Evaluation of Ultimete Limit State Strength of Steel Structures

本研究的目的是找出在地震或风荷载作用下，框架的输入能量耗散到极限状态时的破坏机制。试验分为静力试验、地震反应试验和风荷载下的动力反应试验三种。所有试验均在三层框架上进行，并采用在线试验技术进行控制。试验结果总结如下：(1)对于完全弹塑性材料，静力试验中观察到的强度远远高于简单塑性分析计算得到的强度。为了正确评估框架的强度，在框架强度分析中考虑应变硬化效应是非常重要的。(2)惯性力的轨迹沿着表示第一模态振动时惯性力之间的比值的线排列。提出了用等效静荷载来表示动荷载效应的可能性。在框架高振型影响相对较小的情况下，有可能发展出以等效静力参数为特征的简单极限状态抗震设计方法。考虑框架风速与受风墙体风速的交互作用，框架各层的动荷载分布近似等于静荷载分布。然而，在动力响应中，第一模态振动占主导地位。各层静剪力所做功与动荷载所做功之比之间不存在交互关系。

The purpose of this study is to find the failure mechanism of frame in ultimate state which dissipates a input energy to the frame by earthquake excitations or wind loading.There were three types of tests conducted static tests, earthquake response tests and dynamic response tests by wind loading.All these tests were conducted on 3-story frames and were controlled by the On-line test technique.The test results are summarized below:(1) The strength observed at the static tests is much higher than the strength which is calculated by a simple plastic analysis for perfectly elastoplastic materials. In order to evaluate correctly the strength of frame, it is very important to take into account the strain-hardening effect at the strength analysis of frame.(2) The trajectories of the inertial forces are crowed along the line representing the ratio between the inertial forces during the 1st mode vibration. It suggests the possibility of representing the dynamic load effects by an equivalent static load.It is possible to develop the simple ultimate state aseismatic design method characterized by equivalent static parameters, in the case of comparatively small effects of higher mode of vibration in frames.Considering the interactive effects between velosity of frame and wind verosity at the wall exposing to the wind, the dynamic loading distribution exerting at the each floor of frame is nearly equal to the static wind loading distribution. The 1st mode vibration in dynamic response, however, are dominant. Then, there are no interactive relation between the ratios of the work done by the static shear force at the each floor and by the dynamic loads.