双肢U形拼合冷弯薄壁型钢箱梁受弯性能试验

Experimental Study on Flexural Capacity of Cold-formed Steel Double-limb U Box Beams

目的研究双肢U形拼合冷弯薄壁型钢箱梁的受弯性能,对现有拼合箱梁受弯承载力计算方法进行评估对比。方法对12根双肢U形拼合冷弯薄壁型钢箱梁进行受弯性能试验,通过分析试件破坏模式、荷载-位移曲线、荷载-应变曲线及跨中截面应力分布,考察了螺钉间距及腹板开孔对拼合箱梁破坏模式及受弯承载力的影响,并对中美规范和学者建议的拼合箱梁受弯承载力计算方法进行了验证。结果增大螺钉间距会略微降低箱梁受弯承载力;腹板开孔比为0.4时,拼合箱梁受弯承载力下降很小,当开孔比为0.7时,拼合箱梁受弯承载力和延性下降明显。拼合箱梁受弯承载力计算方法中,简单叠加法由于未考虑拼合效应,预测结果偏于保守,而《低层冷弯薄壁型钢房屋建筑技术规程》(JGJ 227—2011)中规定的方法预测结果偏大。结论双肢U形拼合冷弯薄壁型钢箱梁纯弯段破坏模式表现为局部屈曲破坏,腹板开孔较大时会显著降低拼合箱梁受弯承载力,建议实际工程中腹板开孔比不宜大于0.4;可以采用《冷弯薄壁型钢结构技术规范》(GB50018—2002)中有效宽度法计算单肢构件承载力后简单叠加近似得到拼合箱梁受弯承载力。

Built-up sections are widely used in construction industry due to the superior mechanical properties.However,there is little research about cold-formed steel double-limb box beams with web openings on the calculation method of bearing capacity.In this paper,a total of 12 build-up box beams were tested under four-point bending.By analyzing the failure mode,load-displacement curve,load-strain curve and Strain distribution of the specimen,the effects of web opening and screw spacing on the failure mode and flexural performance of the box girder were investigated.The calculation methods of flexural bearing capacity of split box girders proposed by Chinese and American codes and scholars are verified.Results show that the bending capacity of the split box girder can be significantly affected by changing the ratio of flange width to thickness and section height to width.Increasing screw spacing will slightly reduce the bending capacity of box beams.When the hole ratio is 0.4,the flexural bearing capacity of the split box girder decreases little,and when the hole ratio is 0.7,the flexural bearing capacity and ductility of the split box girder decreased significantly.Predicted results of simple superposition method are conservative because the splicing effect is not taken into account.The prediction results of the method specified in“Technical specification for low-rise cold-formed thin-walled steel buildings”(JGJ 227—2011)are relatively large.The failure mode of the double-limb U-shaped split cold-formed thin-walled steel box girder is local buckling failure,and the flexural bearing capacity of the split box girder will be significantly reduced when the web opening is large.The effective width method in“Technical code of cold-formed thin-wall steel structures”(GB50018—2002)can be used to calculate the bearing capacity of single-limb members,and then the flexural bearing capacity of the split box girder can be obtained by simple superposition and approximation.