Zhen-Hao Wu

A steel–concrete composite beam with a straddle monorail is a lightweight and easily installable structure. The mechanical performance of group stud connectors and their arrangement are key design parameters that govern the beam’s overall performance. This study investigates the behavior of group stud connectors by conducting push-out tests on four specimens, comprising three full-scale models and one 1:3 scaled model. Variables such as the number of connectors, arrangement, and specimen size were explored. The results indicated that all the specimens exhibited ductile failure due to stud shearing. The strain distribution analysis revealed higher strain at the edges and lower in the middle, persisting as the load increased. The group stud effect resulted in a 23.4% to 27.2% reduction in shear capacity for the full-scale specimens and 16.5% for the scaled specimen. The reduction was proportional to the density of the studs, but the size effects were less significant. This study provides valuable insights into the mechanical behavior of group stud connectors and offers design recommendations for practical applications.

In this research, the seismic performance optimization of a Y-eccentrically braced composite frame (Y-EBCF) was conducted. An efficient fiber beam–spring element model, which considers the spatial composite effect of the RC slab, was proposed and used to simulate the research objects. A genetic algorithm (GA) was developed for the Y-EBCF, and the chromosome coding method, fitness function, termination condition, and the selection, crossover, and mutation operators were specified. This algorithm was then applied to the optimization problems of arrangement strategies of the eccentric braces and mechanical parameters of shear links for a typical 10-storey composite frame building under different acceleration excitations. The results indicated that, compared to the traditional enumeration algorithm, the proposed GA could find the optimal solution rapidly for the seismic performance optimization problems of the Y-EBCF. The computation cost of the GA for the optimization problems involving the arrangement strategies of the eccentric braces and mechanical parameters of shear links was only 1.5% and 2.6% of those of the enumeration algorithm, respectively. A subsequent parametric analysis revealed that the calculation cost of the GA could be further reduced by adjusting the values of population size, selection, and mutation ratio.

Uplift-restricted and slip-permitted (URSP) connectors have been demonstrated to effectively enhance the anti-cracking performance of RC slabs in negative moment areas. While their efficacy is recognized, studies of composite frames utilizing URSP connectors remain scarce, limiting their application in construction. This research undertakes a numerical analysis of the seismic performance of steel–concrete composite frames that employ URSP connectors. The influence of key design parameters on seismic behavior is scrutinized. Leveraging prior tests on composite frames with URSP connectors carried out by the authors’ group, a sophisticated three-dimensional FEM model is crafted. This model, built using the ABAQUS software (2016), accounts for the intricate mechanical behaviors of shear connectors. The fidelity of the FEM model is validated through a juxtaposition of numerical and test outcomes, assessing strain distribution, damage patterns, and load–displacement curves. This numerical model serves as a basis for the study, exploring the impacts of three crucial design parameters on structural seismic performance. The findings suggest that the arrangement length of URSP connectors should be constrained to less than half of the frame beam’s span to optimize mechanical performance during seismic events. Additionally, enhancing both the flange thickness and the steel beam’s height is recommended to further bolster structural integrity.

Single-column elevated station structures are irregular structures with long-span cantilever beams and individual pier columns in the transverse section. The uneven mass and stiffness in the horizontal and vertical planes necessitate research on the seismic performance of these structures. This study performed a nonlinear response-history analysis (NRHA) of a single-column elevated station structure using the finite element program MSC.MARC and analysed its seismic performance under different seismic intensities. The stress states of the primary components were evaluated, and the effect of vertical earthquake motion on the seismic performance of the structure was considered. The torsional behavior caused by the uneven mass and stiffness in both horizontal and vertical directions should be considered, and energy dissipation measures should be taken to reduce the internal force and deformation of the bottom-pier columns and second-floor columns in the process of designation to improve the seismic performance of the structure. A bidirectional pushover analysis (BPA) was applied. The load amplification factor was adjusted to optimize the BPA results. The results of the modified BPA were similar to those of the NRHA, indicating the computational reliability of the modified BPA. The modified BPA method was accurate, applicative, and efficient. The BPA can improve computational efficiency compared to NRHA and can be widely applied in the structural design process for practical engineering applications.