采用后张预制板技术的组合梁负弯矩段长期抗裂性能研究

RESEARCH ON LONG-TERM CRACKING RESISTANCE OF NEGATIVE MOMENT SECTION IN COMPOSITE BEAM USING POST-TENSIONED PRECAST SLAB TECHNOLOGY

  • 摘要: 组合梁负弯矩区在受拉的不利作用下容易出现混凝土开裂、挠度过大等病害,混凝土长期收缩徐变作用会进一步加重这些病害,严重影响组合梁桥的受力性能。该文提出一种后张预制板抗裂技术,在考虑收缩徐变作用的情况下,基于依托案例进行有限元数值模拟分析,验证该技术的有效性。为考虑收缩徐变作用,该文基于AAEM法的收缩徐变计算原理,编写了适用于ABAQUS显/隐式的时变效应程序,并基于组合梁长期试验验证时变效应程序及有限元建模方法的可行性。研究结果表明:基于AAEM法编写的收缩徐变预测模型及有限元建模方法有较好的适用性,与试验结果较为吻合,误差较小;后张预制板抗裂技术有效降低了因收缩徐变引起的挠度增加、预应力损失,提高了桥梁受力性能。该文可为组合梁负弯矩区开裂问题提供技术参考,也为有限元模拟考虑收缩徐变效应提供一定理论基础。

     

    Abstract: In the negative moment section of composite beams, concrete cracking and excessive deflections are easy to occur under the adverse conditions of tensioning. The long-term shrinkage and creep of concrete further aggravate these diseases and seriously affect the mechanical performance. In this study, an anti-cracking technology for post-tensioned precast slabs is proposed. The technology proposed is verified by numerical analysis upon a case study. In order to take into account the shrinkage and creep effect, an explicit/implicit time-varying effect program for ABAQUS is developed upon the AAEM algorithm of shrinkage and creep principle. The program of the time-varying effect and the finite element modeling is verified upon long-term experiments of composite beams. Results show that: The compiled prediction model of shrinkage and creep upon the AAEM method and modeling are effective, and identical to the experimental results with small error; The anti-cracking technology of post-tensioned prefabricated slab can effectively reduce the deflection and prestressing loss caused by shrinkage and creep; and improve the performance of the bridge. The study can provide a technical reference for cracking of negative moment section in composite beams and, a theoretical basis for finite element analysis considering the shrinkage and creep.

     

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