变截面波形钢腹板-UHPC组合箱梁剪应力试验

Shear Stress Test of Non-prismatic Composite Box Girders with Corrugated Steel Webs and UHPC

为进一步减轻大跨径变截面桥梁结构自重,增加结构跨越能力并增强结构抗裂性能,提出了变截面波形钢腹板(Corrugated Steel Webs,CSW)-UHPC组合箱梁结构新理念,该结构截面尺寸更小、自重更轻,其结构剪力分布、截面剪应力分布与常规组合结构区别较大,需深入研究。以变截面CSW-UHPC组合箱梁为研究对象,取变截面微段进行受力分析,结合剪应力互等定理,推导了系统完善的腹板剪应力计算公式,并基于工程需要,提出了一种简化计算方法。继而,设计了一片大比例变截面CSW-UHPC模型梁,模拟大跨径组合梁桥施工过程中典型的受力状态,完成了不同边界条件、不同加载位置、不同加载类型及微裂缝状态共计6种工况下的静力加载试验,获得了各截面剪应力分布及沿跨度方向承剪比变化规律,并结合空间实体有限元模型对计算理论进行全面的验证。结果表明:各工况下腹板实测剪应力值与所提公式理论值、有限元结果吻合良好,证明了所提公式的正确性;组合箱梁倾斜底板参与了截面抗剪而不可忽略,体现出明显的变截面效应;特别是最大悬臂工况下其模型梁根部位置附近承剪比仅为2%~6%,剪力大部分由倾斜底板来承担,实测和理论剪应力大小为0.6~1.5 MPa,而传统公式计算值为22~24 MPa,偏差较大,说明传统等截面的剪应力计算公式已不再适用,该结构变截面效应尤为明显;钢腹板承剪情况受弯矩、剪力、轴力共同影响,弯矩、轴力的方向对腹板上剪力可能造成有利或不利的影响。

To reduce the self-weight,increase the spanning capacity of structures,and significantly improve the crack resistance of long-span non-prismatic concrete box girder bridges,the concept of a novel non-prismatic composite girder consisting of a corrugated steel web and UHPC was proposed in this study.The smaller sectional size and lighter self-weight lead to a difference between the shear force distribution of this new structure and the conventional combined structure,which needs to be studied further.Focusing on long-span non-prismatic UHPC box girders with corrugated steel webs,we used a variable section micro-segment for force analysis,combined the shear stress reciprocity theory,derived a systematic theory of corrugated steel web shear stress calculation,and proposed a simplified calculation method based on engineering needs.Subsequently,an experimental program of a large-scale variable-cross-section UHPC box girder with corrugated steel webs was performed to simulate the typical stress conditions during the construction of large-span composite girder bridges.Shear stress tests of the steel webs of the specimen under six working conditions were conducted,including different boundary constraint conditions,load positions,loading types,and nonlinear stages.The shear stress distribution of each section and bearing shear ratio along the span were obtained.Meanwhile,finite element analysis was conducted for comparison.The results showed that the test data were consistent with the theoretical and FEA results,verifying the accuracy of the theoretical formula.The inclined bottom plate of the specimen had a large proportion of shear resistance,which was not negligible and reflected the obvious variable section effect,which was affected by the bending moment,shear force,and axial force.The directions of the bending moment and axial force were different,which may cause favorable or unfavorable effects on the shear stress of the steel webs.In particular,under the maximum cantilever concentrated load condition,the shear bearing ratio of the webs near the support was only 2%-6%,the shear stress was 0.6-1.5 MPa,while the traditional formula calculation value was 22-24 MPa,with a large deviation,indicating that the traditional prismatic section shear stress calculation formula is unsuitable for non-prismatic section corrugated steel webs.The shear bearing condition of the corrugated steel web is affected by the bending moment,shear force,and axial force,and the direction of the bending moment and axial force may have favorable or unfavorable effects on the shear force on the corrugated steel web.