既有简支薄壁C形钢檩条连续化加固研究

为提高既有简支薄壁C形钢檩条的承载能力，对相邻简支C形钢檩条在支座附近采用内嵌薄壁L形钢连接成为连续檩条。对仅腹板有螺钉连接和腹板及上、下翼缘均有螺钉连接的2组加固C形钢檩条进行静力加载试验，分析了加固后檩条的破坏模态、刚度、延性、承载能力及应变发展，并与简支C形钢檩条的受力性能进行了对比。试验结果表明：加固试件的两跨檩条以整体弯曲变形为主，C形钢檩条跨中和加载处上翼缘与受压区腹板发生局部屈曲而破坏，薄壁L形钢翼缘达到屈服。简支檩条连续化加固后的承载能力、刚度均有显著提高，延性提高较小。腹板及上下翼缘均有螺钉连接加固檩条的刚度和屈服荷载提高幅度明显高于仅腹板螺钉连接加固，但两者极限荷载和延性差别较小。采用三线性钢材本构模型和壳单元，建立了同时考虑几何非线性和材料非线性的三维有限元模型进行数值模拟，计算结果与试验结果的对比验证了有限元模型的准确性。分析了不同薄壁L形钢长度对加固檩条受力性能的影响，结果表明，薄壁L形钢长度的增加对承载能力、刚度的提高幅度由大变小，刚度的提高幅度大于承载能力的提高幅度，薄壁L形钢长度宜取檩条单跨跨度的10%~15%。

Continuous reinforcement of existing simply supported cold-formed thin-walled C-shaped steel purlin

To improve the load capacity of existing simply supported cold-formed thin-walled C-shaped steel purlin, the adjacent simply supported C-shaped purlins were connected to continuous purlins by embedded thin-walled L-shaped steel near the supports. The static loading tests were carried out on the two strengthened C-shaped purlins. One purlin has screw connection only in the web and another purlin has screw connection in the web and flange. The failure mode, stiffness, ductility, bearing capacity, and strain development of the strengthened purlins were analyzed and compared with the mechanical behavior of the simply supported C-shaped purlin. The experimental results show that the global bending deformation occurs for the strengthened two-span purlin specimens. The top flange and compression web of purlins buckle near the mid-span and loading point, and the flange of the thin-walled L-shaped steel yields. The bearing capacity and stiffness of the simply supported purlins have been significantly improved after continuity, but ductility increases less. The stiffness and yield load of the strengthened purlin with screw connection in web and flange are significantly higher than that of the purlin only strengthened with screw connection in web, but the difference of ultimate load and ductility is lower. Using the trilinear steel constitutive model and shell element, a three-dimensional finite element model considering both geometric and material nonlinearity was established for the numerical simulation. The accuracy of the finite element model was validated by the comparison between calculation results and experimental results. The effects of the length of the thin-walled L-shaped steel on the mechanical behavior of the continuously strengthened purlin were analyzed. The results show that when the length of the L-shaped steel increases, the increasing extent of bearing capacity and stiffness of the reinforced purlins is decreasing. The increasing extent of the stiffness is more than that of the load capacity. 10% to 15% of the span of purlin is suitable for the length of L-shaped steel.