Construction Technologies And Construction Scheme Selection Method For Bridge Across Railway Lines

Thanks to the rapid development in the infrastructure construction such as railway,highway,municipal works,and light rail transit projects,the intersection between those newly built projects and the existing railway lines increased sharply.In most cases of such intersection,grade separation applies,for instance,the newly built project either run underneath or run over the existing railway line.In case of the former mode,framed bridge constructed with jacking method or tunnel is generally adopted to run underneath the existing line;In case of the later mode,bridge is often erected to run over the existing line.This thesis addresses the construction technologies of overpass bridges,makes analysis to the major factors influencing the construction of overpass bridges and makes proper induction and study on the comparison and selection of overpass bridges construction scheme under situations of complexity.Start by generalizing the regular forms of bridge,such as the prefabricated bridge and cast-in-place bridge,and the construction clearance and construction protection methods as stated by the Regulations of Railway Technical Management(RRTM),the thesis then focuses on some regular construction technologies of bridge running over existing lines,which includes erection of prefabricated bridge by crane and bridge erector,construction of cast-in-place bridge by bracket method or case-in-place cantilever method,construction of bridge by rotation and incremental launching method.Introduction and comparative analysis to the key construction technologies as involved in relevant methods are made in terms of budget cost,construction safety,construction period,project quality and influences to the existing railway lines.Based on the concrete project practice,the thesis make brief introduction of the construction scheme,construction arrangement during time window,selection and configuration of machinery and equipment,construction technique and process,together with a brief introduction of the construction technologies such as portal piers and bridge assembly by bracelet method.Factors influencing the overpass bridge construction scheme are also analyzed in terms of their budget cost,construction safety,construction period,project quality and influences to the existing railway lines and study are made to four common methods on comparison and selection of overpass bridge construction scheme,namely experience determination method,expert meeting method,expert scoring method,and analytic hierarchy process,and great importance are attached to the process and procedure gone through by the analytic hierarchy process.By analyzing the concrete project practice of overpass bridge under complex circumstances,this thesis presents in details the process of construction scheme comparison and selection by analytic hierarchy process method,primarily focus on project overview,proposed construction scheme,analysis of influencing factors on construction scheme,calculation of influencing factors over proposed construction schemes,and illustrates the process of modeling,calculating,test in order to arrive at construction scheme as well as the practice and effect of these construction schemes.In conclusion,this thesis proposes several conclusions and remarks on construction schemes of bridge over existing railway lines and the comparative selection of such construction schemes.