THEORETICAL ANALYSIS AND EXPERIMENTAL RESEARCH ON STABILITY BEHAVIOR OF STRUCTURAL STEEL TUBE AND COUPLER FALSEWORK WITH X-BRACING

摘要

This paper presents a systematic study on stability of the structural steel tube and coupler falseworks with X-bracing (hereinafter referred to as STCF with X-bracing) through experimental and analytical investigations. Two full-scale STCF specimens were constructed and static tests were conducted in the lab in order to get the strength and failure modes of typical STCF with X-bracing. Test data from literature on two full-scale STCF specimens with same geometric parameters but without X-bracing are also adopted for comparison to investigate the effect of X-bracing on its structural property. Advanced nonlinear finite element analysis was conducted on the specimen models using ANSYS in order to study the capacity and failure modes of the tested specimens. Based on the FEA results, parametric studies were carried out in order to investigate the influence of various geometric parameters on the capacity of STCF with X-bracing. Based on the experimental and analytical results, it seemed that the typical failure mode of STCF with X-bracing was that only upper two storey posts and the U-head buckled evidently about the short axis, and other lower posts deformed little which can be negligible, and the findings reveal that the existence of X-bracing causes an evident increase to the load carrying capacities of STCF, especially of STCF without additional spans. It is clear that the strength of the STCF with X-bracing system would 1) increase linearly with the right-angle coupler rotational stiffness, thickness of steel tube to a certain extent; 2) decrease linearly with post spacing, initial imperfection, the storey height to a certain extent; 3) decrease nonlinearly with the U-head height, the sweeping staff height, which has little effect on the failure load of STCF with X-bracing at initial stage and large effect at later stage.