高强度工字钢梁腹板抗剪性能试验

Web Shear Behavior Test for High Strength I Steel Girders

为了充分利用高强钢的高强度特性,设计了4片采用Q420qD高强度腹板的焊接工字钢梁,并采用跨中单点加载的形式进行抗剪性能试验研究。分析了腹板高厚比、翼缘约束效应、剪跨比等关键参数对高强度工字钢梁抗剪性能的影响规律,研究了高强度Q420qD腹板的抗剪极限承载能力及剪切破坏机理,并验证建议理论模型的正确性与腹板抗剪承载力计算公式对高强度钢梁的适用性。研究结果表明:试验梁在腹板弹性剪切屈曲后均形成了拉力带,充分发挥了屈曲后强度,最终形成框架机构;基于试验结果确定了高强度工字钢梁腹板的拉力带分布形式与破坏框架模型,其可作为高强度工字钢梁腹板的剪切失效理论模型;采用较大的翼缘相对腹板刚度,可提供更强的剪切抗力,理论计算时应计入翼缘对腹板的约束效应,试验与理论计算的对比分析结果验证了高强度工字钢梁翼缘对腹板约束系数的合理取值应为1.25,理论模型与计算公式适用性强;随着剪跨比的增大,试验梁的腹板屈曲后强度均充分发展,但试验梁在弹性屈曲后的腹板面外变形明显减小,仅在临近剪切极限强度时腹板面外变形呈不收敛增长,因此高强度腹板设计时应兼顾腹板面外屈曲变形的控制与腹板屈曲后强度的有限利用,保证高强钢桥使用阶段的安全可靠。

To make full use of high strength character of high strength steel,4 welding I steel girders fabricated by high strength web of Q420 qD were designed and shear behavior tests were conducted by mid-span loading.Shear behavior of high strength I girders were analyzed considering parameters of web slenderness,flange restrain effect,shear span ratio,etc.The shear ultimate capacity and shear failure mechanism of high strength web of Q420 qD were analyzed,the correctness of theoretical model suggested in this paper were checked,and the equations for calculating shear capacity suitable for high strength web were testified.The results show that,firstly,the tension belt distribution form and failure frame mode are determined as shear failure theoretical model for high strength I girder web in terms of test results.Secondly,constrain effect of flange to web should be taken consider in theoretical calculation and the comparison result between test and theoretical calculation testifies that the rational value of flange constraint coefficient should be 1.25.Thirdly,the simplified theoretical equations for calculating shear strength are proposed for high strength web and the accuracy of models and theoretical equations are testified.Finally,with the increase of shear span ratio（a/hw）,the web postbuckling strength is both fully developed,but web out-plane displacement decreases obviously,and increases with misconvergence only when attaining shear ultimate strength.Thus,both web out-of-plane displacement control and post-buckling strength should be considered in balance in high strength web design,to ensure high strength steel bridge safety during service stage.