型钢-UHPC轻型组合桥面板及其抗弯性能研究

Research on flexural performance of section steel-UHPC lightweight composite bridge deck

正交异性钢桥面是目前800m以上国内外特大跨径钢桥的唯一选择,主因是自重轻、强度高、架设方便。但其存在疲劳开裂风险大、运维成本高的缺点。随着高性能材料UHPC的研发和应用,为构建自重轻、病害少、经济性好的桥面新结构提供了可能性。经过多年研究,作者提出一种新型桥面板结构——型钢-UHPC轻型组合桥面结构,将型钢、钢板条与UHPC组合,桥面板的形成无任何板件焊接,因而具有高抗疲劳性,且与传统钢桥面相比,自重持平、造价减半,可作为除“正交异性钢桥面”外的“第二种”大跨径钢桥的桥面结构方案。该文研究这种轻型组合桥面板预制板及横向接缝的抗弯性能,制作4个条带模型(包括2个预制板试件和2个接缝试件),开展三点弯曲的横向接缝负弯矩试验和预制板正弯矩试验,并对试验结果进行分析;基于“条带法”建立预制板试件极限承载力计算模型,提出接缝试件的UHPC开裂名义拉应力计算方法;基于某斜拉桥应用实例,进行整体计算和局部计算,验证新型组合桥面结构在实桥上应用的可行性。研究结果表明:(1)型钢与UHPC间在极限状态前相对滑移非常小,具有良好的协同受力性能;(2)预制板试件的正弯矩极限承载力以型钢屈服控制,而接缝试件负弯矩极限承载力以UHPC开裂和加密钢筋断裂控制;(3)接缝试件的“T形”接缝、加密钢筋、燕尾形的企口、交错式切割型钢钢条等构造设计对接缝整体抗弯拉性能有很好的提高效果;(4)预制板试件极限承载力计算模型所得计算值与试验值吻合良好,该模型搭配名义拉应力计算方法,可帮助工程实际问题的设计与应用;(5)试验结果与实桥的有限元计算值相比,新型桥面结构均有1.3倍以上的安全系数,新型组合桥面应用于实桥具有可行性。

The orthotropic steel bridge deck is currently the only option for mega-span steel bridges over 800m,mainly due to its lightweight,high strength and ease of erection.However,it has the disadvantages of a high risk of fatigue cracking and high costs of operation and maintenance.With the development and application of the high-performance material UHPC,it offers the possibility to build a new structure for bridge decks with lighter dead weight,fewer defects and better economy.Over the years of research,the authors have proposed a new deck structure-the Section steel-UHPC lightweight composite bridge deck,which combines section steel,steel plate strips and UHPC.It could be the“second”large span steel bridge deck structure,in addition to the“orthotropic anisotropic steel deck”.In this work,the flexural performance of the prefabricated slabs and transverse joints of this lightweight composite deck was studied.The calculation model for ultimate bearing capacity of the prefabricated slab specimen was established based on the“strip method”,and a method for calculating the UHPC nominal tensile stress of the joint specimen was proposed.Based on the application scheme of a cable-stayed bridge,the whole and local calculations were carried out to verify the feasibility of the new composite deck structure on the real bridge.The results indicate that:(1)The relative slip between the section steel and UHPC is very small before the ultimate state,and the section steel and UHPC can work collaboratively;(2)The ultimate bearing capacity of positive moment of the prefabricated slab specimen is controlled by the yielding of the section steel,while the ultimate bearing capacity of negative moment of the joint specimen is controlled by the cracking of the UHPC and the fracture of the additional rebars;(3)The“T-shaped”joints,additional rebars,dovetailshaped groove,staggered cutting section steel bars and other structural designs of joint specimens shall be beneficial to the flexural performance of joint;(4)The calculated values from the ultimate bearing capacity calculation model of the prefabricated slab specimen are in good agreement with the test values,and the model,along with the nominal tensile stress calculation method,shall be helpful in the design and application of practical engineering problems;(5)Compared to the finite element calculations of the real bridge,the test results show that the new deck structure has a safety factor of more than 1.3 times,making it feasible to apply the new composite bridge deck to the real bridge.