PC梁桥结构的钢绞线张拉问题及补救措施分析  

Analysis of Steel Strand Tension Construction Problem and Remedial Measure for PC Beam Bridge Structure

作　　者：李杰[1] 李娜[1] 

机构地区：[1]郑州大学土木工程学院,河南郑州450001

出　　处：《公路工程》2017年第2期91-96,102,共7页Highway Engineering

基　　金：2016年度河南省基础与前沿技术研究项目(162300410264)

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。Taking construction problem of steel strand tension of a prestressed concrete skew girder bridge and curved girder bridge as example, aiming at the problems of effective prestressing loss because of anchorage retraction and over tensioning because of small elongation, using finite element soft- ware to build two bridges＇ analysis model, considering the construction state of the steel strand in detail, the problems of impact to beam＇ s safe is analyzed. It is indicated that over tensioning may improve small elongation of the steel strand. And the step＇ s influence is very small to the box girder bridge. Structure is safe during construction and normal operation. But because of the extra tension, the steel strand＇ s tensile stress is not satisfied with the design specification and exceeds 0. 65fpk. Then the later tension control stress is not greater than 0. 80 fpk to continue the construction. The 4 negative moment steel strands is affected to the curved girder bridge ＇ s serviceability limit state. And the skew section crack check does not meet the requirements. The retraction of the steel strand causes the effective prestressing of this part to be reduced or even failed. The maximum principal tensile stress of the box girder is more than the standard limit. Increasing the effective prestressing method of the negative moment zone may remedy.

关 键 词：预应力混凝土梁桥 钢绞线张拉 钢束回缩 超张拉 

分 类 号：U448.215[建筑科学—桥梁与隧道工程]