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Summary: To better meet the evolving requirements of industrialized building system, this paper introduces a novel approach by proposing the utilization of a plate‐reinforced composite (PRC) coupling beam, which incorporates a steel bar truss deck as a substitute for the conventional reinforced concrete (RC) slab. In order to study the effect of different types of RC slabs on the performance of PRC coupling beams, the low‐cyclic reversed loading test was carried out on three PRC coupling beams. The differences of failure modes, load bearing capacity, stiffness degradation, and energy dissipation capacity of each coupling beam are analyzed. The finite element software ABAQUS is used to analyze the stress distribution in the concrete, steel plate, and reinforcement skeleton of the novel coupling beam. The results show that the incorporation of a steel bar truss deck in PRC coupling beams with a small span‐to‐depth ratio can effectively enhance their shear bearing capacity and energy dissipation capacity. The inclusion of a slab significantly enhances the load‐bearing capacity of the coupling beam, while the utilization of a steel bar truss deck in PRC coupling beams greatly improves their overall bearing capacity. The PRC coupling beams featuring a steel bar truss deck exhibit superior load capacity compared to those with conventional RC slabs. The cumulative energy dissipation at the damage point in PRC beams with a steel bar truss deck is 1.39 times greater than that of the coupling beam without slabs and 1.18 times higher than that of the coupling beam with traditional RC slabs. [ABSTRACT FROM AUTHOR]

AbstractAs CFRP (carbon fiber-reinforced polymer) offers high retrofit efficiency for structural members in bending and shear due to its superior mechanical properties compared to steel, sheets made from this material have become ubiquitous in strengthening existing reinforced concrete (RC) structures. However, there needs to be more research on RC beams with no stirrups that have been shear-strengthened with side-bonded CFRP sheets. As such, this study aims to investigate this specific topic and assess design-related parameters that impact the load-bearing capacity of these shear-strengthened beams. To achieve this, nonlinear finite element models of four RC beams, including one control beam and three beams strengthened with side-bonded CFRP sheets, were built and verified regarding shear capacity, crack patterns, and failure mechanisms. The simulated beams demonstrated a high level of accuracy in all mentioned aspects. Numerical models were then developed to evaluate the design-oriented parameters that affect the response of shear-strengthened beams, including the concrete compressive strength, the amount of steel reinforcement, the number of CFRP layers, the CFRP bonding configuration, and the shear span-to-effective depth ratio. The results showed that not only the compressive strength of the concrete but also the amount of steel longitudinal reinforcement had a significant relationship with the load-bearing capacity of shear-strengthened beams. Meanwhile, the bonding configuration and the layer number of side-bonded CFRP sheets considerably influenced the ductility, the crack pattern, and the failure mode of shear-strengthened beams. [ABSTRACT FROM AUTHOR]

Despite of intensive research on concrete fatigue, the transfer of fatigue characteristics determined at the material level to the structural level remains a challenging issue. In this paper, the propagation of fatigue‐induced damage through the concrete structure is analyzed using a microplane fatigue model for concrete recently developed by the authors. To this end, our recent experimental study in which the fatigue propagation was monitored at the structural level represented by prestressed concrete beams is used to derive a general interpretation of the stress redistribution process using of the developed model. The numerical studies show that the developed microplane fatigue model provides a powerful computational tool for in‐depth analysis of the correspondence between the fatigue behavior at the material and structural scales in a wide range of load configurations. In addition, the thermodynamically based constitutive model allows for the quantification of the energy dissipation during the process, revealing the possibility of deriving material‐specific energetic characteristics that can further help to make the predictions of fatigue life more accurate. Highlights: Structural experiments validate the constitutive fatigue hypothesis.Damage‐induced energy dissipation is an objective value for fatigue characterization.Insights into the fatigue life extension of concrete at the structural level are provided.Structural stress redistribution induces variable load amplitudes at local level. [ABSTRACT FROM AUTHOR]

This study investigates the structural behavior of reinforced concrete (RC) flat slabs supported on edge columns and the influence of eccentricity direction on their punching shear strength. For this purpose, code provisions were compared based on the ultimate capacities of experimental tests reported in the literature. The comparison included the approaches provided by the current Eurocode 2, fib Model Code 2010 and the final draft of the second generation of Eurocode 2 (FprEC2). Then, a numerical investigation was conducted in which full‐scale slabs tested by Albuquerque et al. (2016) were simulated. Numerical analyses were carried out in the software Diana using a total strain‐based crack model to simulate the concrete nonlinear behavior. The input parameters for the simulations were obtained through a stochastic calibration approach to account for uncertainties related to the concrete properties. A reasonable agreement was found between the calibrated numerical models and the experimental results regarding load‐deflection curves and crack patterns. Furthermore, important differences were identified in the failure mode of edge column‐slab connections subjected to inward and outward eccentricities. Finally, additional simulations were carried out to obtain a full shear‐moment interaction diagram and investigate the shear distribution at the control perimeters around the column. The proposed method in FprEC2 exhibited a good estimation with a relatively low scatter of the punching resistance of flat slab‐edge column connections analyzed in this work. [ABSTRACT FROM AUTHOR]

The application of reinforced concrete modular integrated construction (MiC) has gained popularity in Hong Kong, but challenges still exist in the temporary tying of side walls during composite wall construction. This paper presents an innovative inner tie system for composite walls, applied in a MiC project in Hong Kong. The system's components are installed on the side walls of precast modules in the factory without the need to penetrate through the walls. After transport to the site, by rotating the loop on-site to engage the hook, the tying effect is achieved during on-site concrete pouring between the interstitial space of two modules. This system eliminates the use of tie bolts that penetrate precast side walls, allowing for comprehensive interior fitting-out in the factory and minimizing disruptions to internal decoration during on-site construction. The paper presents the system's mechanism, nonlinear Finite Element Analysis (FEA) simulation, section size optimization, and validation through tensile and punching shear tests. Furthermore, an instrumented mockup module assembly was carried out, and the system was eventually applied in a real MiC project. The system can effectively control the horizontal deformation of MiC module side walls within a limit. Compared to current existing tying methods, this system offers easy installation, load-bearing reliability, adaptability to certain construction errors, savings on manpower and construction time, and also a decrease in construction waste and carbon emission. It will provide a valuable reference for future MiC projects. [ABSTRACT FROM AUTHOR]

Steel plates for welded steel bridge members typically supported on three or four edges. Average compressive stress–strain curves and ultimate strength are vital for assessing the stability of these plates. These metrics also form the foundation for developing beam-column models that account for local buckling. However, collecting this data presents significant challenges. This study comprehensively discusses the factors influencing the determination of average compressive stress–strain curves and ultimate strength for bridge steel plates under uniaxial longitudinal compression. Factors such as element type, mesh size, boundary conditions, solution method, the effect of plate thickness, and aspect ratio are discussed, leading to establish rigorous shell or solid finite element models. This investigation aids in standardizing steel plate analysis. Representative panels of bridge steel plates are investigated to establish the database of compressive stress–strain curves using the developed shell finite element model. A new formula is presented to predict the ultimate strength of these plates. This database supports the creation of a beam-column theoretical model incorporating local buckling to analyze bridge steel members with high efficiency. [ABSTRACT FROM AUTHOR]

WE PRESENT A NONLINEAR FINITE ELEMENT ANALYSIS to investigate the buckling and post-buckling behaviour of functionally graded material (FGM) plates resting on the elastic foundation. The material properties are assumed to vary gradually across the thickness according to a power law distribution. The starting point of the investigation is the generalized third-order plate theory and the Vlasov model of elastic foundation having properties varying throughout the depth. The plates are subjected to bending to verify the formulation and compression loads including buckling and post-buckling analysis to investigate the influence of various parameters on the structural response. [ABSTRACT FROM AUTHOR]

This study investigates the effectiveness of a hybrid solution that combines carbon fiber-reinforced polymer (CFRP) systems for the flexural and shear strengthening of T-cross section reinforced concrete (RC) beams. The hybrid solution consists of near-surface mounted CFRP laminates for flexural enhancement and externally bonded U-shaped CFRP strips for shear strengthening. Moreover, an innovative CFRP anchorage system is proposed to prevent premature debonding of the U-CFRP strips and to improve their shear contribution. To address the limitations of the experimental program and propose an efficient and design-oriented simulation approach for NSM-EBR strengthening RC beams with the innovative anchorage system, a comprehensive numerical investigation was conducted by considering the key parameters affecting the performance of the strengthened system. This paper presents the results of an experimental program and a nonlinear finite element analysis that simulate the behavior of the materials up to their failure and the bond conditions between CFRP and concrete. This study also includes a numerical parametric study to assess the effectiveness of the proposed strengthening concept with several possible scenarios, as well as the predictive performance of the fib Bulletin 90 and ACI 440.2R-17 formulations. [ABSTRACT FROM AUTHOR]

In this study, a static load test of prestressed steel-reinforced concrete simply supported beams was carried out utilizing three test beams to investigate the bond–slip effect between the section steel and concrete in prestressed steel-reinforced concrete beams. Finite element models of three beams considering two different bond–slip constitutive relations and without considering bond–slip performance were developed in ABAQUS. The influence of shear bolt nails on the bond slip between the section steel and concrete was analyzed, and the load–slip curves of the three test beams were also computed. Generally, the results showed that the finite element calculations considering the bond–slip effect are more consistent with the experimental calculations, and the bond–slip constitutive relationship proposed by Yang Yong is more suitable for the numerical simulation of prestressed steel-reinforced concrete beams. When the effective prestress is increased from 222.15 KN to 279.61 KN, the ultimate bearing capacity increases by 14.8%. When the concrete strength is increased from 37.21 MPa to 47.97 MPa, the ultimate bearing capacity increases by 15.2%. When the stirrup ratio is 0.50%, compared with 0.25%, the ultimate bearing capacity increases by 7.8%. When the steel content is 5.41%, compared with 3.37%, the ultimate bearing capacity increases by 9.1%. The results of this study can provide a reference for future research and engineering applications of bond slip between section steel and concrete in prestressed steel-reinforced concrete beams in the future. [ABSTRACT FROM AUTHOR]

The automation degree of sealing technology in coal mine is insufficient, and the automatic directional drilling rig can improve the automation degree of sealing. A colloidal slip with double friction force for automatic directional drilling machine is designed to solve the problem that the clamping device of automatic directional drilling machine is bad. Two kinds of colloidal structures are proposed to realize the difference of friction between active drill pipe jointing and unjointing, and to ensure the smooth jointing of drill pipe. Using the nonlinear finite element method, Mooney-Rivlin strain energy function was used to describe the mechanical properties of colloid, and the simulation of colloid clamping hole sealer was carried out. The working friction of colloid of different materials was obtained, and the rationality of the two structural colloids was verified. The influence of the compression amount of adhesive strip on the surface of the colloid on the stress of the hole sealer was studied. The effect of the number of adhesive strips on the colloidal surface on the axial friction force was investigated. The results show that natural rubber and polyurethane rubber are reasonable as colloidal materials, the compression of rubber strips is 0.9 mm, and the number of rubber strips is 3.

Standard non-local gradient damage methodology for fatigue analysis has an intrinsic drawback of unusual widening of the damage zone. This causes a rapid growth of crack in the simulations which often violate experimental evidences. In order to tackle this undesirable behaviour, the localizing gradient damage methodology has been formulated for high cycle fatigue crack growth simulations. The framework comprises of coupling damage and elasticity through continuum mechanics, a fatigue damage law and an interaction function which reduces the influence of damaged regions on the surrounding locality. The present scheme prevents the spurious widening of the damage-band around the critically damaged area and therefore the non-physical growth of fatigue crack in the simulations is successfully countered. The developed framework is tested on various standard specimens under mode-I and mixed-mode high cycle fatigue loads. Nonlinear finite element analysis is used for this purpose. The discretized form of solver equations for the localizing framework is mathematically derived. Numerical examples show that the simulated crack-growth curves using proposed localizing framework agree closely with the experimental data and has a higher accuracy than the standard non-local framework. [ABSTRACT FROM AUTHOR]

This paper investigates how the corrosion process contributes to the reduction of the cross-section, ultimate tensile strength, and ductility of corroded steel reinforcing bars, as well as the bond loss between corroded steel and damaged concrete. Considering such parameters, the finite element models are constructed and validated based on the experimental data obtained from six reinforced concrete (RC) beams into three groups: two control beams, two corroded beams without strengthening, and two CFRP-strengthened corroded beams. The validated model is capable of reflecting the failure mechanism of CFRP debonding that dominates the load-carrying capacity of corroded beams after strengthening. Therefore, the numerical simulations offer a prediction platform for investigating the structural behavior of corroded RC beams strengthened with CFRP (Carbon Fiber Reinforced Polymer) sheets without a new set of experiments. Finally, the results from nonlinear finite element analyses (FEA) help to determine the effect of main parameters affecting the strengthening performance of corroded RC beams, such as concrete compressive strength, longitudinal steel reinforcement ratio, steel/concrete bond strength reduction, flexural strengthening scheme, CFRP length. [ABSTRACT FROM AUTHOR]

This paper describes the 3rd Blind Simulation Competition (BSC) organized by the fib WP 2.4.1 which aims to assess the predictive performance of models based on the finite element method (FEM) for analysis and design of fiber reinforced concrete (FRC) structures submitted to loading and support conditions that promote punching failure mode. Fiber reinforcement is used in an attempt to eliminate conventional punching reinforcement and provide technical and economic advantages. The two tested real‐size prototypes represent a column‐slab interior region of an elevated steel‐fiber reinforced concrete (E‐SFRC) slab where anti‐progressive collapse reinforcement is disposed in the alignment of columns/piles. Despite a punching failure surface being formed in both experimentally tested prototypes at the rupture stage, fiber reinforcement was able to mobilize the yield capacity of the conventional flexural reinforcement, providing high deformation capacity, and ductility to the prototypes. The average post‐peak load‐carrying capacity of the tested prototypes at a deflection seven times higher than the deflection at yield initiation of the conventional reinforcement was still 90% of the average peak load. Regarding the BSC, a total of 26 proposals were received and involved 94 participants from 29 institutions and 17 countries, with 53.9% using smeared crack models (SCMs), 30.8% a concrete damage plasticity (CDP) model, 3.8% discrete crack models (DCMs) and 11.5% considered as “other models.” From these simulations it was verified, in average terms, that SCM assured the best predictive performance apart from the average strain in the SFRC and the maximum crack width which were better predicted by DCM. More accurate predictions were obtained by using in‐house software than by adopting commercial software. [ABSTRACT FROM AUTHOR]

The micro/nano pores in natural mineralized tissues can, to a certain extent, affect their responses to mechanical loading but are generally ignored in existing indentation analysis. In this study, we first examined the void volume fraction of sound and caries lesion enamels through micro-computed tomography (micro-CT). A Berkovich indentation study was then carried out to characterize the effect of porous microstructure on the mechanical behavior of the human enamels. The indentation tests were also modeled using the nonlinear finite element analysis technique to simulate indentation load-displacement curves, which showed reasonable agreement with the experimental measurements. From the simulation results, the extent of densification in the plastic zone was identified and the corresponding stress and contact pressure evolutions were quantified. Further, a conventional elastic-perfectly plastic material model without considering micropores was also developed to investigate the compaction effect of the porous structure. The simulation results reveal that conventional elastic perfect-plastic constitutive models become less reliable to model the mechanical behavior of carious lesion enamel with increasing loss of mineral content as it underestimates the yield stress and plastic energy dissipation. This study divulges the importance of compaction of porous enamel structure beneath the indented area. Note that understanding the effect of porous microstructures on plastic behavior is vital as the involved inelastic deformation mechanism associated with irreversible processes, such as wear and localized microcracking, has a significant bearing on wear and fatigue behavior of enamel. Based on micro-CT and nano-indentation characterization, a numerical model was developed aiming to precisely describe the deformation behavior of naturally porous enamel. Inelastic properties and energy dissipation characteristics of porous enamel were investigated in detail. This work demonstrated that the existence of micro-pores in White Spot Lesions (WSLs) contributes to mechanical stability, which can mitigate the reduction in Young's modulus and fracture toughness resulting from loss of mineral components. The knowledge gained from this study can be used to explain the mechanisms related to irreversible processes, such as contact induced cracking and wear, and strengthen understanding of the mechanical behavior of porous mineralized tissues. [Display omitted] [ABSTRACT FROM AUTHOR]

This study investigates the behavior of hybrid beam-column connections with numerous detailing methods to be incorporated into precast concrete moment-resisting frames under simulated reversed cyclic loading, and ultimately develops a design procedure. Seismic performance of moment-resisting precast concrete beam-column connections was investigated through simulated reversed cyclic load tests. In addition, nonlinear finite element analysis (FEA) of typical monolithic and precast concrete connections was carried out using a modified concrete damage plasticity model. Good agreement was achieved between experimental and numerical results, which indicates that the FEA model is capable of capturing failure modes of the investigated precast concrete connections. Simple detailing modifications resulted in major improvements in the performance of connections in terms of load-displacement curves, stiffness, and energy dissipation. Finally, a design procedure was developed for the investigated connections based on failure modes and investigated limit states. [ABSTRACT FROM AUTHOR]

To realize the prefabricated structure of special‐shaped concrete‐filled steel tubular (CFST) column frame and enhance the level of indoor room utilization, this paper proposed a novel prefabricated frame with special‐shaped CFST columns and H‐shape steel beams connection with side plate. To investigate seismic behavior of this prefabricated frame structure, a 2‐story and 2‐bay CFST frame specimen was fabricated and tested under reversed cyclic loading. The failure mode, hysteresis behavior, degradation of lateral stiffness and bearing capacity, ductility and energy dissipation were analyzed. Experiment results indicated that failure mode presented strong columns and weak beams. Hysteresis curve of frame showed fully shuttle‐shaped. The mean story drift angle was 1/36 at ultimate stage. Equivalent viscous damping coefficient was 0.038–0.464. The bearing capacity degradation was relatively gentle, but the overall stiffness degradation was more obvious. It suggested that the frame had proper seismic and energy dissipation property. After the test, the seismic property of test frame was further investigated through the numerical simulation approach. The failure mode and skeleton curve obtained from the simulation were nearly consistent with test results, indicating that numerical analysis results were precise and with high reference meaning. [ABSTRACT FROM AUTHOR]

This study presents an innovative numerical model based on the position-based finite element method, utilizing laminated frame elements to predict beam displacements under corrosion-a common challenge in reinforced concrete structures due to chlorides and carbon dioxide penetration. The proposed model addresses both geometric and physical non-linearity, specifically considering the uniform reduction in rebar area, a critical consequence of carbonation-induced corrosion. This reduction significantly influences element inertia and, consequently, the structure's stiffness. Given the expected increase in corrosion problems in reinforced concrete structures due to climate change-induced rising temperatures and heightened carbon dioxide levels, resulting in earlier degradation and reduced stiffness, there is a pressing need for alternative approaches to calculate structure displacement under carbonation-induced corrosion. In response to this concern, our model provides an innovative and alternative methodology, demonstrating promising results when compared with existing literature, even under the constraints of a simplified model. [ABSTRACT FROM AUTHOR]

The use of nonlinear, large-deformation, dynamic finite element analysis (FEA) has become a cornerstone in crash test simulations, playing a pivotal role in evaluating the safety performance of critical civil infrastructures, including soil-embedded vehicle barrier systems. This review paper offers a detailed examination of numerical modeling methodologies employed for simulating dynamic soil–structure interactions in crash test simulations, with a particular focus on dynamic impact pile–soil interaction. This interaction is a critical determinant in assessing the effectiveness of soil-embedded barrier systems during vehicular impacts. Our extensive review methodically categorizes and critically evaluates four prevalent modeling methodologies: the lumped parameter method, the subgrade reaction method, the modified subgrade reaction approach, and the direct or mesh-based continuum method. We explore each methodology's underlying philosophy, strengths, and shortcomings in accurately simulating the dynamic interaction between soil and piles under impact loading. This technical review aims to provide a thorough understanding of the critical and distinctive aspects of modeling soil's dynamic responses under impact loading conditions. Moreover, this paper is envisioned to serve as a foundational reference for future research endeavors, steering the advancement of innovative simulation techniques for tackling the dynamic impact soil–structure interaction problem. [ABSTRACT FROM AUTHOR]

The use of nonlinear, large-deformation, dynamic finite element analysis (FEA) has become a cornerstone in crash test simulations, playing a pivotal role in evaluating the safety performance of critical civil infrastructures, including soil-embedded vehicle barrier systems. This review paper offers a detailed examination of numerical modeling methodologies employed for simulating dynamic soil–structure interactions in crash test simulations, with a particular focus on dynamic impact pile–soil interaction. This interaction is a critical determinant in assessing the effectiveness of soil-embedded barrier systems during vehicular impacts. Our extensive review methodically categorizes and critically evaluates four prevalent modeling methodologies: the lumped parameter method, the subgrade reaction method, the modified subgrade reaction approach, and the direct or mesh-based continuum method. We explore each methodology’s underlying philosophy, strengths, and shortcomings in accurately simulating the dynamic interaction between soil and piles under impact loading. This technical review aims to provide a thorough understanding of the critical and distinctive aspects of modeling soil’s dynamic responses under impact loading conditions. Moreover, this paper is envisioned to serve as a foundational reference for future research endeavors, steering the advancement of innovative simulation techniques for tackling the dynamic impact soil–structure interaction problem.

Abstract Previous studies have revealed that the contribution of slab reinforcement to the T-beam flexural strength in negative moment regions are not negligible for the seismic capacity design. An effective slab width (i.e., effective width of flanged section) has been proposed, within which the slab reinforcement needs to be included in the calculation of the beam nominal flexural strength in negative moment regions. These studies mainly focused on the cases using normal-strength steel in moment resisting frames. However, recently high-strength steel has been widely used in reinforced concrete moment resisting frames in high seismic regions to avoid congestion near beam-column joints. The use of high-strength steel may affect the beam stiffness due to the fact that it will require less amount of reinforcement, and result in a different normal stress distribution compared to the case with normal-strength steel. Therefore, this paper investigates the slab reinforcement contribution to the flexural strength of the reinforced concrete T-beam designed with high-strength steel in negative moment regions at exterior beam-column joints, for which nonlinear pushover analyses were conducted. Beam reinforcement grade was considered as a primary parameter with several other design variables including slab thickness, height, and span length of the beam. Analytical results show that the use of high-strength steel can result in a wider effective slab width than the case of normal-strength steel for calculating the beam nominal flexural strength under the negative moment. Based on these results, new design equations were proposed.

The application of reinforced concrete modular integrated construction (MiC) has gained popularity in Hong Kong, but challenges still exist in the temporary tying of side walls during composite wall construction. This paper presents an innovative inner tie system for composite walls, applied in a MiC project in Hong Kong. The system’s components are installed on the side walls of precast modules in the factory without the need to penetrate through the walls. After transport to the site, by rotating the loop on-site to engage the hook, the tying effect is achieved during on-site concrete pouring between the interstitial space of two modules. This system eliminates the use of tie bolts that penetrate precast side walls, allowing for comprehensive interior fitting-out in the factory and minimizing disruptions to internal decoration during on-site construction. The paper presents the system’s mechanism, nonlinear Finite Element Analysis (FEA) simulation, section size optimization, and validation through tensile and punching shear tests. Furthermore, an instrumented mockup module assembly was carried out, and the system was eventually applied in a real MiC project. The system can effectively control the horizontal deformation of MiC module side walls within a limit. Compared to current existing tying methods, this system offers easy installation, load-bearing reliability, adaptability to certain construction errors, savings on manpower and construction time, and also a decrease in construction waste and carbon emission. It will provide a valuable reference for future MiC projects.

This study investigates the effectiveness of a hybrid solution that combines carbon fiber-reinforced polymer (CFRP) systems for the flexural and shear strengthening of T-cross section reinforced concrete (RC) beams. The hybrid solution consists of near-surface mounted CFRP laminates for flexural enhancement and externally bonded U-shaped CFRP strips for shear strengthening. Moreover, an innovative CFRP anchorage system is proposed to prevent premature debonding of the U-CFRP strips and to improve their shear contribution. To address the limitations of the experimental program and propose an efficient and design-oriented simulation approach for NSM-EBR strengthening RC beams with the innovative anchorage system, a comprehensive numerical investigation was conducted by considering the key parameters affecting the performance of the strengthened system. This paper presents the results of an experimental program and a nonlinear finite element analysis that simulate the behavior of the materials up to their failure and the bond conditions between CFRP and concrete. This study also includes a numerical parametric study to assess the effectiveness of the proposed strengthening concept with several possible scenarios, as well as the predictive performance of the fib Bulletin 90 and ACI 440.2R-17 formulations.

Previous studies have revealed that the contribution of slab reinforcement to the T-beam flexural strength in negative moment regions are not negligible for the seismic capacity design. An effective slab width (i.e., effective width of flanged section) has been proposed, within which the slab reinforcement needs to be included in the calculation of the beam nominal flexural strength in negative moment regions. These studies mainly focused on the cases using normal-strength steel in moment resisting frames. However, recently high-strength steel has been widely used in reinforced concrete moment resisting frames in high seismic regions to avoid congestion near beam-column joints. The use of high-strength steel may affect the beam stiffness due to the fact that it will require less amount of reinforcement, and result in a different normal stress distribution compared to the case with normal-strength steel. Therefore, this paper investigates the slab reinforcement contribution to the flexural strength of the reinforced concrete T-beam designed with high-strength steel in negative moment regions at exterior beam-column joints, for which nonlinear pushover analyses were conducted. Beam reinforcement grade was considered as a primary parameter with several other design variables including slab thickness, height, and span length of the beam. Analytical results show that the use of high-strength steel can result in a wider effective slab width than the case of normal-strength steel for calculating the beam nominal flexural strength under the negative moment. Based on these results, new design equations were proposed. [ABSTRACT FROM AUTHOR]

This research aims to conduct a comparative analysis of the first crack load, flexural strength, and shear strength in reinforced concrete beams without stirrups. The comparison is made between the conventional model developed according to the current design code (ACI building code) and an unconventional approach using Artificial Neural Networks (ANNs). To accomplish this, a dataset comprising 110 samples of reinforced concrete beams without stirrup reinforcement was collected and utilised to train a Multilayer Backpropagation Neural Network in MATLAB. The primary objective of this work is to establish a knowledge-based structural analysis model capable of accurately predicting the responses of reinforced concrete structures. The coefficient of determination obtained from this comparison yields values of 0.9404 for the first cracking load, 0.9756 for flexural strength, and 0.9787 for shear strength. Through an assessment of the coefficient of determination and linear regression coefficients, it becomes evident that the ANN model produces results that closely align with those obtained from the conventional model. This demonstrates the ANN's potential for precise prediction of the structural behaviour of reinforced concrete beams. [ABSTRACT FROM AUTHOR]

On February 6, 2023, two major earthquakes (Mw 7.7 and Mw 7.6) occurred in the province of Kahramanmaraş in southern Türkiye at 9-h intervals, causing a lot of loss of life and destruction in the region where approximately 16% of the country's population lives. This study provides a comprehensive summary of common structural deficiencies that occurred in reinforced concrete (RC) buildings in earthquake-prone cities and proposes actionable measures systematically for future disasters. The evaluated data are based on the field observations of the authors. The main reasons for damages in RC buildings in the observation field can be classified into two categories: (1) the errors during the design stage (strong beam–weak column, short column, soft story, pounding effects, the existence of short and unconfined lap splices, insufficient transverse reinforcement, column–beam connection failures), and (2) the errors during the construction stage (poor concrete quality, unribbed reinforcing steel bar and corrosion, incorrect placement of reinforcement bars, incorrect end hook angle and length, weak gable walls, workmanship defects). Furthermore, a comparative nonlinear finite element analysis of the seismic impacts caused by the first earthquake on an existing RC building fully collapsed in the earthquake was conducted as a case study considering Türkiye Building Earthquake Code 2018 [TBEC 2018] "Türkiye Bina Deprem Yönetmeliği," Afet ve Acil Durum Yönetimi Başkanlığı, Ankara (in Turkish)]. The validity and accuracy of the reasons for damages, which were reached by the field observations, were also proven by numerical analysis results. The importance of complying with the regulations, conducting the performance evaluations and controls of the buildings according to the renewed earthquake regulations and, if necessary, repairing–strengthening works were emphasized. The loss of life and property after the earthquakes that we experienced on February 6, 2023, which were called the "Disaster of the Century", showed that Türkiye's current building stock, especially those built before a certain date, is insufficient against earthquakes. [ABSTRACT FROM AUTHOR]

Since cold-formed steel (CFS) elements are susceptible to complex buckling phenomena that decrease their structural capability, many strengthening trends have been developed so far. One of these methods is the use of polystyrene aggregate concrete (PAC) as bracings in order to restrain the global and distortional buckling modes of CFS members, where a new structural system comprising CFS elements encased in PAC has been proposed. In this research, PAC-encased CFS shear panels have been investigated numerically, where a simplified finite element model was developed to predict the structural behavior and capacity of such members. This goal was achieved using ANSYS software, where a geometrically and materially nonlinear analysis with imperfections (GMNI) was used to solve the problem of PAC-encased CFS shear panels. The full detailed volume-contact element-based concrete model was replaced by spring elements perpendicular to the plate’s plane with equivalent properties, and beam elements that could represent the concrete block more accurately regarding the global lateral stiffness and shear resistance. Consequently, for this case, the combination of local and global stiffness of PAC could produce the actual shear behavior of PAC-filled wall panels. The developed model was validated against previous experimental tests from the literature. Parametric studies were conducted in terms of the imperfection amplitudes, the stiffness of springs and the properties of PAC. Finally, the structural performance of PAC-encased panels under combined axial and shear loading was examined, where the effect of different axial load levels on the lateral strength was determined, and an interaction equation was proposed.Article Highlights: An innovative simplified numerical model was developed to predict the shear performance of PAC-encased CFS wall panels. The effect of different imperfection amplitudes and PAC properties on the shear performance of PAC-encased CFS walls were investigated. An interaction curve was proposed to predict the resistance of PAC-filled CFS walls under combined vertical and shear action. [ABSTRACT FROM AUTHOR]

Abstract Since cold-formed steel (CFS) elements are susceptible to complex buckling phenomena that decrease their structural capability, many strengthening trends have been developed so far. One of these methods is the use of polystyrene aggregate concrete (PAC) as bracings in order to restrain the global and distortional buckling modes of CFS members, where a new structural system comprising CFS elements encased in PAC has been proposed. In this research, PAC-encased CFS shear panels have been investigated numerically, where a simplified finite element model was developed to predict the structural behavior and capacity of such members. This goal was achieved using ANSYS software, where a geometrically and materially nonlinear analysis with imperfections (GMNI) was used to solve the problem of PAC-encased CFS shear panels. The full detailed volume-contact element-based concrete model was replaced by spring elements perpendicular to the plate’s plane with equivalent properties, and beam elements that could represent the concrete block more accurately regarding the global lateral stiffness and shear resistance. Consequently, for this case, the combination of local and global stiffness of PAC could produce the actual shear behavior of PAC-filled wall panels. The developed model was validated against previous experimental tests from the literature. Parametric studies were conducted in terms of the imperfection amplitudes, the stiffness of springs and the properties of PAC. Finally, the structural performance of PAC-encased panels under combined axial and shear loading was examined, where the effect of different axial load levels on the lateral strength was determined, and an interaction equation was proposed.

In this study, a static load test of prestressed steel-reinforced concrete simply supported beams was carried out utilizing three test beams to investigate the bond–slip effect between the section steel and concrete in prestressed steel-reinforced concrete beams. Finite element models of three beams considering two different bond–slip constitutive relations and without considering bond–slip performance were developed in ABAQUS. The influence of shear bolt nails on the bond slip between the section steel and concrete was analyzed, and the load–slip curves of the three test beams were also computed. Generally, the results showed that the finite element calculations considering the bond–slip effect are more consistent with the experimental calculations, and the bond–slip constitutive relationship proposed by Yang Yong is more suitable for the numerical simulation of prestressed steel-reinforced concrete beams. When the effective prestress is increased from 222.15 KN to 279.61 KN, the ultimate bearing capacity increases by 14.8%. When the concrete strength is increased from 37.21 MPa to 47.97 MPa, the ultimate bearing capacity increases by 15.2%. When the stirrup ratio is 0.50%, compared with 0.25%, the ultimate bearing capacity increases by 7.8%. When the steel content is 5.41%, compared with 3.37%, the ultimate bearing capacity increases by 9.1%. The results of this study can provide a reference for future research and engineering applications of bond slip between section steel and concrete in prestressed steel-reinforced concrete beams in the future.

In this paper, the mechanics of inflatable drop-stitch panels are investigated, including the impact of large shear deformations, nonlinearity due to wrinkling of the panel skin that occurs under net compressive strain, work done by the confined internal air, and the effect of the drop-stitch yarns on the panel skin stresses. A large deflection finite element (FE) analysis framework is presented that allows for a panel's stability and post-buckling response to be quantified. The FE code is verified through comparison with available analytical solutions, and the impact of critical response drivers is examined. The FE models are then used to explore the capacity of panel walls when used as part of a shelter subject to realistic wind and snow loads and to assess the dependence of the capacity on the important design parameters of inflation pressure and panel depth. The analyses indicate that while the drop-stitch panel capacity is sensitive to the panel depth and inflation pressure, panels with reasonable cross-sectional dimensions are viable for use in structural applications where they must support significant compression and bending. Future work should focus on increasing the structural efficiency and capacity by increasing the panel shear stiffness and operational inflation pressure. [ABSTRACT FROM AUTHOR]

This paper describes an experimental investigation of a novel reinforced concrete buckling-restrained brace for precast concrete lateral load-resisting frame structures in seismic regions. The proposed brace uses ductile reinforcing bars with unbonded lengths across end gaps and bonded lengths at the middle region for lateral stiffness, strength, energy dissipation, and ductility. The experimental program included four isolated diagonal brace subassemblies subjected to reversed-cyclic pseudostatic lateral loading. Local buckling of the energy-dissipation bars across the end gaps is the most critical failure mode that can limit the ductility of the brace in compression. Up to this failure, the bonded and unbonded regions of the braces performed as designed. The results demonstrated the different deformation and stiffness behaviors of the braces in tension and compression. Subsequent loading to large tension displacements provided evidence of the large energy dissipation that can be expected if premature failure of the brace can be prevented. Simplified numerical models provided good predictions of the measured brace behavior until failure. This research featured the first set of tests for this brace, and the results highlighted adjustments needed to design and modeling to achieve the desired behavior of the brace. Recommendations for future research include improved shear dowel and confinement designs to prevent local buckling of the energy-dissipation bars and improved longitudinal reinforcement designs to prevent yielding of the energy-dissipation bars in the middle bonded region of the braces. [ABSTRACT FROM AUTHOR]

In this paper, the residual ultimate strength of large opening box girder with pitting corrosion under combined loads is investigated by ABAQUS software. A primary investigation was first conducted to compare the influences of corrosion types. Afterwards, effects of some studied parameters including the depth, density, volume, and location of the pit, which may affect the ultimate strength, were analyzed based on a series of FE results. It was concluded that the relative corroded volume loss has a non-negligible effect on the residual ultimate strength. For torsion and sagging cases, the side plates' pits significantly reduce the ultimate strength. For the hogging case, the effect of bottom plate pitting on the ultimate strength should be paid attention to. The interaction relationship between torsion and bending moment was analyzed. An interaction equation is proposed for evaluating the ultimate strength of large opening box girders with pitting damage under combined loads. [ABSTRACT FROM AUTHOR]

Numerous studies have shown that incorporating fibers in concrete can improve its mechanical properties, including tensile strength and toughness. Due to these outstanding properties, the use of fiber‐reinforced concrete (FRC) composites has been investigated for applications in structural members subjected to shear, in which brittle failure mode may occur. An example of this type of application is the use of high/ultrahigh‐performance fiber‐reinforced concrete (HPFRC/UHPFRC) in flat slab‐column connections as an alternative to shear reinforcement. The experimental results revealed that the use of advanced concrete materials led to an increase in the punching shear and deformation capacities. Despite these advantages, the use of HPFRC/UHPFRC in practical design is somehow limited by the lack of guidelines in codes for this type of new material. Furthermore, the study of constitutive models for nonlinear finite element analysis is also necessary. In this regard, this article addresses the simulation of two‐way slabs with HPFRC, subjected to concentrated monotonic vertical loading, tested in a previous experimental study, where the HPFRC was used only in a limited slab region around the column, and the rest of the slab was cast with normal strength concrete. The numerical models were developed in the commercial finite element software DIANA. The concrete nonlinear behavior was modeled by a total strain‐based constitutive model, in which the HPFRC softening is represented by a tensile stress‐crack width (σ − w) relationship. The validity of the numerical model is checked by the comparison with the experimental results and a punching shear mechanical model, leading to the formulation of a closed‐form equation. Finally, a parametric study was conducted to extrapolate the results obtained in the experimental campaign and to optimize the use of HPFRC to obtain a more economical and sustainable solution. [ABSTRACT FROM AUTHOR]

Graphyne is a material that has unique mechanical properties, but little is known about how these properties change when the material has holes. In this work, the effect of hole geometry, considering circular, triangle, and rhombus hole configurations, on the mechanical nonlinear response of γ-graphyne structures is studied. Graphyne, graphdiyne, graphyne-3, and graphyne-4 structures are under investigation. An efficient nonlinear finite element analysis (FEA) method is adequately implemented under large deformations for this purpose. The study varied the size and shape of the holes to understand how these changes affect the nanostructure's mechanical response. The results indicate that the hole geometry significantly impacts the mechanical nonlinear response of γ-graphyne structures. The holes' size and shape affect the structures' elastic behavior, deformation, and strength. The findings can be used to optimize the design of γ-graphyne structures for specific mechanical applications. The study highlights the importance of considering the hole geometries in the design and fabrication of these materials. [ABSTRACT FROM AUTHOR]

Prefabricated post-tensioned prestressed concrete (PTC) girders with high degrees of prestressing have been developed continuously in recent bridge designs to reach longer spans, higher quality, and larger load-bearing capacity. However, during the prefabrication process, several inclined and horizontal cracks were observed at the ends of a new style post-tensioned concrete girder, which could have a negative impact on the girders' longevity. In this study, a nonlinear finite element analysis technique was utilized to illustrate how concrete reacts and the mechanisms behind typical cracking patterns during the actual post-tensioning sequence. The prestressing load of a PTC girder was simulated with an improved cooling temperature method that accounts for immediate prestress losses. The field of principle tensile strain patterns and primary strain trajectories explained the overall mechanism underlying typical cracking behaviors. The results showed that the horizontal cracks under the anchorage plate (behavior 1) were generated by the bursting force, whereas the inclined cracks (behavior 2) and the horizontal cracks between the strands N1 and N2 anchor plates (behavior 3) were caused due to the spalling force. The effects of self-weight, girder end forms, as well as the transfer length of the prestressing strands, were discussed. The result demonstrates that both the self-weight and girder end shapes have a considerable effect on the behaviors of the anchorage zone. It is suggested that the transfer length of the anchor head be greater than 26 times of strand diameter to achieve the same effective stresses as the theoretical values. [ABSTRACT FROM AUTHOR]

Abstract This work focuses on the failure mechanisms of concrete hydroelectric facilities affected by alkali–aggregate reaction (AAR). Identification of potential failure mechanisms is based on an original “top-down approach” using an AAR pushover analysis with multi-physics numerical simulation of a representative hydroelectric facility. Different global rehabilitation scenarios based on slot-cutting and grouting techniques are discussed and compared, using different performance metrics. A new quantitative performance metric, specifically developed for the nonlinear sophisticated analysis tool and considering the volumetric cracking caused by AAR is also suggested. Based on comparison results, a combination of grouting after a partial slot-cutting in the neighborhood of the discontinuities, appears to provide the best compromise in terms of stress relief and extent of cracking. New AAR benchmark problems, issued from the top-down approach, are also suggested for the first time in the literature.

Civilian buildings have been imposed to blast loading, resulting in irrecoverable damages and casualties. This paper studies the analytical and numerical performance of concrete slabs reinforced by Conventional Steel Rebars and Perforated Steel Plates based on the values recommended by ASCE Blast-Resistant and nonlinear Finite Element Analysis performed in Abaqus. ASCE Blast-Resistant proposes the equations covering the burst of any explosive materials, while Abaqus uses the TNT equivalent mass method. This study uses PSP as an alternative to CSR in concrete slabs because PSPs are more integrated with surrounding concrete than CSRs due to the particular geometry of the holes. In the analytical phase, based on ASCE Blast-Resistant, the nonlinear performance of the rectangular concrete slab reinforced with CSR under blast loading was determined. Then, in the numerical step, the square concrete slab reinforced with CSR subjected to blast loading was simulated and verified with the literature results. Furthermore, a nonlinear finite element simulation of the rectangular concrete slab was performed to validate the modeling. Moreover, the simulation results of the rectangular slab were compared with the analytical results calculated based on ASCE Blast-Resistant, revealing that the equivalent mass method used in Abaqus accurately simulates the behavior of the reinforced concrete slab under blast loading. Finally, CSRs were replaced by PSPs with an equal volume in the rectangular concrete slab to compare their performance showing that PSPs with equal volume compared to CSRs can reduce the reinforced concrete slab's maximum displacement by up to 20% and decrease its following wavelength.

The construction of strut‐and‐tie models (STMs) is the key, but also the difficulty when the model is used to describe the force mechanism and guide the reinforcement layout design of concrete disturbed regions (D‐regions). Topology optimization is a promising way to guide STMs construction. Different from the existing construction methods of predetermining nodes, the angle of inclination of the truss elements is first determined to ensure that it is consistent with that of the principal stresses in a 2D finite element model of the structure. The constructed model can well reflect the force transmission path of structural members, and it is better than the existing methods when it is evaluated through the principle of minimum strain energy. To verify the validity of the STM, a reinforcement layout scheme is adopted completely according to the position of the tension ties. On this basis, another reinforcement layout scheme adds additional transverse reinforcements in the bottle‐shaped stress field. The nonlinear finite element comparative analysis of an irregular deep beam designed by the two schemes is carried out. The results show that the two ultimate loads are close. Brittle failure occurs in the former, while the latter has higher deformability and eventually ductile failure occurs. [ABSTRACT FROM AUTHOR]

Allowable compressive rail force due to track‐bridge‐interaction for ballastless track On modern continuously welded railway tracks on bridges the rails are exposed to additional axial stresses due the interactions between the track and the bridge. On ballasted track the total compressive force within the rail must be limited to prevent rail buckling. In the 1980s extensive theoretical and experimental research was conducted and a limit value for the additional compressive rail stress of 72 MPa was introduced. For the more ridged ballastless track systems this limit value was raised to 92 MPa. However, this was done without any transparent scientific basis. For the case of the Itz Valley Bridge on the new highspeed line between Ebensfeld and Erfurt the calculated additional stresses due to the track‐bridge‐interaction could not be verified with these limit values. To determine a new case specific limit value for the additional compressive rail stresses extensive investigations were conducted and are presented within this article. The behaviour of the ballastless track system under high compressive rail forces was analysed numerically and experimentally. As a result, failure mechanisms and limit states were defined and verified for secure combinations of input parameters. This example shows the potential of the system to withstand high compressive rail forces and presents a possible method to define new limit values for the additional compressive rail stresses for ballastless track systems on bridges. [ABSTRACT FROM AUTHOR]