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This paper introduces a topology optimization approach based on the virtual element method (VEM), incorporating uncertainties. The objective of this optimization process is to design an optimal material layout for problems governed by linear elasticity equations to minimize the volume while satisfying probabilistic compliance constraints. The VEM is used to solve the boundary value problem in reliability-based topology optimization (RBTO). In the comparison between the VEM and the standard finite element method (FEM), a key difference emerges in the absence of explicitly defined shape functions tied to discrete degrees of freedom in VEM. Unlike FEM, VEM directly constructs the discrete bilinear form and load linear form without the need for computing shape function derivatives within the elements. This flexibility accommodates meshes with intricate geometries and arbitrarily shaped elements. The paper discusses the computational efficiency of VEM RBTO and explores the geometric impact of tessellations on converged topologies, demonstrating reduced susceptibility to checkerboard patterns compared to conventional quadrilateral elements. Additionally, the single-loop approach is examined, showcasing comparable accuracy to the first-order/second-order reliability methods (FORM/SORM) of RBTO using VEM. Numerical results for several problems that demonstrate the feasibility of the proposed method are presented. [ABSTRACT FROM AUTHOR]

When designing steel members with nonsymmetric cross sections, it is essential to consider twisting effects when performing stability checks via second-order analysis according to the ANSI/AISC 360-22. Existing line-element formulations for nonsymmetric sections are mostly derived based on thin-walled assumptions, leading to an overestimation of member strength due to the inaccurate prediction of member behavior, especially when the cross sections have moderate wall thickness. This paper proposes an efficient line-element method for second-order analysis of steel members with nonsymmetric thick-walled sections considering the warping degree of freedom (DOF) and the twisting effects along with the transverse shear deformations. Additionally, a two-dimensional (2D) finite-element cross section analysis method employing the constant strain triangle (CST) element is developed to calculate the section properties for arbitrary cross sections, including the Wagner and the shear coefficients. The proposed method is implemented in the educational structural analysis software MASTAN2 and verified through two sets of examples. [ABSTRACT FROM AUTHOR]

The discrete-like crack model (DLCM), a crack-analysis scheme incorporated with the nonlinear finite element method, is redeveloped for parallelism. The algorithm of the new DLCM based on the theory of bond redistribution is implemented through the OpenMP interface and enables analyses of a 50-story building with more than four million degrees of freedom. The analysis considers the drying shrinkage and creep during the construction and service periods, static pushover loading, and a time history of a near-fault strong ground motion. The amount of cracks is quantified as the total length that occurs on the concrete surfaces. The structural damage due to compression softening exhibits a strong correlation with the length of cracks with opening widths larger than 2 mm. The analyzed building becomes unrepairable when the total length of the >2 mm wide cracks exceeds 50 m. However, the occurrence of such serious damage induced by any seismic vibrations ever recorded is unlikely. "There's no art to find the mind's construction in the face," so King Duncan said. However, we can consider the search for structural damages on concrete surfaces a form of art. The presence of cracks proves the life of a reinforced concrete building, similar to a person's history engraved as wrinkles and scars on their face. Our novel parallel numerical scheme, namely, the discrete-like crack model (DLCM), traces not only the long history of a building starting from its construction but also resolves the issue of unexpected near-fault pulse-type earthquakes into detailed profiles. In this case study, DLCM is employed to assess structural damage using a percentage of cracks that extend up to 100 km on the entire concrete surfaces of a 50-story residential building. The profiles of cracks, stresses, and strains articulate the building's past and current status and render the possibility to improve the quality of living in the future. [ABSTRACT FROM AUTHOR]

Bearing-type bolted connections are frequently used for steel structure connections and are typically small when used to connect high-strength steels. However, studies on the failure mode and ultimate bearing capacity of high-strength–steel-bearing-type bolted connections are, to our best knowledge, limited. To address this gap, experiments and numerical analysis were carried out to investigate bearing-type bolted connections with end distances and edge distances ranging from one time the bolt hole diameter to two times the bolt hole diameter. Eighteen specimens were fabricated using Q460, Q550, and Q690 alloys. The results showed that the specimens exhibited three failure modes: net cross-sectional; tearout; and splitting failures, where end distance and edge distance were two controlled parameters that determined the failure modes. This study introduces a novel data-driven method that leverages accumulated data from finite element models to accurately quantify the boundaries of various failure modes. It eliminates the requirement for numerous assumptions in complex mechanical derivations, specifically when deriving splitting failure boundaries resembling the bending of deep beams. Consequently, this method provides a reliable and feasible alternative for evaluating failure modes in specimens. It was demonstrated that the net cross-sectional failure could be avoided when end distance equaled one time the bolt hole diameter, indicating that it is feasible to lower the minimum of end distance to one time the bolt hole diameter. The ultimate bearing capacity with nonet cross-sectional failure increased linearly with end distance and nonlinearly with edge distance. Ultimate bearing capacity calculation methods for different failure modes considering end distance and edge distance, were proposed, and their accuracy was verified using experimental results from other studies. [ABSTRACT FROM AUTHOR]

T-shaped reinforced concrete (T-RC) beams are widely used in high-rise buildings due to their advantages of reduced concrete usage, low sectional stress, and decreased weight of the structure. However, the calculation method of residual flexural stiffness of T-RC beams has limited existing research. To address this knowledge gap, a comprehensive experimental investigation was conducted, comprising fire tests, dynamic tests, and static load tests on 10 T-RC beams. The aim was to analyze the effects of fire time and load ratio on the residual flexural stiffness of composite beams. The experimental results showed that the residual flexural stiffness of T-RC beams decreased with increasing fire time and load ratio. However, the impact of fire time was more significant than the load ratio. A refined finite element model of T-RC beams under high temperature and after high temperature was established by modifying the frequency data of the dynamic test and considering the impact of cracks. The model accurately predicted the temperature field and deflection change of T-RC beams under fire. Furthermore, a method for calculating the residual flexural stiffness of T-RC beams considering the effect of fire was proposed and validated against the measured values. The proposed method demonstrated a low error rate of less than 10%. [ABSTRACT FROM AUTHOR]

Low-rise brick masonry buildings are considered the most vulnerable type of structures when they are subjected to seismic excitation. Base isolation is considered a widely adopted strategy to enhance the seismic performance of low-rise brick masonry buildings. Previously developed sliding-based isolation systems did not specifically determine the most adequate combination of isolation layer thickness and the recentering mechanism that will result in the best isolation performance. Accordingly, this study investigates the identification of the best-performing configuration of the previously developed base isolation system through extensive numerical studies and experimental verification. The critical parameters considered in this research are the suitable thickness of the isolation layer and the spacing of the recentering rebars. A finite element analysis was conducted on a 1∶3 reduced scale unconfined brick masonry wall model. The first set of models was having a constant isolation layer thickness of 63.5 mm and four different values of recentering rebars spacings (i.e., 152.4, 203.2, 254, and 304.8 mm). The second set of numerical models consists of varying isolation layer thicknesses such as 50, 63.5, and 76 mm, and a constant recentering rebars spacing of 152.4 mm. It was concluded that the suitable value of isolation layer thickness is 63.5 mm with recentering rebars located at a distance of 152.4 mm because it gives the maximum amount of seismic energy dissipation. Later on, the isolator was experimentally verified using a reduced scale unconfined brick masonry wall subjected to displacement controlled cyclic loading tests. Finally, a case study was conducted to verify the performance of the proposed isolator in a full-scale school building. [ABSTRACT FROM AUTHOR]

The interface force condition on the cross section of parallel steel wire strands is an important basis for studying the longitudinal friction and slip behavior of wires. In this study, force-chain superposition was proposed to solve the transmission and distribution of transverse forces between parallel wires. The calculation rules for the basic parameters in the solution were determined, and a wire-drawing experiment was designed to verify their applicability. A two-dimensional discrete model corresponding to the cable cross section was established. According to the source and characteristics of the transverse load, the force system is decomposed into two directions to form two force chain analysis paths so that the model assumptions can be applied properly. A recursive algorithm was proposed to solve the two force chains, and symmetry conditions were applied at the coupling position to make the system self-consistent. The normal forces acting on the interface points were obtained by superimposing the results onto the two force chains and were verified against finite element analysis (FEA) results. A long-span cable-stayed bridge was considered as an example to investigate the interface force condition of its cables, based on which the approximate development length of the broken wires and the interface extrusion force of the multilayered beam model were established. The results indicate that the slight twisting of the parallel wire strands under the action of a large cable force provides 85% of the total interface forces, and the normal force is significantly concentrated in the central area of the cross section. The approximate development length of the central wire is only 25.9% of that of the outermost wire, and the minimum slip friction force between the layers accounts for only 21.2% of the maximum value for the multilayered beam model, confirming that the interface force condition has a significant impact on the longitudinal friction and slip behavior of cable wires. [ABSTRACT FROM AUTHOR]