Research On Vehicle-load Effect And Vehicle Weight Limit Of Existing Bridges

Among the existing bridges there are quite a few in the poor technical conditions,which is in the state of "sick work".However,the growth of traffic volume and freight volume in recent years bring to "scarred" bridge greater security risks.So make a reasonable vehicle-load limit standard for existing bridges is imperative.The key to develop the load limit is to evaluate the existing state of the bridge,that is,to evaluate the existing carrying capacity and the vehicle-load effect.The other members of the research group have achieved some achievements in the evaluation of the carrying capacity of the existing bridge.This paper mainly aims at the study of the vehicle-load effect of the bridge.Considering the randomness of the influencing factors and the fuzziness of the hierarchical division,a stochastic fuzzy comprehensive evaluation system for vehicle-load effect is established.On this basis,the general flow of the load limit analysis is established.The main achievements are as follows:1)The main influencing factors of vehicle-load effect separated from the specification and related literature are traffic volume,vehicle load and vehicle axle load.The probability distribution characteristics of influencing factors are discussed,and the stochastic properties of the evaluation index(Qm/Qd,?,?)are deduced not to reject the normal distribution.2)In order to make reasonable value,the concept of fuzzy mathematics is bring to the value of live load influence correction coefficient.Build evaluation sets based on characteristics of evaluation index(Qm/Qd,?,?),and build membership function according to the general principle,then,the fuzzy comprehensive evaluation model of each correction coefficient(?q1,?q2,?q3)is established.On this basis,combined with Monte-Carlo stochastic simulation,a random fuzzy comprehensive evaluation system of vehicle load effect is formed.3)The evaluation system of limited vehicle-load for existing bridges is established,in which taking the heavy truck of vehicle fleet as the limit load model,and the reliability index of the structure as the limit load standard.When the bridge required load limit,the stochastic fuzzy evaluation system is used to calculate the reliability index of the structure under different levels of vehicle load,and select reasonable limit standard in comparison with the minimum allowable reliable index.The results show that the stochastic and fuzzy comprehensive evaluation system can take the change of traffic volume and the change of vehicle load into account,which can meet the needs of the current traffic condition and meet the needs of the reliability assessment.It is safe and reliable than the standard evaluation method.The load limited evaluation system is practical and can provide the basis for the safe operation of the bridge.