Model Experimental Study Of Deflection Of The Cracked Prestressed Concrete Beam

The prestressed concrete bridge in long-term operation service period, may appear the phenomenon of cracking and deflection. The increase of crack in beam can reduce the stiffness, exacerbate span deflection, span deflection further aggravate beam cracking, both influence each other in a vicious circle, the phenomenon of prestressed concrete bridge has gradually become highly concerned issues. The research of deflection of beam ultimately is the research of stiffness, but the deflection calculation of cracked prestressed concrete bridge is essentially different with deflection calculation proposed by norm. Now conduct theory and model experiments of deflection calculation of cracked prestressed concrete bridge.In this paper, measured from the bending crack parameters of prestressed concrete beam, according to the difference of characteristics of cracks along the. vertical distribution, using the similar fracture treatment principle, the beam is divided into stepped-weir stiffness distribution girder beams, based on the crack characteristics calculating the effective stiffness of the crack part of the cracked prestressed concrete beam, proposing the deflection calculation method of cracked prestressed concrete beam based on the characteristics of the stiffness of stepped-weir.Through the prestressed concrete T beam model test, has studied the relation between loads and bending crack characteristics statistical parameters(crack average height, total width, the maximum crack width, crack area) and the deflection, according to the similar fracture treatment principle, the beam was divided into several sections girder crack, get the crack statistical characteristics of different sections, according to the model of beam stiffness direct calculation method and theory stiffness calculation method calculated the cracking of each section of the effective rigidity section. Used the deflection calculation method proposed by the paper, calculated the deflection under various load of the cracked prestressed concrete beam, and compared with experimental value. Test results show, the deflection based on《Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts》(JTG D62-2004) is bigger than experimental value. According to the statistical parameters of crack characteristic, used section linear elastic analysis method and the deflection calculation methods proposed in this paper calculated the deflection value of model beam under the load of classification, calculation results show that the calculation basic close test values. According to the statistical parameters of crack characteristic directly introduced model beam stiffness, and then calculated the deflection of cracked prestressed concrete beam, the deflection basic close to the experimental value, but slightly higher than deflection value calculated according to section linear elastic analysis methods.