PC梁桥结构的钢绞线张拉问题及补救措施分析

发布时间：2018-05-21 04:19

本文选题：预应力混凝土梁桥 + 钢绞线张拉　；参考：《公路工程》2017年02期

【摘要】：以一座预应力混凝土斜梁桥和一座预应力混凝土弯梁桥的钢绞线张拉施工问题为例,针对张拉过程中出现的锚具回缩有效预应力损失、伸长量偏小力筋超张拉的问题,采用有限元数软件建立两座大桥的分析模型,详细考虑钢绞线现场施工状态,分析张拉施工问题对梁体结构的影响。分析表明:预应力混凝土斜梁施工过程中预应力筋伸长量小的问题可通过增大锚下控制应力改善,且对该现浇箱梁桥影响很小,结构在施工期间和设计规范确定的正常运营状态下是安全的,由于超张拉使用阶段预应力束的拉应力超过0.65fpk,但后续个别预应力束张拉控制应力按照不大于0.80fpk继续施工可行;预应力混凝土弯梁桥顶板4根负弯矩束的回缩对桥梁结构的正常使用极限状态有影响,造成斜截面抗裂验算超限,钢束的回缩使得这部分预应力筋的有效预应力减小甚至失效,造成该部位箱梁顶面最大主拉应力超过规范限值,可采取增加负弯矩区的有效预应力方式补救。
[Abstract]:Taking the construction of a prestressed concrete skew beam bridge and a prestressed concrete curved beam bridge as an example, aiming at the problems of the effective prestressing loss of Anchorage in the process of tensioning and the over-tensioning of the extended-tensioning tendons, a prestressed concrete skew beam bridge and a prestressed concrete curved beam bridge are taken as an example. The finite element software is used to establish the analysis model of two bridges. The construction state of steel strand is considered in detail, and the influence of tensioning construction on the beam structure is analyzed. The analysis shows that the small extension of prestressed tendons in the construction of prestressed concrete skew beam can be improved by increasing the stress under the anchor, and has little effect on the cast-in-place box girder bridge. The structure is safe during construction and in the normal operation state determined by the design code. The tensile stress of the prestressing beam in the stage of overtensioning is more than 0.65 fpk. however, it is feasible to continue the construction under the condition of no more than 0.80fpk. The retraction of four negative moment beams on the roof of prestressed concrete curved beam bridge has an effect on the normal service limit state of the bridge structure, which results in the over-limit of the anti-cracking calculation of the inclined section, and the reduction of the steel beam makes the effective prestress of this part of prestressed tendons decrease or even fail. The maximum principal tensile stress of the top surface of the box girder exceeds the limit value of the code, which can be remedied by increasing the effective prestressing force in the negative bending moment region.
【作者单位】：郑州大学土木工程学院;
【基金】：2016年度河南省基础与前沿技术研究项目(162300410264)
【分类号】：U445.57

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