UTILIZATION OF STEEL FIBRES IN DIAGONALLY REINFORCED CONCRETE COUPLING BEAMS AS ADDITIONAL TRANSVERSE REINFORCEMENTS

The purpose of this study is to investigate the effects of transverse reinforcement such as crossties or steel fibers on the cracking and hysteretic behaviors of diagonally reinforced coupling beams aligned vertically over coupled special structural walls. Four 1/3-scale short beams were made and tested under cyclic shear in a double curvature condition. All specimens have the same reinforcement configuration except for transverse reinforcing details and the clear span length-to-section depth ratio (ln/h) of 2. Control coupling beam (CCB) was designed with full confinement of diagonally reinforced concrete beam section based on the seismic design provisions of the ACI 318-14 Code. The other specimens include simplified transverse reinforcement to improve the constructability while retaining adequate strength and ductility. Test results revealed that transverse reinforcement in the diagonally reinforced coupling beams have a significant effect on the cracking and structural behaviors. For fully confined coupling beams with diagonally oriented reinforcement and without crossties and hoop legs, the addition of steel fiber at volume fraction of 0.75% to concrete provides equal cracking and structural behaviors as compared to those of diagonally reinforced coupling beam with full confinement details.本研究旨在探究拉结筋（crossties）或钢纤维（steel fiber）这类横向配筋（transverse reinforcement），对竖向对齐于连体特种结构剪力墙的斜配筋连体连梁（diagonally reinforced coupling beams）的开裂性能与滞回性能的影响。本次试验制作了4根1/3缩尺比例的短连梁试件，并在双曲率受力工况下开展往复剪切试验。所有试件除横向配筋构造不同且净跨高比（ln/h）均为2之外，其余配筋配置均保持一致。对照连体连梁（CCB）依据美国混凝土协会（ACI）318-14规范的抗震设计条款，采用对斜配筋混凝土连梁截面实施全约束的设计方案。其余试件则采用简化的横向配筋构造，在保证足够强度与延性（ductility）的前提下提升施工便利性。试验结果表明，斜配筋连体连梁中的横向配筋对其开裂性能与结构受力行为具有显著影响。对于采用斜向配筋、无拉结筋与箍筋肢（hoop legs）的全约束连体连梁，在混凝土中掺入体积掺量0.75%的钢纤维，可获得与采用全约束构造的斜配筋连体连梁相当的开裂性能与结构受力行为。