Model Flexural Tests For 30m Pre-Tensioning BULB-T Beams With Bent-up Tendons

With the development of society and economy,the requirement of construction technology based on quality,speed and durability has become increasing important in civil and traffic construction.The structure based on standardization,assemblage has become the prior option in bridge construction.BULB-T beam bridge consist of BULB-T beams,diagram,concrete slab and connection system.Each component can be prefabricated,which can effectively improve the durability of the structure and on-site construction speed.The BULB-T beam is prestressed concrete element with bent-up tendons,which overcome the shortage of traditional straight-line prestressed concrete components that cannot be applied to large spans,at the same time,avoid the durability problems which caused by grouting in post-tensioned concrete structure.BULB-T beam has been widely used in the construction of small span bridges abroad.This paper include the model test of flexural and prefabrication method for 30m pre-tensioning bulb t beams with bent-up tendons,summarize the structural characteristics of BULB-T beam bridge,provide basis for the generalization and application of BULB-T beams.The main contents and conclusions are given as follows:1.A systematic introduction and analysis on basic structure features of BULB-T beam bridge.Including longitudinal and vertical layout of bridges,design points of section form and einforcement and prefabrication methods,bridge decks and diagram form,connection forms of various components,etc.The structural forms and prefabrication methods applicable to different conditions were compared and analyzed.2.The Pre-stress friction loss of BULB-T beam has been measured during prefabrication,the main stress in end scetion of BULB-T beam and deformation has been measured after releasing tendons.Verification of pre-stress friction loss calculation method for bent-bending steel bending beam,reasonable prestressing sequence is proposed.3.A full scale model of 30m prestressed concrete BULB-T beam with bent-up tendons was subjcted to a static loading test.The evaluation of flexural performance of BULB-T beams from failure modes,failure mechanism,flexural ultimate bearing capacity,rigidity and crack resistance of test beams has been compared,which indicate that BULB-T beam has great capacity of ultimate flexural capacity and displacement ductility.4.According to the standard of concrete bridge of China and US,the bending indicators of BULB-T beam has beem canculated.The calculated results agree well with the test results,which indicates the Chinese specification can be applied to the flexural performance design of the BUBL-T beams.