双肢拼合冷弯薄壁型钢工字形截面梁受弯性能研究

Study on flexural capacity of cold-formed steel double-limb built-up I-shape beams

对6个单肢冷弯薄壁型钢C形截面梁和18个双肢拼合冷弯薄壁型钢工字形截面梁进行了受弯性能试验研究，考察梁跨高比、翼缘宽厚比、截面高宽比、螺钉连接间距以及腹板开孔对双肢拼合工字形截面梁破坏模式和极限受弯承载力的影响，验证双肢拼合截面梁受弯承载力具有“1×2≥2”的拼合效应，并采用ANSYS有限元软件进行数值模拟与影响因素分析。结果表明：试件的破坏模式为翼缘及腹板局部屈曲和畸变屈曲的相关屈曲形式。改变翼缘宽厚比和截面高宽比对双肢拼合冷弯薄壁型钢工字形截面梁的承载力影响最大，而改变螺钉连接间距（300～600mm范围内）和梁跨高比对工字形梁的承载力影响较小。在实际工程设计中，建议腹板开孔采用圆形孔洞形式，腹板开孔截面积比例取为35％～50％之间，同时腹板开孔间距应不小于400mm。在双肢拼合工字梁受弯承载力折减强度法的基础上，提出了适用于腹板开孔双肢拼合冷弯薄壁型钢工字形截面梁受弯承载力计算的强度折减修正法。

Static experiments were conducted to study the flexural performance of 6 cold-formed steel single-limb C-shape beams and 18 cold-formed steel double-limb built-up I-shape beams. The influence of span-height ratio, width-thickness ratio, height-width ratio, screw spacing and web opening size on failure modes and ultimate flexural capacity of double- limbs built-up I-shape beams are analyzed. It is verified that the flexural capacity of double-limb built-up I-shape beams was two times that of single-limb C-shape beam. Finite element software ANSYS is adopted to conduct numerical simulation and influence factors analysis. The results show that the failure modes of specimens are interactive buckling forms of local buckling and distortional buckling for flanges and webs. The width-thickness ratio and height-width ratio have a great impact on the bearing capacity of cold-formed steel double-limb built-up I-shape beams, while the screw spacing （between 300ram to 600ram） and span-height ratio have less impact. In the practical engineering design, it is recommended that the web opening form is circular hole and the web hole area ratio is between 35% and 50%. Additionally, the web hole spacing should be not less than 400ram. On the basis of strength reduction method for flexural capacity of double-limb built-up I-shape beams, the strength reduction correction method is proposed to calculate the flexural capacity of web opening cold-formed steel double-limb built-up I-shape beams.