负载下钢结构工字形压弯构件焊接加固试验

Experimental study on I section steel beam-columns strengthened by welding while under load

为研究钢结构压弯构件在负载下焊接加固过程的热影响以及不同初始负载对焊接加固后受力特性的影响,进行了压弯钢柱的静力试验.被加固钢柱均为工字形双轴对称截面,置于顶端面内自由面外平动约束、底端固接的边界条件下,柱顶固定面内偏心距按四档不同初始负载分别进行.采用翼缘外对称贴焊钢板加固方案,材料类型均为Q345B级普通碳素钢.研究了负载下焊接加固过程构件的位移变化、腹板焊接应力应变重分布、加固后失稳破坏模式及稳定承载力.结果表明:加固焊接次序决定了焊接残余变形及焊接应变重分布的发展机理;初始负载影响焊接残余变形大小;而焊接热输入和初始负载大小共同影响荷载-位移曲线的焊接平台段宽.较小的初始负载几乎不影响承载力,而较大的初始负载明显对承载力不利.此外,初始几何缺陷也影响加固后承载力.

The static test of steel beam-columns was conducted to investigate the heat effect during process of welding strengthening while under initial load and the influence of different initial load on load-carrying behavior after welding reinforcement. The biaxial-symmetry I section columns were placed under boundary conditions that top of column was movable in plane while displacement constrained out plane and bottom of column was totally constrained. Therein 4 classes of initial loads were separately applied to the top of columns at a fixed in-plane eccentricity. Strengthening scheme was selected by symmetrically welding steel plates to outside surfaces of flanges, and grade of steel was carbon steel type Q345B. The displacement changes of specimen and welding stress and strain distribution of web were discussed during welding strengthening while under load, as well as the buckling mode and stability bearing capacity after strengthening. The results show that welding strengthening procedure decides the development mechanism of welding residual deformation and strain distribution. Initial load affects the magnitude of welding residual deformation while heat input and initial load coeffect the plateau length of load- displacement curve. Lower initial load has little influence on capacity while higher initial load obviously reduces capacity. Besides, the initial geometric imperfections also impact capacity after strengthening.