Evaluation of Ultimete Limit State Strength of Steel Structures

本研究的目的是找出框架在极限状态下的破坏机理，即在地震激励或风荷载作用下耗散输入能量。本研究进行了三种类型的试验，包括静力试验、地震反应试验和风荷载作用下的动力反应试验。所有这些试验都是在三层框架上进行的，并由在线测试技术控制。试验结果总结如下：（1）在静态试验中观察到的强度远高于通过对理想弹塑性材料的简单塑性分析计算出的强度。为了正确评价车架的强度，在车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在第一模式振动期间惯性力之间的比率的线聚集。提出了用等效静荷载来表示动荷载效应的可能性，在框架高阶振型影响较小的情况下，可以发展出以等效静力参数为特征的简单的极限状态抗震设计方法，考虑框架速度与迎风面风速的相互作用，在框架结构中采用等效静力参数进行抗震设计是可行的。作用在框架各层上的动荷载分布与静风荷载分布基本相等。动力响应中的第一阶振型占主导地位。此时，各层的静剪力所作的功与动荷载所作的功之比之间不存在相互作用关系。

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.