Shear Failure Mechanism of Reinforced Concrete Columns and Beam-Column Joints under Tri-lateral Excitations and Prevention Design Method

通过三维梁柱组合体试件试验，研究柱或梁柱节点剪切破坏对钢筋混凝土框架结构在轴向和双向荷载作用下抗震性能的影响。两个试件是从中高层R/C框架的第一层移除的大约一半比例的模型，并且在平面图的角部位置具有纵向和横向正交的梁的两个柱。一个试件被设计为柱剪切破坏，另一个被设计为梁柱节点剪切破坏。将钢制测力传感器放置在整跨梁的中心，测量作用在梁上的轴力和剪力。在对R/C梁试件中心的力传感器进行校准的补充试验中，验证了力传感器不会妨碍梁在反向循环荷载下的滞回性能。双向剪切力和变化的轴向载荷 ...更多信息 在R/C组合试验中，每个柱顶同时施加从压到拉的荷载d。两个样本均以假定的方式失效，即，一个是柱中部的剪力，另一个是梁柱节点板的剪力。柱破坏时，剪切裂缝首先发生在柱的外侧。通过对两个尺寸和配筋方式与三维组合试件相同的柱进行单向和轴向加载试验，研究了单向和双向加载对柱抗剪性能的影响。通过在柱的顶部和底部提供反对称弯矩来进行测试。试验中内柱保持受压轴力不变，外柱从受拉到受压施加变化的轴力。两个单独的柱受到单向荷载反向剪切失败。柱的整个表面均布有多条斜向剪切裂缝。而在三维亚组合试件中，剪切裂缝主要集中在柱体中部。双向荷载作用下的内柱和外柱的抗剪强度分别是单向荷载作用下的0.78倍和0.86倍。少

Objective of the study is to investigate the influence of shear failure in columns or beam-column joints on earthquake resistant performance of a R/C frame building subjected to varying axial and bi-lateral loads by testing three-dimensional beam-column subassemblage specimens. Two specimens were approximately half a scale model removed from first story in middle-rise R/C frame, and had two columns with orthogonal beams in longitudinal and transverse direction at comer position of a plan view. One specimen was designed to fail by column shear and the other by beam-column joint shear. Force transducer made from steel was placed at the center of full-span beam to measure both axial force and shear force induced to the beam. In supplementary test to calibrate the force transducer incorporated in the center of R/C beam specimen, it was verified that the force transducer did not hamper hysteretic behavior of a beam under reversed cyclic loading. Bi-lateral shear forces and varying axial loa … More d from compression to tension were applied simultaneously at each column top in R/C subassemblage test. Both specimens failed in supposed manner, i.e., one by shear at the middle portion of columns and the other by shear in beam-column joint panels. In column failure specimen, shear cracks occurred in the exterior column at first. However, shear failure in the interior column became remarkable due to bi-lateral shear loading.Two isolated columns with the same dimension and steel arrangement as the three-dimensional subassemblage specimen were tested under uni-lateral and axial loading to investigate the difference of shear performance caused by uni-lateral or bi-lateral loading. Tests were carried out by providing anti-symmetric bending moments at the top and bottom of a column. Compressive axial load to interior column was kept constant through testing whereas varying axial load was applied to exterior column from tension to compression. Two isolated columns subjected to uni-lateral load reversals failed in shear. Many diagonal shear cracks occurred uniformly in entire surface of a column. On the contrary, shear cracks concentrated in the middle region of columns in the three-dimensional subassemblage specimen. Shear strength of interior and exterior columns subjected to bi-lateral loading was 0.78 times and 0.86 times smaller respectively than that of corresponding isolated columns subjected to uni-lateral loading. Less