The Mechanism And Countermeasure Of Cracks In Webs During Continuous Beam And Continuous Rigid Frame Bridge Constructing

Continuous beam and continuous rigid-framed bridge with reasonable force,good structure and beautiful shape,is most widely used in bridge engineering.It is the main beam that use box-section.Continuous beam and continuous rigid-framed bridge with box section, cracks in a quarter span of webs was found in some bridges during the construction.Cracks have seriously affected the usefulness and durability of the bridge.Therefore,analysis of the cause has great significance.In this paper, a practical bridge in Qinghai which adopts single box and single room structure was discussed. There is a web crack on the place a quarter to one end. This paper use ANSYS to establish a 3-dimentional model to analyse the reason which cause the crack in the webs. Linear Elastic Mechanics was used firstly to calculate the maximum principal tensile stress in webs, and then using nonlinear finite element solid65 in ANSYS to simulate reinforced concrete, to analyse the crack in webs.Based on the above analysis, the following conclusions can be gotten:1), It will not occur webs crack, when the bridge on the basis of drawings of engineering designs and product designs, at first longitudinal prestressed reinforced, the principal tensile stress within the webs overtake designcriterion.2), In order to prevent internal tension stress in webs from exceeding the tensile strength of concrete, one should stretch the vertical prestress firstly and then stretch the vertical prestress.3), It should increase the density of the piping points to prevent the moving of the pipes when the prestressed tendon are piping.