Improved equivalent bracing model considering the mechanical properties of hold-downs

Abstract

Hold-downs have a dominant role in the force transmission of a cold-formed steel (CFS) structure, and their mechanical properties have a significant impact on the lateral resistance of the structure. Therefore, a total of 24 specimens of four types of hold-downs were designed and tested, focusing on the impacts of the number of anchor bolts and loading modes on the mechanical behaviour of hold-downs. The test results show that (1) the bending capacity of steel plates, the strength of weld joints, the arrangement of anchor bolts, and the load conditions are the key factors that determine the failure modes and damage degree of hold-downs. Moreover, the load–displacement relationship of hold-downs has obvious nonlinear characteristics. (2) The load and resistance factor design (LRFD) load capacities of the hold-downs significantly decrease with an increase in repeated deformation times. When assessing the load-bearing capacity of a CFS structure during the whole service period, the definition of LRFD load capacities of the hold-downs recommended in AISI S913-13 is conservative. Furthermore, an improved mechanical analysis model of a CFS shear wall that reflects the real mechanical characteristics of hold-downs was established by modifying the commonly utilized equivalent bracing model, and the effectiveness of the model was verified according to previous experimental results. The results confirm that the improved model adequately reflects the anchorage degradation of hold-downs and its influence on the shear properties of a wall, providing a more reliable modelling method for the collapse capacity assessment of CFS structures.