Research On Design And Construction Details Of UHPC Segmental Precast Bridge

Ultra-high performance concrete(UHPC)segmental precast girder bridges have many advantages,such as light weight,convenient construction,good durability and environmental protection.They are more and more widely applied in projects.At present,there are still few studies on the design of UHPC segmental precast girder bridges and something due to the enhancement of materials need further research.The overall design and local structural optimization of the UHPC prefabricated assembled girder bridges were studied on the basis of the work prepared by the local standard of Sichuan Province,“Technical Standards for Prefabricated Ultra High Performance Concrete(UHPC)segmental precast girder bridges in Urban Sections of Sichuan Province”.The research content includes reasonable values of various parameters in the overall design,design optimization of zero block and prestressed anchoring,and force performance of joints,which can provide reference for the design of UHPC segmental precast girder bridges.The 150 MPa grade UHPC material was used to design the 3×50m UHPC segmental precast girder bridges.The overall finite element calculation model was established by Midas,which was used to discuss the selection of sections,the division of segments,the arrangement of prestress,the ratio of high span,and the thickness of the plate.The research shows that a high span ratio of 1/30 can be used to design UHPC beam bridges.Compared with the ordinary concrete girder bridge,the UHPC girder bridge has a 1/2 reduction in plate thickness and a 40% reduction in self-weight.Due to the excellent material properties of UHPC,the thickness of the UHPC girder bridge is thin,which makes girders have poor overall stiffness,large torsional distortion,and difficulties in prestressed anchoring.The design of the UHPC girder bridge is also controlled by the local structural design.The ABAQUS finite element solid model was built to optimize the local construction of the UHPC girder bridge.For the zero block,the UHPC+RC combination was used to increase the stiffness and integrity of the zero block.For ordinary precast segments,a ring rib stiffening structure was designed,which can effectively improve the performance of UHPC thin-walled box girder against torsional distortion.When the external prestressing is anchored,tensile stress concentration will occur under the anchor pad,inside the anchor plate and inside the top plate of the anchor block.This phenomenon can be improved by strengthening the local plate thickness and increasing the length of the anchor block.The joint is the weak position of the UHPC segmental precast girder bridges,and its stress performance has a great influence on the overall force performance.A finite element solid model was established to compare different types of seam construction patterns and optimize the construction parameters such as the number of keys,depth,and inclination of the joint.After that,the constitutive model of Concrete Damaged Plasticity(CDP)was established to research the failure mode of the joint.And the influence of the relative size of the key teeth,the configuration of the key teeth and the lateral force on the force of the key joint was researched.The research shows that the joint is subjected to tensile failure.The lateral force has a great influence on the bearing performance of the joint,and the influence of the lateral force should be properly considered when checking the joint.