Background and Objective: Progressive collapse resistance of the steel moment-frame with composite floor slabs can be assessed by sudden column loss scenarios. In order to investigate the progressive collapse-resistant capacity of the steel moment-frame with composite floor slabs, a simplified approach based on the theory of membrane action and energy equilibrium principle is presented, which assessed the behaviour of progressive collapse resistance of this frame subjected to the removal of a penultimate column via the static and dynamic analysis. Mateial and Method: The residual vertical bearing capacity model considering of the membrane action and tie force (TF) method of composite floor slabs is developed to evaluate the force mechanism of the composite floor slabs. An energy-based theoretical framework is proposed for calculating the maximum allowable dynamic demands based on the nonlinear static Pulldown analysis, which is used to explore the relationship between of dynamic and static response in the progressive collapse process. Furthermore, the finite element software SAP2000 is used to calculate the numerical example to verify the reliability of this simplified approach. Results: The results show that the composite floor slabs significantly improve the structural progressive collapse-resistant ability and this simplified approach evaluates the progressive collapse resistance of the whole structure effectively. Conclusion: The existence of the floor can increase the ductility of the structure, and increase the progressive collapse-resistant ability. The appropriate value of the DIF depends on the ductility and amount of inelastic action the structure would experience during the column removal scenario.

The use of modular steel construction (MSC) achieves a minimum of on-site work and the potential for removability and reuse. In order to realize the overall disassembly of module buildings and the rapid off-site reconstruction after disassembly, special requirements are put forward for the joints of MSCs. The existing joints of MSCs have some problems, such as the difficulty in the erection of the joints for middle column connection and their inability to be reused. In order to solve these key technical problems, an improved version of the demountable self-locking joint is proposed based on the previous plug-in self-locking joint. For this new type of joint, a full-scale test consisting of four specimens was carried out. The results of functional tests verify that the joint has good demountability. The seismic behavior of the joint under seismic load was investigated by cyclic loading tests. Then, finite element (FE) models were developed and validated through the test results. The results of finite element parameter analysis show that joint boxes are very important to the initial stiffness of this kind of joint, but the thickness of the joint box and the diameter of the stud have little influence on the seismic behavior of the joint.

The bond-slip behavior between cold-formed thin-walled steel (CTS) and foamed concrete (FC) is a critical issue in the mechanical performance of FC-filled CTS composite wall structures. Thus, this study provides experimental and theoretical research on the bond-slip behavior between CTS and FC. A total of eleven specimens were tested using push-out configurations, considering the number of web holes, foamed concrete (FC) strength, anchorage length, and CTS section splice form. A constitutive model for bond-slip was proposed, and the regression formulas for accurately predicting the characteristic bond strength between CTS and foamed concrete were established. A finite element model was developed to investigate the bond-slip mechanism at the interface between CTS and FC. The bond-slip constitutive model accurately fits the experimental and finite element results. The results indicate that the ultimate bond strength of the specimens increases with the number of web holes; when the number of web holes reaches two, the ultimate bond strength is 155.4% of that of the non-perforated specimens. As the concrete strength increases from 3.43 MPa to 11.26 MPa, the ultimate bond strength of specimens with two web holes improves by 23.1%, while non-perforated specimens have a 54.7% enhancement. When the anchorage length is extended from 200 mm to 400 mm, the ultimate bond strength decreases by 29.3%. Additionally, when steel sections are joined in a double-span I form, the bond strength increases by 91.6% and 95.8% compared to the single-span form and the double-span box form, respectively.