| In order to meet the traffic needs of more lanes and vehicle types,the width of the bridge deck is gradually increasing,and large-span bridges with wide and asymmetric bridge decks are increasingly being applied in practical engineering.Long span bridges located in strong wind areas have a more complex driving wind environment due to the high wind speed in the driving space of the bridge deck,as well as the influence of the auxiliary structures and bridge towers on the bridge deck.In recent years,high-speed vehicles have experienced multiple safety accidents such as side slip and rollover under the strong crosswind.Therefore,reasonable control measures need to be taken to ensure the safety of bridge deck driving.This thesis is based on the engineering background of a double tower cable-stayed bridge with a 454 m main span on the same floor of a public rail asymmetric wide bridge deck spanning the Yangtze River.In order to obtain the wind environmental characteristics of the asymmetric bridge deck on the same floor of the public rail and achieve the safety of driving in the tower area,the main research content includes the following aspects:(1)Based on the non bridge tower area main beam section in the engineering background of this article,the process and method of CFD numerical simulation are elaborated,and a three-dimensional simulation model is established.FLUENT fluid simulation software is used for flow field numerical simulation to analyze the characteristics of the wind environment at different windward sides and different wind attack angles within the bridge deck driving height.The results indicate that there are significant differences in the wind field characteristics of the bridge deck when facing the wind on different sides of the public rail,and different wind attack angles have a significant impact on the equivalent wind speed of the bridge deck.(2)Based on the three-dimensional simulation model of the main beam and bridge tower at the 50 m section of the bridge tower,the wind field distribution of the bridge deck driving height in the bridge tower area is simulated with a 0 ° wind attack angle under crosswind,and the equivalent wind speed distribution of the bridge deck at different positions from the windward lane to the center of the bridge tower is obtained.This provides a data basis for the subsequent safety analysis of vehicle roll and slip on the track side and road side.The results indicate that the wind field undergoes severe amplification on both sides of the bridge tower,and the equivalent wind speeds on the bridge deck of the windward lanes on both sides of the public rail in the tower area are significantly greater than those on the bridge deck of the windward lanes in the non tower area.(3)Select vehicle models and related parameters on the track side and road side,conduct force analysis on different vehicle types’ roll and slip safety states,obtain the equivalent wind speed of the bridge deck for the critical state of vehicle roll and slip,and then analyze the driving safety of vehicles on the windward lane.The results indicate that a train may pose a safety threat to roll at a speed of 120km/h;The crosswind stability of basic passenger vehicles on the road side is better than that of large commercial vans,but side slip safety accidents may still occur under adverse road conditions.(4)Based on traffic safety analysis,wind barriers are installed on both sides of the public rail bridge deck.The equivalent permeability method is used to study the changes in the wind environment under different permeability wind barriers,improve the safety of driving in windward lanes,and provide reference for similar engineering research.The results indicate that a 75% ventilation rate wind barrier outside the rail side railing in the tower area can prevent train roll accidents,and the safety of driving with different ventilation rates on the collision barrier on the road side has been improved. |
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