摘要
为了解大尺寸预应力UHPC箱梁的抗弯性能,以预应力UHPC公路桥——河北石磁跨线桥为背景,设计、制作1片长30 m的足尺预应力UHPC箱梁模型进行四点弯曲试验,结合有限元计算结果,分析试验现象及裂缝分布、跨中荷载~位移曲线、受拉区UHPC及筋材应力~应变曲线。在此基础上分别考虑普通钢筋配筋情况、预应力筋数、腹板厚度和底板厚度等参数对预应力UHPC箱梁进行结构优化设计研究。结果表明:箱梁破坏时受压区UHPC未压溃、受拉区钢纤维被拔出,裂缝贯通底板;根据荷载~位移曲线,箱梁受力可分为弹性阶段、裂缝发展阶段、裂缝快速发展阶段和破坏阶段;根据应力~应变曲线,受拉区UHPC在纵筋屈服时仍能贡献抗拉能力;试验现象及力学指标实测值均说明了预应力UHPC箱梁抗弯能力还有很大富裕空间,可进一步优化。完全不配置普通钢筋的预应力UHPC箱梁仍能满足抗弯承载能力极限状态设计要求;底部预应力筋数增多可有效提高受压区UHPC的抗压强度利用率;腹板厚度过薄会造成腹板主拉应力过大问题,不宜薄于8 cm;采用体外预应力的方法可有效减薄底板所需厚度。
This study investigates the flexural behavior of the large prestressed UHPC box girder.An overpass carrying a section of the Shijiazhuang-Ci County Expressway in Hebei Province is used as a case.A 30 m-long full-scale prestressed UHPC box girder mock-up was prepared for the four-point flextural tests,together with the finite element calculation,the findings of the tests as well as multiple key factors were analyzed,including crack distribution,midspan load-dispalcement curve,UHPC in tensile zone,and the stress-strain curves of the tendons.In the flexural tests,the UHPC in the compressive zone was not crushed when the box girder fractured,the steel fibers were pulled out in the tensile zone,and the cracks propagated through the bottom slabs of the box girder.The load-displacement curves indicate that the box girder experienced four stages during the test,including the elastic stage,the crack propagation stage,the crack rapid propagation stage and failure stage.It can be seen from the stress-strain curves that the UHPC in the tensile zone still contributes tensile stress even when the longitudinal tendons were yielded.The findings in the flexural tests and the measured mechanical property indexes all proved that there was large flexural performance margin of the prestressed UHPC,which can be further optimized.The optimization of the prestressed UHPC box girder was performed considering the amount of common reinforcing bars,prestressing tenons amount,web thickness and bottom slab thickness.It is shown that the UHPC box gider with no normal reinforcement still meets the design requirements of ultimate limit state.Increasing the number of prestressing tendons in the bottom slabs can effectively enhance the compressive strength utilization rate of the UHPC in compression zones.The web thickness should be kept within proper range,thinner webs are more likely to succumb to oversized principal tensile stress,thus better being no less than 8 cm.Adding external prestressing tendons are associated with the reduction of the t
作者
马熙伦
唐梓轩
陈宝春
范冰辉
MA Xilun;TANG Zixuan;CHEN Baochun;FAN Binghui(School of Civil and Hydraulic Engineering,Ningxia University,Yinchuan 750021,China;College of Civil Engineering,Fuzhou University,Fuzhou 350108,China)
出处
《桥梁建设》
EI
CSCD
北大核心
2024年第3期93-99,共7页
Bridge Construction
基金
国家自然科学基金项目(52368025)
宁夏自然科学基金项目(2023AAC03131)~~。
关键词
预应力UHPC箱梁
抗弯性能
破坏形态
裂缝分布
结构优化
足尺模型试验
有限元法
prestressed UHPC box girder
flexural behavior
failure mode
crack distribution
structural optimization
full-scale model test
finite element method
