Development of plastic shear link and upgrade of steel structural ductility

本报告旨在发展适用于桥梁抗震耗能的塑性剪力连接概念。进行了12个焊接1截面试件的循环剪切试验。试件的长度和高度分别为2240 mm和800 mm，腹板厚度分别为4、5和7 mm。腹板由垂直加强筋分隔成两个800 mm宽的正方形面板。法兰的宽度和厚度分别为300 mm和12 mm。腹板的钢种为SM400低屈服钢和LY100低屈服钢。循环剪切加载试验的主要研究结果如下：低碳钢试件在加载循环开始时达到最大剪切荷载，剪切荷载能力逐渐下降到恒定剪力。这些标本的蛛网向一侧坍塌。由于材料的应变硬化，低屈服钢试件在加载循环的大剪切位移处逐渐达到恒定剪切力。这些标本的蛛网两边都坍塌了。当翼缘在非常大的剪切位移下向腹板大变形时，恒剪荷载能力降低。耗能与剪切位移成正比增加。腹板厚度越大，抗剪承载力和耗能效果越好。低屈服钢的消能效果优于低碳钢。

This report is to develop the plastic shear link concept which is applicable to the seismic-resistant dissipation of bridges. A total of twelve welded 1-section specimens is tested under cyclic shear loading. The length and height of the specimens are 2240mm and 800mm, respectively with the web thickness of 4, 5, and 7mm. The web is separated in two square panels with 800mm width by the vertical stiffeners. The width and the thickness of the flanges are 300mm and l2mm, respectively. Steel grades of the web are mild steel of SM400 and low yield steel of LY100.Followings are the main research results from the cyclic shear loading tests :The specimens made of the mild steel reach to the maximum shear load at the beginning of the loading cycles, and the shear load capacity gradually decreases to the constant shear force. The webs of these specimens collapse one side. The specimens made of the low yield steel gradually reach to the constant shear force at the large shear displacement of the loading cycles due to the strain hardening of the materials. The webs of these specimens collapse both sides. The constant shear load capacity decreases when the flanges largely deform toward the web at the extremely large shear displacement. The energy dissipation increases in proportion to the shear displacement. The thicker webs are more effective in the shear load capacity and the energy dissipation. The low yield steel is more effective than the mild steel in the energy dissipation.