Fire temperature load model and influence analysis of bridge tower structure
In order to study the influence of fire on the bridge tower,the fire temperature load model of the near-fire surface of the bridge tower was proposed,and the fire effect of the whole tower structure was analyzed.The steel-concrete composite bridge tower with a height of 345 m was used as the research object,seven fire scenarios were set up,then,the temperature distribution of different fire scenarios was obtained by fire dynamics simulator(FDS).Based on the distance and height parameters,the temperature load model formula of near-fire surface fire was established.The temperature load model was used as input,and the transient temperature field within the wall of the bridge tower was calculated.Furthermore,the mechanical properties of the bridge tower under fire were analyzed by sequential coupling force field.The results show that when the distance between the fire source and the tower surface is close,the flame will stick to the wall,the temperature near the fire surface is higher and the temperature gradually decreases along the height of the tower.When the distance between the fire source and the tower surface is far,the overall temperature of the near-fire surface is low.The inclination of the bridge tower makes the highest temperature of the near-fire surface appear at the height of the flame closest to the bridge tower.In the thickness direction of the bridge tower,the temperature decreases rapidly along the thickness direction and the starting point of temperature rise gradually lags behind.The maximum stress value of the bridge tower under different fire scenarios depends on the temperature of the near-fire surface,and the stress is concentrated in the area where the temperature of the near-fire surface is high.With the development of fire,the stress concentration area gradually develops from high temperature area to low temperature area.When the temperature near the fire surface is low,the thermal expansion effect will cause the lateral displacement of the bridge tower away from the fire source direction,while the high temperature will lead to a significant decrease in the bearing capacity of the near-fire surface and its internal materials,and the lateral displacement develops near the fire source direction.The lateral displacement caused by fire during tower construction is smaller than that during operation.1 tab,13 figs,30 refs.
bridge engineeringbridge towertemperature load modelfire dynamicsfire effecttemperature field