Research On Optimization Of Main Parameters And Section Form Of Wide Continuous Rigid Frame Bridge

With the rapid development of China’s economy and the continuous development of modern transportation system,the demand for long-span continuous rigid frame Bridges has been further improved.With the improvement of people’s living standard and the increasing number of families with cars,the two-lane road has been unable to meet the current driving requirements,so the need to build wide and long-span roads and Bridges has been shown.For the southwest region with special topography and landform,wide continuous rigid frame bridge has become a widely used and economical bridge structure due to the limitation of mountain terrain.This paper focuses on the study of a four-lane continuous rigid frame bridge with a span between100 and 200 meters.In the bridge design,the box beam section can be selected from single box single room and single box double room.Therefore,this paper studies the wide continuous rigid frame bridge based on the optimized analysis of the box girder beam height and beam bottom curve parameters,and comprehensively analyzes the best in consideration of the safety margin,the safety of the cantilever pouring basket construction and the amount of materials.The cross-sectional form provides a certain reference for future bridge design.The main research contents and achievements of this paper are as follows:(1)The structural design parameters of several continuous rigid frame bridges were investigated respectively,and the commonly used value ranges of parameters such as edge-to-span ratio,high-span ratio,power curve and box girder plate thickness were selected from the design of bridges built at home and abroad.Among the many types of bridge piers,comparing the thrust stiffness and bending stiffness of the bridge piers,it is concluded that the bridge piers with thin-walled piers have better forms.(2)In this paper,based on the Ganshui Bridge,Jianbaoliang Bridge and Wuchahe project,different power curves at the bottom of the beam are selected to establish a finite element model for calculation,and the variation of stress and displacement under constant load is analyzed.Considering multiple indicators such as structural strength,deflection and concrete dosage,and using a single comprehensive evaluation indicator instead of multiple indicators to evaluate different beam bottom curves,the power curve of the beam bottom with different spans is obtained.By changing the height of the root and mid-span,the change of the internal force of the control section of the bridge under constant load is analyzed,and the grid search method is used to find the optimal high-span ratio of different spans using structural optimization theory.(3)Based on the design and parameter optimization of the built bridges,continuous rigid frame bridges with three cross-sections of 120 m,150m and 180 m are designed.By establishing a finite element model,the safety margins of brid ges with different cross-section forms are compared from the flexural bearing safety margin,the normal section crack resistance,the diagonal section crack resis tance,the normal section compressive stress tolerance,and the local lateral anal ysis.By comprehensively comparing the amount of concrete in the superstructure of the full bridge and the amount of prestressed steel strands,the total cost of the two cross-section bridges under three spans is compared.The research results of this paper can provide a positive reference for the future construction of similar bridge types and further research.