Design of Concrete Gravity Load Systems for Lateral Displacements

在北岭地震中，许多钢筋混凝土结构部分或全部倒塌。一些倒塌是由于柱的破坏，这些柱是为重力荷载而设计的。许多工程师根据柱的弯矩强度进行评估。这是一个不合适的方法，因为真正的问题是旋转能力，而不是力矩能力。这里进行的研究将调查这个问题的两个方面。首先是开发分析工具，用它来预测一根柱子在不失败的情况下所能承受的层间漂移。所采用的方法是建立轴向力与曲率能力的相互作用图，而不是传统的轴向载荷与弯矩能力的相互作用图。曲率与旋转有关，反过来可以用来预测层间的漂移能力。竖向加速度和抗剪强度将在分析中考虑。创新柱的细节将开发，将允许更大的非弹性旋转前失效。一种方法是使用框架的抗侧荷载部分所需的完整抗震联系来详细说明所有柱。其他细节将取决于在柱端提供局部灵活性或提供局部约束以防止破裂和/或剪切破坏。这些列的细节将是简单的，经济的，便于检查和建设将推荐。这是北岭地震项目。＊＊＊

9416466 Stanton A number of reinforced concrete structures collapsed, either partially or totally, in the Northridge earthquake. Some of the collapses were attributed to the failure of columns which were designed for gravity loads only. Many engineers perform the evaluation in terms of the moment strength of the columns. This is an inappropriate approach because the real issue is rotation capacity and not moment capacity. The research undertaken here will investigate two aspects of the issue. The first is to develop analytical tools with which to predict the story drift that a column can undergo without failure. The approach to be used is to construct interaction diagrams relating axial force to curvature capacity, rather than the conventional axial load to moment capacity. Curvature is related to rotation which in turn can be used to predict story drift capacity. The vertical accelerations and the shear strength will be taken into consideration in the analysis. Innovative column details will be developed that will permit larger inelastic rotations before failure. One approach is to detail all columns using the full seismic ties required in the lateral load resisting part of the frame. Other details will be developed that depend on either providing local flexibility at the column ends or on providing localized confinement to prevent bursting and/or shear failure. These column details which will be simple, economical, and easy to inspect and build will be recommended. This is a Northridge Earthquake project. ***