Prestress Optimization Design And Blind Zonestudy Of Main Girder Of PC Continuous Rigidframe Bridge

In this paper,the monitoring project,the dam bridge,is used as the engineering background.The finite element software Midas/Civil and the entity software Midas/FEA are used to optimize the design of the prestressed system of the continuous rigid frame bridge.The idea of re-bending the longitudinal prestressed beam and eliminating the downward bending of the web is proposed.The design of the vertical prestressed beam layout is strengthened,and the longitudinal roof bundle,the bottom bundle and the vertical bundle are formed.The core prestressing system.The following research work has been done on the optimal design of the prestressed system:(1)The characteristics and research status of continuous rigid frame bridge are summarized.The development trend of continuous rigid frame bridge is analyzed,and related problems are proposed for prestress design.The related situation of the prestressed optimization design of the continuous rigid frame bridge is studied.The idea of eliminating the prestressed beam of the web under the bend is proposed,and the research significance of eliminating the downward beam of the web is analyzed.(2)The pre-stress design method based on reasonable bridging state is used to re-distribute the longitudinal prestressed beam of the down-bend bundle.The characteristics and influencing factors of the reasonable bridge state are studied,and the overall design idea of the longitudinal prestressed beam under reasonable bridge condition is proposed.(3)Using the finite element software Midas/Civil to simulate the distribution of the internal force of the main beam.The prestressing values of the main beam sections under reasonable bridge conditions are calculated by the load balancing method.Then,the longitudinal prestressing beam distribution formula of the box girder based on the minimum bending energy principle is derived by the balance principle of bending strain energy.The beam and bottom plate bundles of the box girder are re-matched by the derived beam-sharing formula,and the results of the re-bundling are checked and verified under the condition of the bending moment feasible domain.(4)The theoretical analysis of the feasibility of canceling the downward bending of the web was carried out,and the design of the vertical prestressed beam was strengthened.The stress analysis of the main girder web under the normal vertical arrangement and the inclined arrangement is compared and analyzed.Finally,the reasonable range of the vertical prestressing tendon inclination angle after the bendingof the web is obtained.Based on the orthogonal design principle,16 sets of orthogonal tests were carried out on the values of the vertical prestressed tendons,and the reasonable spacing was obtained.(5)In order to eliminate the reasonable value range of the vertical prestressing tendon angle after the downward bending of the web,nine different vertical prestressing tendon arrangements were established.Using Midas/FEA to model and compare different layout schemes,analyze the vertical stress and maximum shear stress of the inner and outer sides of the web under different vertical prestressing schemes,and obtain a reasonable vertical pre-section of each section of the main beam.Stress layout scheme(6)The origin of the blind zone under the action of vertical prestressed tendons is introduced.The solid finite element software Midas/FEA is used to simulate the vertical prestressing tendons of the 1# to 6# box girder sections in vertical arrangement,inclined by 10° and inclined by 20°.The diffusion effect of prestress under three arrangements.By extracting the vertical prestressing stress value on the section of the vertical prestressing tendon where the web is located,and analyzing the stress values under the eight stress transfer paths,the prestressed blind zone under each beaming mode is obtained.