Cyclic behavior and hysteresis model of beam-column joint under salt spray corrosion environment

Abstract

This paper aims to investigate a method predicting the cyclic behaviors of welded beam-column joints exposed to the salt spray corrosion environment based on the analysis of the quasi-static tests and numerical simulation results. Experimental results indicated that the reduction of the section caused by corrosion damage was the main factor affecting the degradation degree of bearing capacity and stiffness of the beam-column joints. The rough surface profile and significant corrosion loss of different flanges and webs could be observed for beam-column joints with long-term exposure to the salt spray environment, which had a noticeable influence on the local buckling and fracture of welded zones connecting beam and column, accelerating the failure process. As a result, the number of cycles and the area of the hysteresis hoop gradually decreased as the corrosion degree increased, so that the cyclic deformation capacity and the energy dissipation capacity deteriorated rapidly. When the exposure time was 18 months (the corrosion depth and the maximum pitting depth were 2.13 mm and 1.48 mm), the yield moment and ultimate moment of the beam-column joint decreased by 28.2% and 32.1%, the total rotation and total energy dissipation decreased by 49.4% and 70.8%. A finite element modeling method depended on the shell element was selected to carry out a series of numerical analyses to investigate the impacts of different corrosion factors on the seismic performances of beam-column joints, which pointed out the corrosion damage in the beam and panel zone causing the nonlinear degradation of seismic performance indices, then the linear skeleton curve model of the corroded beam-column joints was proposed. Furthermore, this paper discussed the effects of the plastic post-buckling strength degradation caused by the corrosion damage on the strength and stiffness of hysteresis curves, thereby the cyclic damage accumulation model and hysteresis model which included the characteristic parameters of corrosion was established to predict the hysteresis behaviors of corroded beam-column joints.