In this work, a tied braced frame (TBF) was developed to achieve uniform inelastic deformation in an eccentrically braced frame (EBF) by connecting links across the entire frame height with tie members. Herein, a TBF design method is proposed, considering a new lateral force distribution pattern. To better evaluate the seismic performance, and verify the design advantages of the TBF, nonlinear time-history analysis and fragility analysis were conducted using 6-, 10-, and 20-story TBF models designed using this method, as well as EBF models for comparison. It was found that the maximum inter-story displacement angles of the TBF model were reduced by 10%, 3.3% and 6.3% at the 84th percentile at 6, 10 and 20 stories, respectively, and the DCF values were also reduced by about 5.5%, indicating that the design of the TBF structure is more reasonable. The results revealed that the TBF models featured more uniform distributions of the normalized link shear forces and inter-story drift ratios, resulting in a better damage distribution and more ductile behavior. Furthermore, under earthquakes, the tie axial forces were similar to those calculated using the design equation, thereby indicating the reliability of the design method. Under the same seismic conditions, the PGA values of the TBF structure are about 10~15% lower at 50% exceedance probability compared to the EBF structure; the CMR values of the 6-story, 10-story, and 20-story models are 1.12, 1.09, and 1.06 times higher than those of the EBF structure, respectively. Notably, based on a comparison of the exceedance probability from the fragility analysis results for the TBF and EBF models, the TBF model exhibited better anti-collapse performance.

To reasonably evaluate the damage degree of a single-layer spherical mesh shell structure during an earthquake, we develop an improved two-parameter nonlinear combined damage model based on the existing Park-Ang damage model for mesh-shell structures by subtracting the displacement of the elastic phase from the displacement term and adopting the form of a nonlinear combination of the displacement term and the energy dissipation term. Based on material damage accumulation, 144 sets of numerical models covering different spans, rise/span ratios, roof masses, and member sizes were developed and fitted to obtain the values of the parameters to be determined in the damage model, and then, an improved Park-Ang two-parameter damage model for mesh-shell structures was proposed. The critical values of damage indices of the structure at the four performance points were 0, 0.3, 0.7, and 1. The validity of the two-parameter damage model was verified using a single-layer spherically mesh shell structure with three different structural parameters. The results revealed that the improved Park-Ang two-parameter damage model has a damage value of zero in the elastic phase, which satisfies the lower bound convergence and has a good computational accuracy and small dispersion. In addition, the index values of the four performance points reflect the performance status of the mesh-shell structure, indicating that the improved Park-Ang damage model is suitable for evaluating the damage evolution process of the structure under seismic action. This proposed damage model lays a foundation for vulnerability analysis and seismic risk assessment of mesh shell structures, a basis for post-earthquake repair, the development of an optimal design for mesh shell structures, and the analysis of casualty and economic loss statistics.

To study the seismic behavior and influencing factors of prefabricated steel frame composite joints, cyclic loading tests of two groups of scaled specimens were carried out, and the refined numerical model was established and its validity was verified. The failure mode, hysteretic behavior and moment-rotation curve of composite joints and pure steel joints were compared, and the influence of composite slab on the mechanical properties of joints was summarized. At the same time, the parameters of the key components were selected as variables to study the changing law of the stress properties of the joints. The results indicate that the main failure modes of the overhanging end plate connection are end plate yield, bolt breakage and stiffener buckling, and the composite joints will also have local crushing of composite slab. The factors that significantly affect the bearing capacity and initial rotational stiffness of joints include the thickness of end plate, the setting of end plate stiffener, the extension of end plate, the strength of steel, the thickness of slab and the diameter of steel bars. In addition, the shape of end plate stiffeners has obvious influence on the stress distribution of joints. Finally, the calculation model of the overhanging end plate connection composite joint’s initial rotational stiffness was proposed, and the stiffness superposition method was used to consider the bending stiffness of the end plate. At the same time, its reliability and high accuracy were verified, which was of great significance to engineering application.