基于后结合法的钢-混组合连续梁桥负弯矩区阻裂方法

Crack Resistance Method of Negative Bending Moment Region for Steel-Concrete Composite Continuous Beam Bridge Based on Post-combination Method

目的对钢-混组合连续梁桥在负弯矩区的不利受力形式进行抗裂优化分析,提出一种通过特殊布置的剪力连接方式延缓负弯矩区钢梁与混凝土桥面板组合时间的方法即后结合分析法,改善组合梁桥面板开裂问题。方法以一座(40+50+40)m钢-混组合连续梁桥为例,利用有限元软件建立全桥梁单元模型,将改进的后结合法与预压法、支座位移法及部分预应力法等常规方法进行比较分析,对比负弯矩区成桥阶段混凝土桥面板应力值、不同措施下应力储备情况、开裂弯矩及最大裂缝宽度。结果后结合法对于组合连续梁负弯矩区的改善效果明显,相同配筋下应力储备为5.76 MPa,是部分预应力法的1.56倍、预压法压重500 kg/m^(2)的4.8倍、支座位移法顶升20 cm的2.1倍;开裂弯矩较之预压法、支座位移法等有显著提升,运营阶段中支点处最大裂缝宽度仅为0.08 mm。结论部分预应力法应力储备不足;预压法及支座位移法应力储备值较小抗裂效果不明显,更适合用于中小跨径桥梁中,或作为预防开裂的辅助措施,与其他措施配合使用;后结合技术对于组合连续梁负弯矩区处理效果最优,可在大跨度或重载组合连续梁桥中采用。

In order to improve the cracking of steel-concrete composite beam bridge deck,the anti-cracking optimization analysis of the steel-concrete composite continuous beam bridge with the unfavorable stress forms in the negative bending moment region is carried out.And a new method of delaying the combination time in the negative bending moment region between the steel beam and the concrete bridge deck by the special arrangement of shear connection is studied,namely the post-combination analysis method.A(40+50+40)m steel-concrete composite continuous girder bridge taken as an example,the whole bridge element model is established by the finite element software.And the improved post-combination method is compared with the conventional methods such as preloading method,bearing displacement method and partial prestress method.The stress value of concrete bridge deck slab,stress reserve under different measures,cracking moment and maximum crack width in the negative moment area with the method mentioned above are compared.Under the same reinforcement,the stress reserve is 5.76 MPa,which is 1.56 times that of the partial prestressing method,4.8 times that of the preloading method with compress weigh 500 kg/m^(2),and 2.1 times that of the bearing displacement method with support 20 cm.The cracking moment is significantly improved compared with other methods,and the maximum crack width at the fulcrum in the bridge operation stage is only 0.08 mm.The prestress applied by the partial prestress method is not efficient;The stress reserve value of preloading method and bearing displacement method is small,and the anti-cracking effect is not obvious,which is more suitable for medium and small span bridges,or as an auxiliary measure to prevent cracking,combined with other measures;The post-combination technology has the best treatment effect on the negative bending moment area of composite continuous beam,and it is recommended to be used in large span or heavy load composite continuous beam bridges.