Axial Compressive Behavior of PBL-Stiffened Double-Skin Composite Walls Considering Circumferential Gaps

This paper investigates the axial compressive behavior of perfobond rib (PBL)-stiffened double-skin composite walls with circumferential gaps. Axial compression tests were first conducted on three specimens with different gap ratios to examine the failure mode, load-shortening response and strain development. Finite element models were then developed and validated against the test results, and a parametric study was subsequently carried out to quantify the effects of gap ratio, steel ratio and material strengths on the axial resistance. The results show that circumferential gaps do not alter the basic failure mode, which remains governed by outward local buckling of the steel faceplates accompanied by crushing of the infilled concrete, but they reduce the peak resistance and weaken the post-peak response. The reduction in axial resistance is mainly attributed to the weakened steel–concrete interaction before the peak load, while the local re-contact developing after the peak contributes little to the peak resistance. The reduction factor generally decreases with increasing gap ratio and is also affected by the material strengths and steel ratio, which can be represented by a strength-ratio index. Based on these results, a simplified evaluation model is proposed by expressing the axial resistance as the intact-wall resistance multiplied by a reduction factor related to the gap ratio and strength-ratio index. The proposed model provides acceptable prediction accuracy within the investigated parameter range and should be interpreted as a design-oriented simplified evaluation approach.