Numerical Model of Cold Press-Formed Square Steel Tube Columns Considered with Degradation Behavior due to Local Buckling and/or Fracture

摘要

In steel building structures, local buckling and/or fracture of columns could occur during strong ground motions, furthermore complete collapse might be induced due to the column strength degradation. In this paper, cold press-formed square tube columns are targeted, and numerical model being able to trace precisely degradation behavior is proposed. In order to take account of both local buckling and fracture with low computational costs, multi-spring model which consists of some uni-axial springs is adopted. Axial force-deformation relationships of uni-axial springs are provided on flat area and corner area of square tube severally, and are separated into skeleton part and hysteresis part. All parameters on force-deformation relationship are identified based on finite element analysis results of short columns under monotonic or cyclic axial loading. Comparing between analysis results by multi-spring models and past cyclic loading test results or finite element analysis results, it is clarified that degradation behavior of cold press-formed square steel tube columns can be traced with high accuracy.