Research On The Overturning Stability Of The Single-Pillar Ramp Bridge Under The Conditions Of Accident Vehicle Rescue

The one-pillar ramp bridge is a special bridge form of the highway ramp bridge,which is easy to deflect under the action of vehicles,leading to displacement or even overturning of the bridge structure.At the same time,large and heavy vehicles on the highway are increasing day by day.Accidents of vehicle rollovers on the highway ramp bridge also occur frequently.Considering that the rescue after the special heavy vehicle accident may cause harm to the safety of the ramp bridge.Therefore,this paper relies on the typical single-pillar ramp bridge of Ningbo Expressway,studies the working conditions of heavy cranes to rescue heavy vehicles after the heavy vehicles roll over,and analyzes the stress conditions and the most adverse effects of the ramp bridge.Based on the research of these situations,a solution to the accident of a rollover of a heavy vehicle on a singlepillar ramp bridge on a highway was proposed,thereby providing technical support for the longterm safe service of the single-pillar ramp bridge.First,based on the analysis of the most unfavorable working conditions of different heavy accident vehicles and cranes on the bridge and lifting and rescue,the overturning of the ramp bridge is checked,and the anti-overturning coefficients of the ramp bridges with different single pillars are obtained.Reasonable driving range on the ramp bridge.Secondly,for the lifting of the crane,the internal force of the bridge was checked,and the most unfavorable load combination was carried out,so as to check whether the crane lifting meets the bridge’s stress requirements.At the same time,the paper carried out the local internal force check calculation of the ramp bridge deck under the crane load,checked the bearing capacity requirements of the box girder wing plate under the bearing capacity limit state,and put forward the corresponding requirements for the reasonable placement of the crane.Finally,the article carried out the overturning stability check on the working conditions of the cranes rescued by the straight and curved bridges under three overloaded truck loads,and obtained the limit loads that the cranes could be rescued by the straight and curved bridges.The research results show that:(1)Curved bridges have a greater risk of bearing vacancy during the rescue of cranes than straight-line bridges,and the risk of bearing evacuation when the cranes on the bridge rescue the accident vehicles is greater than when the cranes lift the rescue vehicles.In order to reduce the risk of emptying the support,it is recommended that the rescue crane travel on the area near the center line when rescue the accident vehicle on the straight ramp bridge;The rescue crane travels on the centripetal side of the ramp bridge.(2)Under normal circumstances,the anti-overturning stability coefficient of the ramp bridge when the crane rescues heavy vehicles can meet the requirements of the specification.When a large-tonnage crane rescues a large-tonnage vehicle,the overturning coefficient is smaller,which means that the heavier the accident vehicle,the greater the risk of overturning of the ramp bridge during the rescue of the crane.(3)Although the bending moment internal force on the main beam is still within the safety range of the bridge design during crane lifting operation,for safety reasons,it is recommended that the crane be placed as far as possible to avoid the mid-span of the main beam Unfavorable positions such as medium and side span 0.4L.(4)When the crane lifts the accident vehicle,the bridge deck of the ramp bridge has the risk of insufficient local bearing capacity.Measures such as adjusting the position of the outrigger of the crane,increasing the size of the outrigger pad,and speeding up the rescue process can be taken to reduce the damage to the bridge deck.(5)Under the most unfavorable rescue working conditions,with the increase of the radius of curvature and the increase of the joint bearing spacing,the lateral anti-overturning stability of the curve bridge has a tendency to increase.In the meantime,the radius of curvature of the curved bridge and the spacing of the joint supports should be appropriately increased to help improve the anti-overturning stability of the curved ramp bridge with single column pier.(6)For the calculation of three overloaded vehicle loads of 45 tons,55 tons and 65 tons under the rescue condition of 200 tons crane,it can be known that the support of the linear bridge begins to be emptied under the rescue effect of the crane of 65 tons.Under the rescue effect of the 55-ton vehicle load crane,the curve bridge began to appear to be vacant.It is estimated based on the interpolation method of the minimum support force under the rescue action of the 45-ton,55-ton and 65-ton vehicle load cranes.The maximum vehicle load that can be rescued by a straight bridge is 56 tons,and the maximum vehicle load that can be rescued by a curved bridge is 48 tons.