大跨度铁路钢-混组合梁负弯矩区桥面板抗裂措施研究

Research on Anti-Cracking Measures for Deck Panels in Hogging Moment Zone of Long-Span Steel-Concrete Composite Girder Railway Bridge

为研究铁路荷载作用下大跨度钢-混组合梁负弯矩区桥面板开裂情况及抗裂技术,以某主跨168 m的铁路钢-混组合连续刚构桥为背景,采用MIDAS Civil软件对桥面板受力情况进行建模分析,并开展抗拔不抗剪连接件技术及预应力技术对桥面板抗裂性能影响的研究,结合抗裂措施工作原理及施工可行性,提出适用于减小负弯矩区桥面板裂缝宽度的实施方案。结果表明:采用普通栓钉连接、桥面板常规配筋条件下的钢-混组合梁,运营阶段主力及主力+附加力工况下负弯矩区桥面板裂缝宽度均不满足规范要求;墩顶处桥面板与0号块固结及非固结2种形式下,抗拔不抗剪连接件桥面板抗裂方案均不适用,抗拔不抗剪连接件的适应性受桥面板与0号块连接构造及桥面板整体与钢桁架上弦杆顶面连接形式影响较大;对桥面板配置纵向预应力筋能有效降低拉应力水平,设后浇带预应力筋张拉方案负弯矩区桥面板最大拉应力较桥面板浇筑成型后张拉预应力筋方案更低,更能充分发挥预应力效应,且便于工程实施,建议工程应用中宜控制湿接缝占比小于10%,预应力筋锚固断面拉应力突变值宜控制在2 MPa以内。

This paper focuses on the cracking behaviors of deck panels in the hogging moment zones of the long-span steel-concrete composite girder bridge under rail loads.A steel-concrete composite continuous rigid-frame bridge owning a main span of 168 m and accommodating rail traffic was used as a case.The mechanical properties of the deck panels were simulated in MIDAS Civil,and the effects of the uplift-restricted and shear-free connecting technology and prestress technology on the anti-cracking performance of the deck panels were analyzed.Considering the mechanism and constructability of the anti-cracking measures,a cracking remedial plan was worked out,aiming to reduce the crack widths of deck panels in the hogging moment zone.As per the analysis,for the composite girder in which the steel girders and concrete panels are connected via common studs and the deck panels are fitted with common reinforcement,the crack widths of deck panels in the hogging moment zone under the action of primary and additional forces at the service stage do not meet the code requirements.The uplift-restricted and shear-free connectors are neither applicable to the composite girder where the pier-top concrete panels are fixed with the pier-top steel girder segment nor the composite girder where the pier-top concrete panels are not fixed with the pier-top steel girder segment,which are sensitive to the connection of the concrete panels and the pier-top steel girder segment as well as the connection between the overall concrete panels and the top surface of upper chords of the steel trusses.Adding longitudinal reinforcement can effectively reduce the tensile stresses in the deck panels,the maximum tensile stresses in the deck panels in the hogging moment zone of the composite girder with cast-in-place stitches are lower than the composite girder with prestressing tendons tensioned after the casting of deck panels,which allows the full play of the prestress effects,and is easy to be implemented.It is suggested to control the cast-in-place stitches less than 10%and the abrupt variation of the tensile stress in the anchor section of the prestressing tendons less than 2 MPa.