桥塔附近油罐车火灾和爆炸联合作用下斜拉桥动力响应

Dynamic response of cable-stayed bridge under combined effect of fire and explosion of tank truck nearby pylon

首先,利用ANSYS/LS-DYNA有限元软件建立了一座双塔钢斜拉桥三维空间有限元模型,分析了桥塔附近油罐车火灾单独作用下斜拉桥的温度分布特征和结构响应;其次,验证了综合考虑高温软化效应和高应变率效应的钢材本构模型可靠性,分析了桥塔附近火灾和爆炸联合作用下斜拉桥关键构件的局部破坏特征和桥梁整体位移响应;第三,研究了燃烧时间和爆炸当量对桥塔在火灾下抗爆性能的影响;最后,分析了桥塔在火灾和爆炸联合作用下的倒塌过程。研究结果表明:由于热膨胀效应,火灾在短时间内便可导致桥塔等受压构件的应力迅速增大;火灾初期,桥塔受火侧产生远离火灾方向的侧向位移,随着火灾继续发展,桥塔受火侧的承载力逐渐下降,桥塔受火侧的侧向位移逐渐向火灾方向发展,最大达到了0.21 m;火灾燃烧时间越长或爆炸当量越大,桥塔在火灾爆炸作用下产生的局部破坏越严重;合理布置横隔板可有效提高桥塔的抗爆性能;火灾和爆炸联合作用下,桥塔整体产生朝向爆炸源方向的侧向位移,随着燃烧时间延长,桥塔在爆炸荷载下产生的侧向位移逐渐增大。

Firstly,a three-dimensional finite element model of a steel cable-stayed bridge with double pylon was established by using ANSYS/LS-DYNA finite element software.The temperature distribution characteristics and structural response of the cable-stayed bridge with the fire of tank truck nearby the pylon were analyzed.Secondly,the reliability of the steel constitutive model considering high temperature softening effect and high strain rate effect was verified.The local failure characteristics of the key components of the cable-stayed bridge and the overall displacement response of the bridge with fire and explosion nearby the pylon were analyzed.Thirdly,the influence of combustion time and explosion equivalent on the explosion resistance of the pylon with fire was studied.Finally,the collapse process of the pylon with fire and explosion was analyzed.The results show that due to the thermal expansion effect,fire can lead to a rapid increase in the stress of compression members,such as pylons in a short time.In the early stage of fire,the lateral displacement of the fire side of the pylon is far away from the fire direction.With the development of the fire,the bearing capacity of the fire side of the pylon gradually decreases,and the lateral displacement of the fire side of the bridge tower gradually develops to the fire direction,reaching the maximum of 0.21 m.The longer the fire combustion time or the greater the explosion equivalent,the more serious the local damage of the pylon caused by fire and explosion.Reasonable arrangement of diaphragms can effectively improve the blast resistance of pylons.Under the combined effects of fire and explosion,the overall bridge tower moves towards the direction of the explosion source in fire and explosion.With the extension of combustion time,the lateral displacement of the bridge tower under the explosion load gradually increases.