of the potential non-destructive sensor-based continuous structural health monitoring techniques, which helps in detecting the damage in real-time. AE sensors can receive acoustic emission signals, created by internal damage, which can be analyzed in the time–frequency domain through wavelet transform (WT). From the wavelet coefficients, the measure of disorder in a physical system, which is called entropy may be quantitatively described through the concept of Shannon Entropy. In the present study, an attempt has been made to use the Shannon Entropy, Entropy-Frequency curve, and cumulative entropy value to find the damage in an RC slab, where the damage has been simulated using the concept of pencil lead break (PLB). The study indicates that the Entropy-Frequency curve and cumulative entropy value can be utilized to find the damage location at different distances from the sensor location.

In this study, the lateral torsional buckling (LTB) of a partially concrete-encased steel I beam (PCEB) is investigated numerically, and the buckling curve for laterally unrestrained PCEB is found. The concrete encasement improves the beam resistance against LTB, which benefits a steel I beam under construction. A few experimental studies on the LTB of PCEB are found in the literature. However, more studies are needed to understand PCEB behaviour comprehensively, and experiments will become expensive. Therefore, numerical studies are conducted to investigate the post-buckling behaviour of a simply supported laterally unrestrained PCEB. The torsional and warping stiffness of the PCEB is higher than the bare I steel beam, which is evident from enhanced moment capacity. In PCEB, unlike bare steel sections, thinner flanges and webs are more efficient in LTB resistance. LTB is not found in PCEB for a large slenderness range as the concrete encasement makes PCEB behave like a closed cross-section. No moment reduction due to LTB is found for non-dimensional slenderness ratios less than 0.55, whereas for bare steel I beam, this value is about 0.4. Hence, the partial concrete-encasement can shift the steel I beam’s failure mode from elastic member buckling to cross-sectional yielding.

Numerous variables affect the production of Geopolymer, a new-generation material. Therefore, Geopolymer with desirable qualities must be produced with substantial effort and resources. Hence, Taguchi's L9 arrays are adopted in the current study to optimize the selected design parameters in achieving the greatest strength with the least number of trials and time. The study examined four contributing elements at three distinct levels: the molarity of sodium hydroxide, the quantity of ground granulated blast furnace slag, the alkaline solution to binder ratio, and the ratio of sodium silicate to sodium hydroxide solution. Trials 3, 6, and 9 had the greatest strengths of 65.71 MPa, 62.11 MPa, and 60.7 MPa, respectively, with a standard component of 75% slag content. The data were further analyzed using the response indices approach. The percentage of slag was the primary strength-determining criterion, followed by the molarity of sodium hydroxide, alkaline to binder ratio, and, ultimately, the ratio of sodium silicate to sodium hydroxide solution. The current work not only aids in developing a geopolymer mix design that maximizes strength but also assists in understanding the influence of design factors on strength.

Stagnation of storm water on the pavement surfaces poses severe challenges on the urban road transportation system. Pervious concrete is an innovative solution for preventing ponding of water by allowing the water permeation through its structure. Production of pervious concrete equivalent to conventional M20 grade concrete typically demands higher cement content. In order to reduce the consumption of cement, a novel ambient curing based alkali activated pervious concrete was developed with copper slag as fine aggregate with its content ranging from 0 to 20% at 5% intervals. The developed pervious concrete mixes with different percentage of copper slag were tested for determining the mechanical properties. Test results revealed the reduction of porosity with the increase in dosage of copper slag whereas the mechanical properties were observed to have considerable increments.

Tension Leg Platforms (TLPs) compliant in nature are used for deep-water exploration and production. The oceanic environment reduces the serviceability and productivity of the platform. Conventional TMDs are extensively used to mitigate unnecessary vibrations of TLPs under waves, wind, and currents. A properly designed tuned mass damper (TMD) with a larger mass ratio can diminish the response of such structures effectively. However, the inclusion of a substantial auxiliary mass to a TLP increases the cost and may not be feasible in some cases. To navigate this challenge, present study is attempted to convert a portion of the existing mass of a TLP into a tuned mass by using the column-in-column (CIC) concept. For Tension Leg Platforms (TLPs), the platform's deck relies on support from pontoons and columns. These elements are interconnected with the seabed through a taut-mooring system. The columns and pontoons play a crucial role in providing a substantial submerged volume while minimizing overall weight. Utilizing the CIC concept, each column of TLP is divided into two columns. The inner column is connected with the outer column by spring and dashpot having optimum stiffness and damping ratio so that the system works like a TMD system. The usefulness of the anticipated CIC system in response mitigation of TLP under extreme sea state is elucidated numerically. The outcomes of the numerical investigation, on the whole, suggest that the CIC has the potential to effectively alleviate the unfavourable wave-induced response of TLPs.

A connection with an extended shear tab (EST) must withstand both the shear and the moment transmitted from the supported beam. EST connection is widely used in beam-to-column flange and beam-to-girder web arrangements and it has shown to be both inexpensive and simple to install. The current paper presents Artificial Neural Network (ANN) to predict stress values in component parts of EST connections. The selection of the inputs is an important part of the development of an ANN. Three different input selection techniques, including Trial and Error, Correlation Analysis and Average Mutual Information (AMI) are used to determine the final inputs for the models. Trial and error is an efficient approach of selection of the inputs but its tedious method. Recently, correlation analysis between input variables and outcome variables has been used to choose inputs. However, linear correlation analysis makes it inappropriate for application in present case, as the issue at hand is non-linear. The AMI is a non-linear technique to measure the relationship between two variables. In the present study, inputs are chosen using all three aforementioned techniques and feed-forward ANN models are developed to predict stresses in each components of EST connection. ANN model shows an acceptable performance of correlation coefficient i.e., greater than 0.8 and low error measures i.e., RMSE less than 0.08 and MAE less than 0.07. To support this scatter plots also depicts the same results. The results show that, out of the three techniques, ANNs developed model using the AMI method produces the best outcomes.

Earth represents one of the most ancient construction materials, and it is still proving its importance in developed and developing nations around the globe. This paper attempts to study the properties of locally available soil and its suitability as a construction material. The behavior of steel-reinforced, bamboo-reinforced and un-reinforced cement-stabilized compressed earth block masonry specimens was studied for their compressive strength, in-plane flexural strength, out-of-plane flexural strength and diagonal compressive strength. The comparative structural performance of the dry-stacked-interlocked masonry specimens and mortar-stacked-non-interlocked masonry specimens was also investigated in this study. For all these studies, 45 masonry specimens were cast using compressed hollow earth blocks (CHEB) and interlocked compressed earth blocks (ICEB). These CHEB and ICEB were produced using a manually operated press at 10% cement stabilization in the lab. The results of this study were comparable to good quality burnt clay bricks masonry prism strengths. The effect of the reinforcements on the failure pattern of the specimens was also examined, and it was found that the use of the reinforcements in these specimens increased their load carrying capacity. This research provides valuable insights for eco-conscious architects and engineers interested in utilizing earth as a sustainable construction material.

This work deals with robust design optimization (RDO) of structures when information about the input parameters is not adequate to treat them probabilistically. This case often arises while designing a structure under surface blast loading. Neither the mean, standard deviation, nor the probability distribution function is available for surface blast parameters, like charge weight, stand-off distance, overpressure, duration of the pulse, shock front velocity, drag coefficient, etc. In such cases, the parameters can be treated as interval types, where only the ranges of variations of the uncertain parameters are sufficient to model them in a hyper-ellipsoidal convex domain. Subsequently, a convex programming (CP) approach can be used to optimize the system. This approach works fine for simple deterministic systems where loading is equivalent to static in nature. But, the surface blast is a dynamic impulse type load with significant stochastic characteristics. The time-history of blast loading varies significantly even with the same hazard parameter setup due to the inherent uncertainty associated with blast load modeling. A new dual response surface method (RSM)-based RDO procedure is developed in the present paper. The dual RSM captures the stochastic nature of load time-history which in-turn is used to develop a new formulation of RDO. The effectiveness of the proposed approach is explained using a numerical problem of an RC 20-storied building. The RDO is solved by sequential quadratic programming. The results of RDO are compared with the conventional IS: 4991- 1968 based approach to indicate the need for the present approach.

Efforts to reduce construction-related carbon emissions are driving the search for an environmentally friendly alternative to Portland Cement (PC). Alkali activated concrete (AAC) has grown in prominence over the past few decades as a potential alternative to PC concrete. Among the different binders used in AAC, the obligation of heat-curing is often addressed by replacing the fly ash precursor with ground granulated blast furnace slag (GGBS). However, the necessity to adopt fiber-reinforced AAC (FRAAC) is borne out of the need to compensate for the relatively poor early-age mechanical characteristics of ambient-cured AAC. On the other hand, as new building materials emerge, it is crucial to evaluate their impact on the environment before promoting their widespread implementation. In light of this, the current study focuses on the compressive and flexural strength tests for steel and polypropylene (PP) FRAAC. The fiber dosages w.r.t. AAC volume are varied as of 0.1, 0.2, and 0.3%. Life cycle assessments are performed to compare the environmental impacts of AAC to conventional PC concrete. The findings demonstrate a 13 and 11% enhancement in compressive strength of steel and PP FRAAC respectively, in comparison to plain AAC mix. The life cycle impact assessment reveals that the negative impacts of PC on the ecosystem and human health can be reduced by about 44% and 20% respectively, by adopting AAC as a substitute for PC concrete.

Concrete gravity dams, as an energy generating infrastructure, serve a crucial role in the national economy of a country. With numerous earthquakes occurring across the world, seismic safety of dams becomes one of the highest concerns to the engineering community. Seismic damages of Koyna Dam, India in 1967, Hsingfengkiang Dam, China in 1962 and Sefid-Rud Dam, Iran in 1990 have garnered the consensus of the importance of seismic vulnerability assessment of dams. Consequences of dam failures may be catastrophic in terms of casualties, economic and environmental damages. With increasing levels of seismicity of different regions, several existing dams fail to meet the latest seismic design criteria associated with the newly-defined seismic hazard levels of the dam site. The effect of ageing-induced degradations, lack of routine maintenance and sediment deposition intensify the concern further. Therefore, the primary objective of this research is to develop the numerical model of the dam-foundation-reservoir system and validate the model with respect to the existing experimental results from the literature. Subsequently, an extensive parametric study is conducted to investigate the effects of structural geometry, material properties and ground motion characteristics on the seismic vulnerability of the concrete gravity dams. Furthermore, incremental dynamic analysis approach is adopted to derive the seismic fragility functions of the concrete gravity dams under different damage states. The key findings from this research would enlighten the researchers and practicing engineers about the realistic seismic fragility evaluation of concrete gravity dams to build a safe and resilient society.

The primary focus of this study is on the generation of artificial mainshock-aftershock ground motion for the seismic vulnerability assessment of bridges in the Himalayan region of India. For this purpose, first a collection of ground motion records for mainshocks is chosen based on the seismic activity in the region. A record database of real recorded mainshock-aftershock sequences is compiled, and linear model is developed to establish a relationship among the mainshock and aftershock ground motions. This model is then utilized to select aftershocks for the chosen mainshocks records, creating artificial mainshock-aftershock sequences. For the Himalayan region, a highway bridge is chosen for case-study and a comprehensive FE model is generated. A sequence of non-linear time-history analyses are conducted at different scaled levels of ground motion intensity to develop seismic fragility curves. Results demonstrates that the median fragility estimates for the complete damage state exhibit a 26% reduction when considering mainshock-aftershock sequences compared to only mainshock records.

The problem of moving sequential loads over beams is a classic example of vehicle-bridge interaction. Many analytical, numerical, and experiments have been conducted in order to study the dynamic behavior of bridges. However, the computational cost involved in traditional methods is very high. The primary novelty of this paper lies in the creation of a non-dimensional mode-superposition to anticipate the bridge's peak dynamic responses, coupled with the application of ANN-based Multi Input Multi-Output metamodeling. The bridge is idealized as a Euler–Bernoulli beam of uniform cross-section subjected to sequential moving loads commonly known as High Speed Load model-B (HSLM-B). The pearson’s correlation coefficient indicates that the most influential parameter affecting the dynamic response of beams under moving loads is the interspatial distance between loads, i.e., ε followed by speed parameter η. Additionally, the comparison of the best-fitted surrogate models has been conducted to evaluate their robustness and efficiency. The results demonstrate an accuracy level of less than 10 percent, highlighting the high precision and reliability of the surrogate models.

Although India's road system has significantly improved over the past three to four decades, more attention still has to be paid to connectivity in the nation's rural areas. The Pradhan Mantri Gram Sadak Yojana (PMGSY) was established by the Indian government to build the country's rural interior roads. This Yojana focuses on labor-incentive, low-cost technologies for the long-term growth of traffic network in rural regions of India. Such an investigation is carried out in this study. In the present study strength properties of grouted concrete pavement as rigid pavement material to be used in low traffic regions of India are evaluated. The strength characterization of the grouted concrete is evaluated using Non-destructive test methods such as Ultrasonic Pulse Velocity test (UPV) and Rebound Hammer Test. A total of 6 samples of grouted concrete macadam were tested for UPV and Rebound hammer test for a curing period of 28 and 56 days. Based on UPV and Rebound hammer test it was concluded that 4 out of 6 mixes give most favorable strength properties and can be used as rigid pavement in low traffic regions.

The technology of base isolation is widely adopted as a practical and efficient measure to protect the structure from the devastating affects of earthquake forces. The isolation systems achieve desired performance by decoupling the superstructure from the foundation through energy dissipation and avoiding the dominant frequency of the earthquake by elongating the fundamental period of the structure. Hence, to achieve an effective isolation system design, one needs to account for various performance measures to maintain a balance between multiple conflicting objectives. This paper proposes a novel joint optimization approach to find the optimal isolation system parameters that aims to simultaneously minimize the Maximum Interstorey Drift Ratio (MIDR), top floor acceleration (TFA) and base displacement (BD)s. We have chosen Lead Rubber Bearing (LRB) as the isolation system in the present study which is modeled in OpenSees. A popular multi-objective evolutionary algorithm, more specifically NSGA-II is employed to optimize the objective functions simultaneously; though, any other suitable optimization algorithm can be applied. It has been observed that the optimal parameters found with the proposed joint optimization approach performs well.

Hybrid simulation is a dynamic testing technique for structural systems which are not amenable for testing as a whole in the laboratory. In hybrid simulation, only critical part of structure is tested in the laboratory while the remaining part is modelled using finite element method. The study investigates the application of hybrid simulation method for simulating the seismic response of structures. A numerical framework is developed for conducting real time hybrid simulation using a servo hydraulic actuator. OpenFresco is used as middleware between the experimental substructure and the numerical substructure which is modelled in MATLAB. Illustrative example consists of numerical simulation of hybrid testing on a one bay frame model with nonlinear properties. One column of the frame is considered to be nonlinear and is analyzed in OpenFresco. The results of OpenFresco simulation are validated with pure numerical simulations using Explicit Newmark integration scheme.

This research focuses on the development of a novel auxetic metamaterial with bistable unit cells, aiming to achieve large shape transformations and potential applications in emergency shelters, bridges, space-based photovoltaic arrays, and among many others. Unlike traditional monostable auxetic materials, this design incorporates multi-sectioned fiber-reinforced composite laminates exhibiting bistability, combined with monostable symmetric laminates. The geometric nonlinear finite element analysis is conducted at two hierarchical levels to analyze the metamaterial's behavior. Upon the application of a concentrated load, the lattice exhibits auxetic behavior, with the extent of auxeticity increasing with the number of unit cells in a row. The design parameters such as the dimensions and fiber orientation of the bistable plate, as well as the number of composite laminate layers, influence the auxeticity and load-carrying capacity of the lattice. By tailoring these parameters, the metamaterial can be optimized for lightweight, load-bearing, auxetic, and bistable characteristics. This study contributes to the advancement of metamaterials with tunable properties for various engineering applications.

For the last few years there is a growing interest in research domain of structural health monitoring as a number of structural failure and casualty took place all over the world due to negligence in structural health monitoring. Although a lots of research has been carried out in the field of structural health monitoring, but the researchers are still in search of an effective, easy, economical and reliable technique to identify and quantify real life structural damage. The natural frequency and mode shape extraction of Civil Engineering structures are very important for dynamic analysis of structures and structural damage identification as well as damage quantification. In this paper, an operational modal analysis of a steel cantilever beam has been carried out and natural frequency has been extracted by FRF. The operational modal analysis has been carried out by Single Response Technique. During testing, several groups of input force and output acceleration are measured simultaneously. This signal is converted into a frequency domain known as the Fast Fourier Transform (FFT), resulting in a spectrum of input force and output acceleration. Thereafter the coherence function is used to evaluate the quality of FRF. The accuracy of the extracted natural frequency has been further validated by operational modal analysis as well as by analytical technique using MATLAB platform.

The rapid urbanization process has brought to the forefront the critical issue of wastewater discharge from households, which includes grey, brown, and black water. Traditional sewer systems, particularly precast concrete sewers pose various challenges, such as durability concerns, substantial transportation costs, space requirements, and limited flexibility in terms of form and geometry. In response to these challenges, this study introduces an engineered and durable cross-section for 3D concrete printed sewers, offering on-site deployment with enhanced flexibility in shape and geometry. This research is carried out through several key steps. First, sustainability is prioritized by utilizing recycled concrete aggregates in combination with ground granulated blast furnace slag (GGBFS—a byproduct of steel iron industry) based alkali activation during the printing process. Second, the sewer cross-section is topologically optimized to withstand the pure compression forces it encounters. Third, the design incorporates durability considerations to provide superior protection against sewer crown corrosion. The insights gained from this study will empower sewer designers to create robust, durable sewer systems by employing topologically optimal cross-sections and sustainable design practices. By addressing the pressing issue of wastewater discharge through innovative 3D concrete printing technology and sustainable materials, this research contributes to the development of 2.8 times structurally more efficient and resilient urban infrastructure, benefiting both urban planners and the environment.

Reinforced concrete (RC) structural elements are usually designed for fire exposure by evaluating the fire resistance ratings (FRRs). FRRs are quantified by experimental tests, numerical simulations, and using guidelines available in codes and standards. In the Indian context, IS 456, IS 1642 and NBC (vol 1, part 4) mention guidelines for FRRs for RC structures under fire. These guidelines are based on comprehensive experimental testing on isolated/individual elements subjected to standard fire scenarios. They are prescriptive and typically yield FRRs as a function of clear cover and cross-section dimensions. They do not explicitly account for critical considerations such as load ratio, boundary conditions, material properties, etc. Given the rapidly evolving high-rise building stock in India, the aforementioned limitations need detailed investigation. In this context, the current study develops a finite element (FE) analysis-based FRR quantification framework for RC elements (beams and columns) designed using Indian Codes. The FE analysis is based on structural fire analysis in the OpenSees code using a 1-D beam-column element formulation. An experimental validation study is included to demonstrate the accuracy and efficacy of the FE analysis framework. Comprehensive response history analysis (temperatures and deflection histories) is conducted on the RC elements under fire conditions. Also, parametric studies are performed on the influence of cross-section, load ratio, boundary conditions, and clear cover on FRRs of RC elements. Furthermore, comparison studies on the FE analysis-based FRRs vs. FRRs as per Indian codes are presented.

Steel Structures are prone to damage and even collapse when exposed to fire. The objective of the present paper is to investigate the effect of fire on the structural behaviour of a steel beam assembled in a moment resisting frame (MRF) with welded connection, numerically using commercially available software ABAQUS. Two different fire scenarios were used for analysis. In the first case, the frame was exposed to a localised fire source acting underneath the centre of the beam, and the same resulted in maximum temperature concentrated at the midspan with large temperature gradient along its ends. The second scenario represented uniform temperature throughout the beam span where the temperature in the beam followed the same time–temperature curve experienced at the beam midspan, similar to the previous case. The maximum temperature in the exposed beam was around 700 °C. A thermal analysis followed by mechanical analysis was performed, where the temperature profile from the thermal analysis was given as input in the structural analysis. Based on the study, it was observed that the recovery of the deflection of beam after cooling was negligible for frames exposed to localised fire. However, for uniform temperature exposure, there was significant recovery of the same.

The focus of this paper is to propose a design recommendation for side-plate thickness for apex joint. Nested box section has been used as main member (column and rafter) in the frame. The NTBB section is distinctive as it consists of two G-sections welded together along their edges. A notable feature of the NTBB is its potential for tapering, which leads to material savings. The paper presents a non-linear elastoplastic finite element (FE) model, along with an analysis of 112 distinct finite element models. In the subsequent parametric study, variations in side-plate thickness, pitch, and size were explored. Both gravitational loading (opening moments) and wind uplift (closing moments) were considered.

Liquid storage tanks are used to preserve liquids such as oils, water, petrochemical fuels, nuclear fuels, etc. It is crucial to protect these structures against strong dynamic forces, such as earthquakes. For a given structure, the seismic risk is evaluated for a defined damage state, considering the appropriate intensity measure. The selection of intensity measures is crucial, and it is determined by the criteria of efficiency and sufficiency. In this study, an attempt is made to identify optimal intensity measures for liquid storage tank base-isolated by laminated rubber bearing. Here, peak isolator displacement is considered as an engineering demand parameter, and the efficiency and sufficiency analyses are performed for several intensity measures. Additionally, a parametric analysis is carried out by considering different tank slenderness ratios. It is observed that the average spectral acceleration for the broad tank and spectral acceleration at the isolation period for the slender tank are efficient and sufficient intensity measures. These results can be used in assessing the fragility and seismic risk of liquid storage tank base-isolated with laminated rubber bearing.

The AA 2014-T6 series of Aluminum is widely utilized in aerospace and defense applications as an airframe in missiles etc., due to its lightweight, strength, and resistance to corrosion. In current defense operations, low-velocity projectiles are employed to neutralize enemy targets within buildings. The present challenge is to evaluate the damage caused by the low-velocity projectile such that it does not cause significant structural damage to the building without compromising its functionality of neutralizing the enemy targets. To assess the stability of a building, it is crucial to study the stability of columns, as they play a significant role in maintaining the building's structural stability. Steel tubular sections are frequently used in modern constructions due to their structural efficiency and aesthetic appearance. This study focuses on investigating the impact of low-velocity projectiles(AA 2014-T6) on steel columns through various numerical analyses. Quasi-static and high strain rate characterization of aluminum and steel materials are performed to derive Johnson–Cook parameters from experimental tests. The obtained parameters were imported to Abaqus for numerical studies, where models were created using a projectile with an impact velocity of 20 m/s. The model is analyzed by varying parameters such as column thickness and the cross-sectional shape of the column. The results showed that as the column thickness increases, the deformation of the projectile increases while the out-of-plane deformation of the column decreases. Conducting experimental investigations on projectile impact is expensive and time-consuming; hence, the findings from the numerical analysis of this study form the basis for designing an experimental program to validate the results, which can be the future scope of this study.

India is currently experiencing an infrastructural boost and is in the midst of building many new structures as well as upgrading the existing ones. The upgradation of the existing structural systems generally involves changes due to new codal provisions, change of use, addition of excess loads due to installation of new components, et cetera. Following modifications, structure might not be able to meet code specified requirements. In the earthquake prone regions in India, these vulnerabilities call for the evaluation and subsequent strengthening. This study involves the comparison of provisions made for seismic evaluation and strengthening of the reinforced concrete buildings in ASCE-41(2017) and IS 15988 (2013). Both the codes provide methodology for identification of the deficiencies in the buildings. In case of IS 15988, the evaluation is limited and is unable to provide any decisive outcome and further suggest appropriate retrofit method. Whereas ASCE-41 has a systematic tier-wise methodology with increasing order evaluation and identify need for strengthening. This paper involves the review and comparison of the evaluation techniques outlined in ASCE 41 and IS 15988. In addition to comparison, this article also involves a case study performed on actual building based on ASCE-41 evaluation. This comparative analysis aims to bridge the gaps in the present IS 15988 and ASCE-41 and suggest the improvements which can be incorporated in subsequent versions of IS 15988.

Concrete structures are a vital component of modern infrastructure, but they are subjected to cracking over time due to environmental and structural factors. In addition to allowing access to dangerous and corrosive chemicals in concrete, cracks also allow water to seep through the structural members, accelerating the corrosion of reinforcement and damaging the aesthetics of the structure. Traditional visual inspection methods are time-consuming and expensive and often result in subjective interpretations, thereby necessitating automated crack detection techniques. Convolutional Neural Networks (CNNs) are a type of Deep Learning algorithm that has shown remarkable performance in image classification, object detection, and segmentation tasks. Transfer Learning can fine-tune pre-trained CNN models like GoogLeNet, VGGNet and ResNet with high accuracy and reduced overfitting, even with a limited training dataset. In this study, ResNet is fine-tuned using publicly available datasets of images of cracks on concrete surfaces. Subsequently, the trained model is used to detect cracks on a 1:8 scale reinforced concrete slab culvert built in the laboratory and subjected to bidirectional seismic excitation on a shake table. OpenCV has been adopted to extract features, such as crack width, orientation, and shape, from the detected cracks, which can be used for further analysis, such as crack classification, severity assessment and damage evaluation. The key findings from this study indicate that CNN coupled with OpenCV can be a viable alternative to manual crack inspection and analysis tasks. The application can be extended to help structural engineers identify the condition and extent of damage in large-scale structures, like bridges and dams, using camera-equipped unmanned aerial systems (UAS).

The need for high-rise buildings, towers, and offshore constructions has significantly expanded as a result of urbanisation, thereby increased the requirement for piling foundations. One of the most critical aspects of pile design is the evaluation of the vertical settling of a pile. Numerous studies have been performed on single-pile and pile raft foundations that are subjected to vertical loads, and the present study aims to look at how vertical loads affect various single-pile and raft foundations. A parametric study is also performed to investigate the effects of various pile types, soil characteristics, the existence of a strong or weak soil inter-layer, and vertical settlement of a single pile under vertical load. The load settlement behavior of single pile made of concrete, timber, and steel has been analyzed and stress and settlement along the pile depth are evaluated for all the piles for structural design. Steel pipe piles have several advantages over concrete piles, including durability, high load-bearing capacity, excellent quality, and a fast construction time. In this study, numerical modelling of single pile made of concrete, timber and steel has been analyzed as three-dimensional analysis in ABAQUS finite element software. A numerical model based on the Mohr–Coulomb soil model and a linear elastic pile model has been examined.

This study attempts to investigate the performance of a slope bottom tuned liquid damper (TLD) for mitigating the earthquake response of reinforced concrete (RC) framed structure. Time history analysis of a 10-story RC framed structure, with installation of a flat bottom rectangular TLD, and a slope bottom (dual triangular case) rectangular TLD has been performed. Structure-TLD system is analysed for input of five different types of earthquake time histories. The important findings of study are being presented in terms of frequency ratio, liquid mass reduction and response reduction due to slope at TLD’s bottom. The analysis is being performed for TLD, considering dual triangular slope at the base, with slope angles varying from 0 to 25°. Investigations show that frequency ratio of TLD reduced with rise in dual triangular slope at TLD’s bottom. The reduction in mass of liquid with slope is being observed to be linear, and an optimum slope angle for the reduction in structural response was observed to be around 20°.

The study of ballistic impact behavior of plain concrete target slabs having unconfined uniaxial compressive strength as 48 MPa against long steel rod projectile had been carried out through both experimentally as well as numerically. The objective of the study was to obtain the ballistic curve through ballistic experiments and thus validate the experimental findings through numerical modelling using finite element method (FEM) tool i.e., ABAQUS Explicit software. Consequently, validated numerical model was put to further study in order to explore the effect of various end support conditions.

Infrared Thermography (IRT) is one of the non-destructive evaluation techniques used to detect defects in a structure based on temperature differences due to the presence of air voids. Depth estimation of the defects can be done by various post-processing methods after obtaining thermograms over a period of time. Most prevalent methods require knowledge of the thermal properties of the sound area, which is typically challenging to ascertain in the field. Based on the experimental surface temperature response of the sound area in the field specimen, this study endeavors to estimate the unknown parameters of the specimen. This inverse heat transfer problem is done by updating a finite element model with a trust region reflective algorithm. The experiment is conducted by heating a GFRP-wrapped surface of a concrete slab with halogen lamps, and subsequently recording the transient response of the surface temperature with a thermal camera. The thermal properties of concrete and GFRP were estimated using the proposed algorithm, which closely matched actual physical values.

In this study, an experimental investigation has been carried out to assess the fatigue life of butt-welded connections made of high-strength S700 steel. A total of 15 specimens, consisting of butt-welded steel with S700MC grade, are subjected to high-cycle fatigue testing. The testing is conducted at a constant frequency of 30 Hz and with a stress range ranging from 50 to 85% of the yield stress. The stress ratio (R) for this study is set at 0.1. Using two different approaches, the natural fitting approach, and the slope m fixed approach, the S–N curve is developed at the conclusion of this research. The fatigue strength of the weldment made with S700MC grade steel is found to be approximately 50–64% higher than the values suggested by the Eurocode.

The present study investigates and evaluates the energy absorption characteristics of the Aluminum-based Carbon fiber/epoxy resin laminates (Al-CF FMLs) experimentally and numerically. The composite laminate fabricated with carbon fiber and aluminum layers was impacted by a steel projectile with near Mach velocity using bullet impact rig. The velocity of projectile before and after the event of impact was determined to calculate amount of energy dissipated. The validation of the numerical model was simulated in LS-Dyna® and ballistic resistance and effect of obliquity was studied. The outcomes of this study provided the understanding of the Al-CF FMLs being capable of efficiently absorbing energy at higher impact velocity and higher obliquity of the projectiles. This study reveals that FMLs are most efficient as impact shield for impact velocities near their ballistic limit.