To effectively adapt to seismic actions in complex earthquake environments and enhance the seismic isolation performance of building structures, this paper divides the disk spring group of traditional disk spring isolation bearings into an upper disk spring group and a lower disk spring group. By arranging different stacking layers, an improved Vertical Variable Stiffness Disk Spring Isolation (VVSDSI) bearing is proposed. The operational performance of this bearing is thoroughly investigated through a theoretical analysis, experimental testing, and numerical simulations. The research results demonstrate the following: (1) under ultimate load conditions, the working stages of the VVSDSI bearing can be divided into two phases. During the isolation phase, the vertical stiffness of the bearing is relatively low, with a value of 11.14 kN/mm, whereas in the protection phase, the vertical stiffness increases significantly to 35.34 kN/mm. (2) During the isolation phase, the preloading displacement exhibits a positive correlation with equivalent stiffness and an equivalent damping ratio, while the loading amplitude shows a negative correlation with these parameters. (3) The theoretical hysteresis model prediction value and numerical model simulation value of the VVSDSI bearing are in good agreement with the measured data, with the maximum errors of the peak load being 6.78% and 10.07%, respectively, which can accurately simulate the mechanical properties of the bearing. Therefore, this research result can provide a theoretical basis and experimental support for the design of vertical seismic isolation systems.

This paper presents a precast concrete composite slab-steel truss formwork system incorporating demountable joints to achieve composite behavior between the upper slab and the lower truss, thereby facilitating truss reuse. The system enables shoring-free construction for medium to long spans(3.0m~6.0m), enhancing construction efficiency and reducing material consumption. To assess its performance under realistic conditions, three full-scale specimens were subjected to vertical static bending tests involving a loading-unloading procedure. A finite-element model was developed and calibrated against experimental results, followed by a parametric analysis. The system demonstrated excellent flexural performance with minimal residual deformations after unloading, indicating high recoverability and reliable reusability. Parametric studies reveal that increasing slab thickness primarily enhances the slab's behavior with negligible influence on the global structural response, whereas truss height and member cross-sections predominantly govern overall stiffness and load-bearing capacity. Based on experimental and numerical findings, simplified design equations for strength and deflection are proposed to support design optimization and practical implementation.

The results of finite element analysis of reinforced concrete Vierendeel sandwich plates (RCVSP) using beam-plate elements calculation model show a significant discrepancy with the actual results. Considering the structural characteristics of RCVSP and the calculation method of beam-elements, the assumption of the existence of nodal stiffness domain effects (NSDE) is proposed for its beam-plate elements calculation model. In order to verify this assumption, the existing experimental data of RCVSP is used to compare with the finite element analysis results of the beam-plate elements calculation model. The analysis results show that there is NSDE in the finite element analysis of RCVSP using beam-plate elements calculation model. The beam-elements calculation model FeaR1, which fully considers NSDE, can effectively restore the calculated stiffness lost. Compared with the solid-elements calculation model of RCVSP, the calculation model FeaR1 is more convenient for modeling, enhances computational efficiency, achieves the stiffness restoration rate of approximately 80%, and maintains the average error of no more than 16%.