波形钢腹板-钢底板组合箱梁耐火极限与设计

Fire Resistance and Design of Composite Box Girder with Corrugated Steel Webs and Steel Bottom Plate

研究目的:近年来交通量的增加,由车辆碰撞或易燃物品运输车辆引起的桥梁火灾时有发生,不容忽视。为了解火灾下波形钢腹板-钢底板组合箱梁的火灾响应,采用ANSYS建立三维热-力耦合分析模型,分析火灾下组合箱梁温度场分布状态与抗弯承载力衰变规律,研究不同受火场景对组合箱梁耐火极限的影响,提出抗火设计方法。研究结论:(1)火灾下组合箱梁截面抗弯承载力呈三阶段发展;不同受火范围下跨中挠度随受火时间延长均呈两阶段发展;随着受火长度的增加,组合箱梁挠度增长幅度越大,受火初期受热弯曲效应作用越显著;(2)与抗力准则相比,采用挠度破坏准则判定组合箱梁的耐火极限较安全;(3)在组合箱梁底板增设不同类型的加劲肋形式,均可提高组合箱梁的耐火极限,当加劲肋材料用量相同时,与增设通长加劲肋相比,增设底板局部加劲肋对组合箱梁的耐火极限改善效果更好;(4)本研究成果可为波形钢腹板-钢底板组合箱梁的耐火极限理论分析与抗火设计提供参考。

Research purposes:In recent years,the increase in traffic volume has raised concerns about bridge fires resulting from vehicle collisions or the transportation of flammable materials.To understand the fire response of composite box girder with corrugated steel webs and steel bottom plate,a three-dimensional thermal-mechanical coupling analysis model was developed using ANSYS.This model analyzed the temperature field distribution and the decay of flexural bearing capacity under fire conditions.Additionally,it examined the impact of various fire scenarios on the fire resistance limit of the composite box girder and proposed fire-resistant design methods.Research conclusions:(1)The flexural bearing capacity of composite box girders under fire conditions progresses through three stages.The mid-span deflection,across various fire lengths,develops in two stages over time.As the fire length increases,the deflection growth rate of the composite box girder becomes more significant,with a more pronounced thermal bending effect during the initial fire stage.(2)Using the deflection failure criterion to determine the fire resistance limit of composite box girders is safer than using the resistance criterion.(3)Adding various types of stiffeners to the bottom plate of composite box girders improves their fire resistance limit.With the same amount of stiffener material,local stiffeners on the bottom plate enhance the fire resistance limit more effectively than continuous stiffeners.(4)The research findings can provide a reference for the theoretical analysis and fire-resistant design of composite box girder with corrugated steel webs and steel bottom plate.