Beam-Column Joints Reinforcement Detailing Adequacy in Case of a Corner Column Loss-Numerical Analysis

Abstract This study investigates the behavior of reinforced concrete (RC) beam-column joints at the corner panel after a ground corner column loss scenario. The ductility of a frame is dependent on the ductility of its components, particularly its joints. Deficiency in joints performance can be related to an unexpected event. For example, the removal of a ground corner column turns the joint above into an inverted knee joint, and also inverses the direction of the resulted bending moments in the adjacent exterior and interior joints. Throughout this work, the effects of these changes are evaluated numerically using different modeling techniques considering both seismic and non-seismic reinforcement details. Numerical simulations of standard and sub-standard joints that were verified against experimentally tested joints are also presented. Joint macro models are developed using the OpenSees platform. These numerical models are then used to simulate the substandard beam-column joints appearing in RC frames after ground corner column removal. Moreover, strut and tie models (STMs) were developed for a substandard knee joint to validate the obtained numerical results. The application of the developed numerical models allows to identify the evolution of a joint’s capacity in function of its reinforcement detailing. The analysis shows the suitability of seismic detailing for exterior and interior joints and also a decrease in the inverted knee joint resistance and this can be recovered by adding i) more confinement to the joint panel zone or ii) joint vertical stirrups. An increase in the degree of confidence in the numerical results is achieved by reproduce similar behavior using different analysis methods.

摘要 本研究针对地面角柱拆除场景下，角区板带内钢筋混凝土（reinforced concrete，RC）梁柱节点的力学行为展开探究。框架结构的延性取决于其组成构件尤其是节点的延性，节点性能不足可能引发突发失效事件。例如，拆除地面角柱会使上方节点转变为倒置膝状节点，同时反转相邻外侧与内侧节点的弯矩作用方向。本研究采用多种建模技术，结合抗震与非抗震配筋构造细节，对上述变化带来的影响开展数值评估。本研究还给出了经试验验证的标准与劣构节点的数值模拟结果。研究基于OpenSees平台开发了节点宏观模型，并利用该数值模型模拟了地面角柱拆除后钢筋混凝土框架内出现的劣构梁柱节点。此外，本研究还针对劣构膝状节点开发了撑杆-系杆模型（strut and tie models，STMs），以验证所得到的数值模拟结果。通过应用所开发的数值模型，可明确节点承载能力随配筋构造变化的演化规律。分析结果表明，抗震配筋构造适用于外侧与内侧节点；而倒置膝状节点的承载能力会出现下降，但可通过两种方式予以恢复：一是对节点板带区域施加更强的约束，二是增设节点竖向箍筋。本研究通过采用不同分析方法重现相似的力学行为，提升了数值结果的可信度。