Experimental analysis of bolts employed as shear connectors in circular concrete-filled tube columns

Abstract This paper presents experimental and theoretical analysis of bolts employed as shear connectors in circular concrete-filled steel tube columns (CFTs). The theoretical results, obtained from ABNT NBR 16239:2013 formulations, were compared with the experimental results. A series of push-out tests were carried out, where the diameter and length of the bolts, the number of connectors and the concrete strength were varied. From the experimental results, it was observed that the equations from ABNT NBR 16239:2013 are conservative. Therefore, it is proposed an adjustment to the formulations in order to consider the concrete confinement. It was also verified that increments in the diameter and the length of the bolt increase the load capacity of the connector. However, the variation of the quantity of bolts and the concrete strength did not interfere in the load capacity.摘要：本研究针对用作圆形钢管混凝土柱（circular concrete-filled steel tube columns, CFTs）抗剪连接件的螺栓开展试验与理论分析。本研究采用ABNT NBR 16239:2013规范公式得到理论结果，并将其与试验结果进行对比。研究开展了一系列推出试验，试验变量涵盖螺栓直径、螺栓长度、连接件数量以及混凝土强度。试验结果表明，ABNT NBR 16239:2013中的相关公式偏于保守。因此，本研究提出对该规范公式进行修正，以考虑混凝土约束效应。同时验证得出，增大螺栓直径与螺栓长度可提升连接件的受剪承载力。但螺栓数量与混凝土强度的变化并未对连接件的受剪承载力产生影响。