7075-T6高强铝合金受弯构件局部稳定试验研究

Experimental Study on Local Buckling Behavior of 7075-T6 High-Strength Aluminum Alloy Beams

为研究结构工程中高强铝合金受弯构件的局部稳定性能,促进高强铝合金的实际应用,本文针对7个7075-T6铝合金工字形截面梁开展了局部稳定试验研究,包括4个弯剪加载试件和3个局部承压试件,并测量了7075-T6铝合金的材料力学性能和试件的初始局部几何缺陷,重点分析了试件的破坏形态、极限承载力、局部屈曲承载力和荷载-跨中竖向位移曲线.试验结果表明:7075-T6铝合金材料平均名义屈服强度可达约497 MPa,试件翼缘与腹板的平均初始局部几何缺陷幅值百分比分别为0.40%和0.10%.试验中4个弯剪加载试件发生弯剪屈曲破坏,形成拉力带;3个局部承压试件发生腹板局部屈曲破坏,腹板出现明显凸起.采用应变反转法确定了构件的局部屈曲荷载,发现构件的截面利用率和屈曲时应力水平均随着腹板高厚比的增大而降低.跨中加劲肋的布置能大幅度提高构件的承载力和延性.同时,根据试验得到的极限承载力结果,对比了现行欧洲规范(EN 1999-1-1:2007 Eurocode 9)、美国规范(Aluminum Design Manual 2020)和中国规范(GB 50429—2007)中设计方法的计算值,3个规范计算值与试验结果的平均比值分别为0.717、0.682和0.498,表明上述规范预测7075-T6高强铝合金工字形截面受弯构件在腹板屈曲情况下试件的极限承载力偏于保守,其中欧洲规范的预测结果更为准确.

To study the local buckling behavior of high-strength aluminum alloy beams in structural engineering and promote the actual applications of high-strength aluminum alloy,local buckling tests were carried out on seven 7075-T6 aluminum alloy H-section beams,including four specimens with mid-span stiffeners and three specimens without mid-span stiffeners.The material and mechanical properties of 7075-T6 aluminum alloy and the initial local geometric imperfections of specimens were measured,and the failure modes,ultimate loads,critical local buckling loads and load-vertical displacement curves for specimens at mid-span were analyzed in detail.Test results indicated that the average nominal yield strength of 7075-T6 aluminum alloy reached approximately 497 MPa,and the mean values of initial local geometric imperfection amplitude ratios of flanges and webs were 0.40%and 0.10%,respectively.The four specimens with mid-span stiffeners failed by shear buckling,and a tension field was formed.In comparison,the three specimens without mid-span stiffeners failed by web crippling,and the web of them bulged.The critical local buckling loads were determined using a strain reversal method,and it was found that both the ratio of section utilization and the stress level during buckling decreased with an increase in the ratio of width-to-thickness of the web.The layout of mid-span stiffeners can greatly improve the ultimate loads and ductility of members.In addition,test results were utilized to compare the ultimate loads of bending members calculated by design methods proposed in the existing European standard(EN 1999-1-1:2007 Eurocode 9),American standard(Aluminum Design Manual 2020)and Chinese standard(GB 50429—2007).The mean values of ratios of results calculated using the three standards to test results were 0.717,0.682 and 0.498,respectively,indicating that the three standards offer conservative predictions while the European standard provides the most accurate prediction.