To develop the cold-formed steel (CFS) building from low-rise to mid-rise, this paper proposes a new type of CFS composite shear wall building system. The continuous placed CFS concrete-filled tube (CFRST) column is used as the end stud, and the CFS-ALC wall casing concrete composite floor is used as the floor system. In order to predict the seismic behavior of this new structural system, a simplified analytical model is proposed in this paper, which includes the following. (1) A build-up section with “new material” is used to model the CFS tube and infilled concrete of CFRST columns; the section parameters are determined by the equivalent stiffness principle, and the “new material” is modeled by an elastic-perfect plastic model. (2) Two crossed nonlinear springs with hysteretic parameters are used to model a composite CFS shear wall; the Pinching04 material is used to input the hysteretic parameters for these springs, and two crossed rigid trusses are used to model the CFS beams. (3) A linear spring is used to model the uplift behavior of a hold-down connection, and the contribution of these connections for CFRST columns are considered and individually modeled. (4) The rigid diaphragm is used to model the composite floor system, and it is demonstrated by example analyses. Finally, a shaking table test is conducted on a five-story 1:2-scaled CFS composite shear wall building to valid the simplified model. The results are as follows. The errors on peak drift of the first story, the energy dissipation of the first story, the peak drift of the roof story, and the energy dissipation of the whole structure’s displacement time–history curves between the test and simplified models are about 10%, and the largest one of these errors is 20.8%. Both the time–history drift curves and cumulative energy curves obtained from the simplified model accurately track the deformation and energy dissipation processes of the test model. Such comparisons demonstrate the accuracy and applicability of the simplified model, and the proposed simplified model would provide the basis for the theoretical analysis and seismic design of CFS composite shear wall systems.

The long-span multi-tower suspension bridge is widely used in the construction of river and sea crossing bridges. The load-bearing safety and anti-sliding safety of its main cable are directly related to the structural safety of a suspension bridge. Failure mechanisms of the main cable of a long-span multi-tower suspension bridge are discussed. Meanwhile, the tribo-corrosion-fatigue of main cable, contact, and slip behaviors of the saddle and service safety assessment of the main cable are reviewed. Finally, research trends in service safety assessment of main cable are proposed. It is of great significance to improve the service safety of the main cable and thereby to ensure the structural safety of long-span multi-tower suspension bridges.

The fire resistance of cold-formed steel (CFS) structures is receiving increasing concern in fire safety design. With the purpose of improving both fire performance and construction efficiency, a new CFS joist–autoclaved lightweight concrete (ALC) composite floor was developed, and a detailed fire experiment on five full-scale floor assemblies was performed. The results showed that the fire resistance of the floor assembly with a double layer of gypsum plasterboard ceiling and a load level of $2.0\mathrm{kN}/{\mathrm{m}}^2$ was extended from 75 to 83 min by the use of 35-mm thick rock wool insulation that was laid firmly between adjacent steel joists during construction; heat transfer to the compression flange of the steel joists was delayed significantly under fire conditions. The fire resistance of floor assemblies increased with decreasing load levels, but such behavior might become insignificant once the steel joists were directly exposed to fire as the ceiling finish fell off. It also was determined that the fire performance of Bolivian magnesium board was considerably better than that of gypsum plasterboard, extending fire resistance approximately 30 min in the tests. All assemblies experienced local compression failure of the top flange and the adjacent lip and web at the midspan of joists, and showed the fire resistance ratings beyond 60 min. The CFS composite floor with a ceiling configuration of only a single layer of Bolivian magnesium board demonstrated substantial competitive advantage in cost and efficiency, and was recommended for potential applications in midrise CFS structures.