Strength and Stiffness-Based Methods for Reducing Hinging in Columns of Reinforced Concrete Frames Subjected to Strong Ground Motion

本项目开展了基于强度和刚度的减少钢筋混凝土框架柱在强震作用下铰接的方法研究。为了减少框架柱中形成铰链的可能性，目前的规定要求框架节点中的柱的总抗弯能力超过大梁的总抗弯能力。该准则的有效性受到实际构件在动力荷载作用下抗弯能力的不确定性的限制。本项目的研究将为框架构件制定具体的强度和刚度准则，以消除框架关键区域的柱的屈服，并在强地震作用下提供最小的局部变形。将开发一种分析程序，以包括构件刚度和随结构高度变化的强度和刚度特性。带软楼层的结构也将在研究中考虑。将为两种情况确定标准，一种情况是消除任何柱子的屈服，另一种情况是将屈服限制在指定的建筑高度的“最佳”水平。选定的标准将使用一系列具有非线性静力和动力分析的比例框架进行评估。此外，几个在北岭地震期间安装了仪器的现有框架将根据现有属性和修改后的属性进行分析，以满足拟议的标准。这项研究有望为建筑框架提供新的强度和刚度标准，以降低建筑框架关键位置柱屈服的概率。

This project carrier out an investigation of strength and stiffness-based methods to reduce hinging in columns of reinforced concrete frames subjected to strong ground motion. Current provisions to reduce the likelihood of hinges forming in the columns of a frame require that the total flexural capacity of the columns framing into a joint exceed that of the girders. The effectiveness of this criterion is limited by the uncertainty of actual member flexural capacities under dynamic loads.The research under this project will develop specific strength and stiffness criteria for frame members so as to eliminate yielding in columns in critical regions of a frame and provide minimum localized distortions during response to strong ground motion. An analytical procedure will be developed to include member stiffness and varied strength and stiffness properties over the height of the structure. Structures with soft stories will also be considered in the study. Criteria will be identified for two situations those that would eliminate yielding of any column, and those that would limit yielding to a specified "optimum" level of building height. The selected criteria will be evaluated using a series of proportioned frames with nonlinear static and dynamic analyses. In addition, several existing frames that were instrumented during the Northridge earthquake will be analyzed based on the existing properties and properties modified to satisfy the proposed criteria. This study is expected to provide new strength and stiffness criteria for building frames that will reduce the probability of columns yielding in critical locations of the building frame.