混凝土梁桥过火后预应力损失  

The prestressing loss of concrete beams after exposed to fire

作　　者：郝朝伟 张悦杉 王明法 陈彦江[3] HAO Chaowei;ZHANG Yueshan;WANG Mingfa;CHEN Yanjiang(Research Institute of Highway,Ministry of Transport,Beijing 100088,P.R.China;Construction Management Branch of Shandong Expressway Group Co.,Ltd.,Jinan 250001,P.R.China;Beijing Laboratory of Earthquake Engineering and Structural,Beijing University of Technology,Beijing 100124,P.R.China)

机构地区：[1]交通运输部公路科学研究所,北京100088 [2]山东高速集团有限公司建设管理分公司,济南250001 [3]北京工业大学工程抗震与结构诊治北京市重点实验室,北京100124

出　　处：《重庆大学学报》2022年第11期25-33,45,共10页Journal of Chongqing University

基　　金：国家自然科学基金资助项目(51608238);山东省交通运输科技项目(2017B62)。

摘　　要：火灾中产生的高温对预应力结构有较大影响,因降低结构的有效预应力,导致过火后受拉外缘压应力储备降低,结构提前开裂,影响结构使用性能和耐久性。为快速确定预应力混凝土梁过火后的有效预应力,以某省过火后拆除的32片梁为样本,通过实测过火后混凝土梁桥钢绞线永存应力,获得剥落深度比与预应力损失比的回归公式,选用极限承载能力试验及有限元数值分析验证该公式的适用性。结果表明,火灾后梁板预应力钢束出现应力损失,当混凝土剥落深度超过1/3钢绞线净保护层时,预应力损失不可忽略;先张法预应力混凝土结构,抗火设计应适当提高钢绞线保护层厚度;当混凝土剥落深度超过2/3钢绞线净保护层时,预应力损失率达10%,严重影响结构刚度。The high temperature produced in fire has a great influence on the pretensioned pre-stressed concrete beams.Due to the decrease of the effective prestressing force in the structure,the compressive stress spread over edge girth in tension is reduced,and structural cracks appear early,resulting in the decrease of service performance and durability.To detect the effective prestressing force of the pre-stressed concrete beams exposed to fire quickly,thirty-two pieces of beams exposed to fire were taken as samples.The regression formula of spalling depth ratio and prestress loss ratio was obtained by measuring the permanent stress of steel strand of concrete girder bridge after exposed to fire,and the applicability of the formula was verified by an experimental and finite element analysis on ultimate bearing capacity.The results show that the phenomenon of prestress loss of beam prestressed steel bundle exists.When the spalling depth of concrete exceeds 1/3 of the net protective layer of steel strand,the prestress loss cannot be ignored.The thickness of the steel strand protective layer should be increased appropriately for pretensioned prestressed concrete structures in fire resistance design.When the spalling depth of concrete exceeds 2/3 of the net protective layer of steel strand,the rate of prestressing loss due to high-temperature creep exceeds 10%,resulting in severe decrease of the girder stiffness.

关 键 词：桥梁工程 空心板 预应力 火灾 

分 类 号：U442.55[建筑科学—桥梁与隧道工程] U445.7[交通运输工程—道路与铁道工程]