Structural Performance Analysis And Fire Resistance Design Of Steel Truss Arch Bridges Under Fire

In recent years,China’s transportation infrastructure construction has developed rapidly,and bridge engineering has also made extraordinary achievements.However,bridge fire accidents have occurred from time to time,causing significant losses to people’s lives and property.Compared with the field of housing construction,there are many deficiencies in the research of bridge fire resistance in China,especially for the fire research of long-span steel bridges.With the development of bridge construction and the increase in the total amount of bridge transportation,the safety analysis of bridge structures under automobile fires will become increasingly important.The Sulingshan Bridge in Xiangyang is a large-span down-through steel truss arch bridge with a span of 70 m + 240 m + 70 m.It is an important traffic link connecting Xiangzhou District and Dongjin New District.Taking this bridge as the research object,the structural performance analysis and fire resistance design research of large-span steel truss arch bridge under automobile fire were completed based on the concept of structural performance-based fire resistance design.The main research work and conclusions of this article are as follows:(1)The typical research results of steel properties at high temperature are summarized,and appropriate thermal and thermodynamic parameters of steel are determined.Summarize various typical models of heat release rate of automobile fire,Determine the model of heat release rate of automobile fire used for fire research of Sulingshan Bridge.(2)The load transfer characteristics of long-span steel truss arch bridges were analyzed.The bridge structure analysis finite element program Midas / civil was used to calculate the stress conditions of various components of the Sulingshan Bridge during normal operation,and combined with the impact of fire on structural performance The law determined the most unfavorable fire scene of Sulingshan Bridge when it suffered a car fire.Studies have shown that the Sulingshan Bridge is the most unfavorable fire scenario when a tank truck fire occurs at the lower chord arch foot position and the mid-span position of the main span.(3)Use the fire dynamics simulation software FDS to establish a thermal analysis model of a tank truck fire at the foot of the lower chord arch and the mid-span of the main span of the Sulingshan Bridge.Distribution of transient temperature field.The research shows that the spatial difference of the bridge fire temperature field is obvious,and the temperature of the members in different space locations is very different,while the temperature difference of the steel member along the thickness direction of the section under fire is relatively small,and the steel truss arch rib member under the action of a tank truck fire The maximum temperature can reach 893.7 ℃.(4)The finite element software ABAQUS is used to establish a full-bridge thermal-structure coupling analysis model.The three-dimensional transient temperature field of a component under a car fire is applied as a thermal load to the thermal-structure coupling model,and the large-span steel truss arch bridge is obtained.Changes in structural performance under the two most unfavourable fire scenarios.Studies have shown that under the action of a tank truck fire,the steel truss arch rib members are at risk of yield failure,the load capacity of the sling is almost completely lost,and the maximum vertical displacement change of the full bridge under the action of fire can reach-419.4mm.(5)The fire protection design of the steel truss arch ribs and slings of the Sulingshan Bridge was carried out to determine the fire protection height of the steel truss arch ribs and slings and the thickness of the fire-resistant coating.Studies have shown that setting fire protection measures can effectively delay and reduce the impact of fire on the structural performance of steel truss arch bridges.