强度减损下混凝土箱梁预应力高温损失分析  

Prestress loss of concrete bridge with box girder based on strength reduction exposed to fire

作　　者：张岗[1,2] 刘天龙[1,2] 王翠娟[3] 程海鲲 

机构地区：[1]长安大学公路学院,陕西西安710064 [2]长安大学旧桥检测与加固技术交通行业重点试验室,陕西西安710064 [3]长安大学工程机械学院,陕西西安710064

出　　处：《解放军理工大学学报（自然科学版）》2015年第4期345-352,共8页Journal of PLA University of Science and Technology(Natural Science Edition)

基　　金：国家自然科学基金资助项目(51308056);中央高校基本科研业务专项资金资助项目(2014G2210003;2013G2211004);国家留学基金资助项目(201406565013)

摘　　要：为明确火灾下混凝土桥梁预应力的衰变幅值与高温之间的变化关系,采用热力耦合计算方法,基于强度损失的虚拟层截面等效原理,设定火灾下混凝土箱梁预应力火灾高温分析工况,研究单面火灾和三面火灾模式下混凝土箱梁的截面温度场分布状况,计算不同延火时间混凝土箱梁预应力沿程(沿桥梁跨径)分布状态,揭示强度减损下混凝土箱梁预应力火灾高温沿程损失规律。研究结果表明:箱梁底板受火,温度大致呈水平层状分布;箱梁底板和两侧腹板受火,温度呈U形分布,并且多面受火时的温度峰值大于单面受火时的温度峰值;随着延火时间的增加,高温层逐渐向内扩展并且扩展宽度递增;延火全程中,相对处于腹板上部,处于腹板下部的钢束预应力沿程损失较大,四分点的预应力损失值较其他部位大,大约是其他部位的1.1倍;跨中的预应力损失增长幅度相对较大,增长幅度最大值约为9.4%;锚下预应力损失值最小;整个延火过程中,沿程预应力损失呈倒W形。To study the variation relations between the prestress decay amplitude of concrete bridges and high temperature, based on the virtualization equivalence principle of the concrete strength loss, fire conditions were designed to analyze the temperature field of concrete bridge with box girder under single-side fire and three-side fire, and the thermo-mechanics coupled method was adopted to calculate the prestress distribution along the bridge span of concrete bridges with box girder at various fire time and disclose prestress loss law of concrete bridges with box girder exposed to high temperature based on strength deroga- tion of concrete. The results show that：the temperature generally presents a layered distribution when the floor of concrete bridge with box girder is exposed to fire.When the floor and both sides of the web of concrete bridges with box girder are exposed to fire, the temperature generally presents an U-type distribution,and the temperature peak value at intersection is higher than that of in other parts.With the increase of the fire time,high temperature layer gradually extends inward and distribution width expands. Prestress loss of steel strand located at the bottom of the web is relatively more than it located in the upper position of the web,prestress loss at the quarter of span is more than that of other parts and its value is about 1.1 times than that of other parts. The increase amplitude of prestress loss at mid span is more than that of other parts,and the maximum growth rate is about 9.4%.Prestress loss loacated in anchor has a minimum value, and prestress loss along span presents an inverse W-type during various time steps. The research can provide a guideline for fire-resistant design and assessment of prestressed concerte bridge after fire hazard.

关 键 词：桥梁工程 混凝土箱梁 有限元 预应力损失 火灾 

分 类 号：U448.35[建筑科学—桥梁与隧道工程]