PC箱梁桥火灾爆炸联合作用下损伤效应研究  

Research on Damage Effects on PC Box-Girder Bridge Under Fire and Explosion

作　　者：田力[1,2] 李孟辉[1] 王剑飞 朱劲松 Tian Li;Li Menghui;Wang Jianfei;Zhu Jinsong(School of Civil Engineering,Tianjin University,Tianjin 300350,China;Key Laboratory of Coast Civil Structure Safety of Ministry of Education,Tianjin University,Tianjin 300350,China)

机构地区：[1]天津大学建筑工程学院,天津300350 [2]滨海土木工程结构与安全教育部重点实验室(天津大学),天津300350

出　　处：《天津大学学报（自然科学与工程技术版）》2024年第11期1200-1210,共11页Journal of Tianjin University：Science and Technology

基　　金：国家自然科学基金资助项目(51178310,52078333).

摘　　要：利用ANSYS/LS-DYNA建立了预应力混凝土(prestressed concrete,PC)箱梁桥三维有限元模型,采用隐式分析方法对PC箱梁桥进行单独火灾分析,得到其在不同时刻下的温度及热应力的分布特征,采用显式分析方法对PC箱梁桥进行单独爆炸分析,得到其在不同爆炸当量下的局部破坏特征以及整体位移情况.随后,对综合考虑高温和高应变率效应的混凝土本构模型和钢材本构模型进行试验验证,在得到可靠性结果的基础上对PC箱梁桥进行火灾爆炸联合作用分析.结果表明:发生桥上火灾时,桥面板的热应力重分布现象应该得到关注,桥上火灾热应力随着燃烧时间的推移,顶板和翼缘板应力下降程度要大于腹板上方混凝土应力下降程度,桥面板的热应力使得在爆炸的过程中会出现小当量炸药也能造成箱梁顶板严重局部损伤的现象.发生小当量爆炸时,若燃烧持续时间较短,材料产生的高热应力起主导作用,从而在后续爆炸过程中对顶板造成严重的局部损伤,但整体位移与常温爆炸相似;若燃烧持续时间较长,材料的高温软化效应起主导作用,顶板损伤情况有所减小,但整体位移会增大.发生大当量爆炸时,无论是材料产生的高热应力还是材料的高温软化均会造成箱梁顶板的严重破损,冲击波在箱梁的聚集作用下冲击底板与腹板交界处,最终底板坍塌.从热应力分布现象和爆炸局部破坏特征来看,单箱多室的箱梁桥可以适当提高抗爆性.The three-dimensional finite element model of a prestressed concrete(PC)box-girder bridge was established using ANSYS/LS-DYNA.An implicit analysis method was used to analyze a single fire on the PC box-girder bridge to obtain the distribution characteristics of temperature and thermal stress at different moments,while an explicit analysis method was applied to analyze a single explosion on the same bridge to obtain the local failure characteristics and overall displacement under different equivalent explosions.Then,the concrete constitutive model and steel constitutive model considering the effects of high temperature and high strain rate were experimentally verified,and the analysis of fire-explosion combined action on the PC box-girder bridge was carried out on the basis of reliable results.Results show that when a bridge fire occurs,particular attention should be paid to the redistribution of thermal stress on the bridge deck.With the passage of burning time,the thermal stress on the roof and flange plate decreases more than the concrete stress on the web,and the thermal stress on the bridge deck makes it possible that even a small amount of explosive can cause serious local damage to the roof of the box-girder in the subsequent explosion process.When a small equivalent explosion occurs while the combustion duration is short,the high thermal stress generated within the material will play a leading role and thus cause serious local damage to the roof in the subsequent explosionprocess, but the corresponding overall displacement will be similar to that in the case of a normal-temperature explosion.If the combustion duration is long, the high-temperature softening effect on the material will dominate, with areduced damage to the roof and an increased overall displacement. When a large equivalent explosion occurs, both thehigh thermal stress generated within the material and the high-temperature softening effect will cause serious damageto the roof of the box-girder. As a result, the shock wave will impact on the

关 键 词：火灾 爆炸 PC箱梁桥 有限元分析 

分 类 号：TU378.2[建筑科学—结构工程]