An eccentrically braced composite frame with a low-yield-point (LYP) steel shear link is an efficient energy dissipation system that exhibits good mechanical properties. However, existing experimental studies have not fully demonstrated the superiority and applicability of the structural system. We present a structural mechanics and finite element model analysis of an eccentrically braced composite frame with a vertical shear link. The effect of the design parameters on the seismic performance of the structure is analyzed. First, a theoretical model of the mechanics of the structural system is established to provide a comprehensive description of the key parameters. Then, a finite element model is developed using the computer program ABAQUS to analyze the mechanical and energy dissipation mechanisms. Finally, the beam-to-column stiffness ratio, shear link web thickness, shear link web width and length, and diagonal brace stiffness are analyzed to determine their effects on the mechanical properties of the structural system. Furthermore, some design parameter values are suggested.

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.

Laminated concrete slabs can deliver desirable structural properties and effectively improve the speed of construction. According to their basic specifications, laminated concrete slabs comprise a 60 mm precast concrete slab and a 70 mm concrete layer cast in situ, with a steel truss bar at a height of 80 mm. This paper studies the effects of the steel truss bar on the mechanical properties of precast slabs. A simple but accurate method is proposed for calculating the stiffness of precast slabs. The test results show that the steel truss bar has a limited effect on the stiffness of the precast slab but will weaken the compression strength of the concrete, resulting in a significant reduction in the ultimate bearing capacity of the precast slab. Further discussions show that eliminating the steel truss bar and appropriately increasing the thickness of the precast slab can effectively increase the stiffness and load-bearing capacity of the precast slab, as well as reduce the consumption of the floor reinforcement by about 26%.

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.

Steel–concrete composite structures have advantages in terms of strong bearing capacity and full utilisation of performance, and thus, composite frame beams are widely used in building construction. However, in the design and use of existing composite frame beams, the composite effect of a slab and steel beam cannot be completely taken into account. In this study, the effective flange width method is utilised to calculate the contribution of the slab reinforcement to the section moment of inertia to check the beam-end crack width via simulations using the general finite-element software MSC.MARC 2020. A parameter sensitivity analysis of the reinforcement tensile stress is conducted to determine critical influential geometric parameters for the side-column and centre-column hogging moment regions. Finally, design formulae for calculating the effective flange widths of the side- and centre-column hogging moment regions are proposed. In the formula for the side-column hogging moment region, the half column width ($R$) and steel-beam height ($h_{\mathrm{s}}$) are critical variables, whereas, in the formula for the centre-column hogging moment region, the steel-beam height ($h_{\mathrm{s}}$), slab width ($b_{\mathrm{c}}$), and half clear-span length ($l$) are critical variables. Both formulas are verified via a multiparameter simulation, which enables more accurate crack-checking calculations for the hogging moment region in the serviceability limit state. This study provides an important reference for fine finite-element simulations of serviceability limit states and shows the factors affecting the effective flange width that differ from those in the ultimate limit state.

Multi-cavity double steel plate–concrete composite structures are composed of two layers of steel plates, accompanied by steel flanges, diaphragms, and a core of concrete. Thanks to their exceptional mechanical attributes, these structures have gained widespread adoption in the field of wind power engineering. The outer steel plates exert a notable confinement on the concrete filling. Nonetheless, there remains a lack of a constitutive model specifically tailored for concrete under confinement within the field of multi-cavity double steel plate–concrete composite structures. To bridge this gap, our research endeavor involved the creation of approximately 2000 shell–solid finite element models, leading to the derivation of a constitutive model for compressed confined concrete within such structures through regression analysis. Initially, theoretical evaluations were conducted to pinpoint the structural parameters potentially influencing confinement behavior. Thereafter, Abaqus shell–solid finite element models were formulated, and their accuracy was corroborated through experimental validations. By systematically adjusting parameters in batch modelling, regression analysis was conducted. Consequently, a constitutive model tailored for uniaxial compression of concrete in multi-cavity double steel plate–concrete composite structures (MDSCCS) was formulated. According to the results, the strength of confined concrete in MDSCCS can be enhanced by up to 23% under typical configurations, as observed in the benchmark model MDSCCS-1. The proposed regression-based confinement model demonstrates a prediction error of less than 15% in 97.8% of the 1342 finite element models that successfully converged in batch simulations.