腹板开孔冷弯薄壁槽钢梁屈曲性能试验及直接强度法研究

Tests and direct strength method on buckling behavior of cold-formed thin-walled channel steel beams with web holes

为了研究腹板开孔冷弯薄壁槽钢梁的屈曲性能和完善直接强度法,对开孔数量、卷边长度不同的冷弯薄壁槽钢梁进行了纯弯试验研究,其中长卷边和短卷边试件各8个,每种卷边的试件分别在腹板开设0、1、2、3个100 mm×40 mm的矩形孔洞。试验结果表明：腹板开孔使试件破坏模式从单一的畸变屈曲或局部屈曲变为以畸变屈曲为主的畸变-局部相关屈曲或以局部屈曲为主的局部-畸变相关屈曲;与未开孔钢梁相比,开孔钢梁的承载力有所降低,但开孔数量对钢梁承载力影响不大。采用ANSYS有限元程序对试验进行了模拟,模拟结果与试验结果吻合良好,验证了有限元分析此类开孔构件的可行性。进而开展了有限元参数分析,验证了基于折减腹板厚度法利用有限条程序CUFSM求解腹板开孔冷弯薄壁槽钢梁弹性畸变屈曲临界应力的准确性,并对此类构件的弹性局部屈曲临界应力计算公式进行了修正。基于腹板开孔冷弯薄壁槽钢梁的试验结果、有限元分析结果以及弹性屈曲临界应力求解方法,得到了此类构件在以畸变屈曲为主和以局部屈曲为主破坏模式下的直接强度法修正公式。

In order to investigate the buckling behavior of cold-formed thin-walled channel steel beams with web holes and to develop the direct strength method for such beams, cold-formed thin-walled channel steel beams with different numbers of web holes and different widths of edge stiffeners were tested under pure bending. There were eight specimens with long-edge stiffeners and eight specimens with short-edge stiffeners. Each specimen had 0, 1, 2 or 3 rectangle holes, all with dimensions of 100 mm × 40 mm, on the web. It is shown that the web holes change the failure modes of the specimens from only distortional buckling or only local buckling to combined distortional-local buckling controlled by distortional buckling or local buckling. Compared with the specimens without holes, the bending strengths of the specimens with holes decreased slightly, but the number of web holes had little effect on the bending strength. The tests were simulated using the finite element software ANSYS, and the simulation results show good agreement with the test results, demonstrating the feasibility of using the finite element method to analyze this kind of specimens. Furthermore, the finite element model was used to conduct parameter analyses, which demonstrates the accuracy of solving the elastic distortional buckling critical stress using the CUFSM finite strip program based on the discounted-thickness method. The formula for calculating the elastic local buckling critical stress was revised for flexural members with holes. The calculation method of elastic buckling critical stress was used together with the experimental results and the results from the finite element analysis to establish the revised direct strength method formulas for the failure mode controlled by distortional buckling and that controlled by local buckling, resoectivelv.