Study On The Risk Assessment And Protective Measures Of Bridge Superstructure Integrated Lifting

With the development of the city,the urban traffic system has been improved,which is convenient to travel.The process of the development of traffic system,the inevitable cross of new lines and existing lines produce a large number of crossing engineering.Crossing construction has certain requirements for space.When the existing bridge space is not enough,it need to adjust the height of existing bridge,then whole lifting of the bridge superstructure will solve this problem.However,as a kind of special project,the whole lifting of the bridge superstructure is complex,special and unexpected.It is a very important task how to avoid the occurrence of safety accidents.In this paper,the overall adjustment of Qingrong intercity railway overpass continuous box girder top up as the research object,it is systematically analyzed the risk factors influencing the construction safety,and established the risk evaluation model based on the improved AHP and fuzzy comprehensive evaluation method;According to the evaluation result,it sets up reasonable monitoring plan and protective measures to reduce the risk.It has a good effect and has provided valuable experience for similar engineering construction.In this paper,based on the actual situation of the project construction site and lifting scheme as the foundation,it is identified the main factors from the personnel,equipment,environment etc.,including temperature,wind load,the existing railway operation effect,improper selection of lifting point,bracket system instability,the upper structure deviation,monitoring scheme reasonable,updata of data feedback,lack of emergency plan,make no decisions from the feedback data,the uncoordinated units of communication,PLC hydraulic jacking system fault,follow-up supporting fault and no vertical position in lifting of the jack.On the basis of the above mentioned,the whole lifting index system of the bridge superstructure is constructed.Application of the improved analytic hierarchy process(FAHP)to calculate the weight of each index system,the risk matrix is obtained using fuzzy comprehensive evaluation method,through the weight value calculation and risk matrix,it is calculated level III of the whole bridge superstructure lifting risk.It is a serious risk,must pay attention to strengthen management and take measures to reduce risk.In order to reduce the bridge overall jacking-up risk,a reasonable monitoring program is formulated,according to two aspects of the geometric deformation monitoring and stress monitoring,at the same time it should be taken the four kinds of protective measures-the carrier system,vertical and horizontal spacing device,temporary block,coordination to ensure the risk control in the reasonable scope.