CU型双肢拼合CFS箱梁屈曲机制与受弯承载力计算方法

Buckling mechanism and bearing capacity calculation method of CU type CFS built-up double-limb box girder

通过静力试验、有限元模拟与理论分析,研究了CU型双肢拼合CFS箱梁翼缘板与腹板局部屈曲的耦合机制,分析了螺钉间距和加劲肋数量等对屈曲机制和承载力的影响,得到了CU型双肢拼合CFS箱梁受弯承载力的简化计算方法。研究结果表明:CU型双肢拼合CFS箱梁的整体失效机制为局部屈曲;螺钉间距较大(200、300 mm)时,翼缘板先于腹板屈曲,降低了对腹板的侧向约束,引起腹板屈曲与构件失效;螺钉间距较小(100 mm)时,腹板先于翼缘板屈曲,拼合箱梁承载力较高;螺钉间距每减少100 mm,CU型双肢拼合CFS箱梁受弯承载力可提高2.8%,但延性没有显著变化;设置加劲肋可直接增强腹板屈曲性能,提高拼合箱梁受弯承载力与延性;在纯弯段每增设1个加劲肋,CU型双肢拼合CFS箱梁受弯承载力可提高10%。建立了模拟上翼缘对腹板约束的弹性支承模型,基于广义变分原理和弹性板壳理论,推导了三边简支、一边弹性支承的腹板弹性临界屈曲应力,得到了用于计算CU型双肢拼合CFS箱梁受弯承载力的修正直接强度法,并与已有研究试验数据以及GB 50018—2002和AISI S100-16的计算结果进行对比,验证了修正公式的合理性。修正直接强度法平均相对误差绝对值为7.86%,修正的计算式可用于CU型双肢拼合CFS箱梁在局部屈曲控制下的受弯承载力计算。

The interaction of local buckling between flange and web,and the influence of screw space and stiffener numbers on the buckling mechanism and bearing capacity of CU type CFS double-limb box girder were studied by means of specimen loading tests,finite element method,and the theoretical analysis method.A simplified method for calculating the moment capacity of the CU type box girder was obtained.The research results show that the failure mechanism of CU type double-limb box girder is local buckling.When the screw space is large(200 mm and 300 mm),the flange buckles before the buckling of the web thus reducing the lateral restraint on the web.When the screw space is small(100 mm),the web plate buckles before the buckling of the flange and the bearing capacity of the girder is improved.When the screw space decreases by 100 mm,the bearing capacity of the girder increases by 2.8%,while the ductility does not change significantly.Setting stiffeners can improve the web buckling performance and increase the bearing capacity by 10%and improve the ductility of the girder as well.An elastic support model was proposed to simulate the constraint of flange to web.Based on the finite element analysis,together with generalized variational principle and the elastic plate theory,the elastic critical buckling stress of the web was derived.A modified direct strength method for the moment capacity of CU type CFS double-limb box girder was obtaind and its applicability was verified by the comparison with available test results by other researchers,as well as the prediction by GB 50018—2002 and AISI S100-16.The absolute value of average relative error of modified strength method is 7.86%.It can be used to calculate the flexural capacity of CU type CFS double-limb box girder under local buckling control.