The Cracked Model Test Study Of Pre-stressed Concrete Box Girder

PC box girder is very suitable for large-span structures such as continuous box girder and continuous rigid frame because of their huge flexural stiffness, torsional stiffness, and ability to bear the sagging and negative moment. At present, this kind of bridge type structure is used extensively. However, cracking phenomenon of prestressed concrete continuous box beam and prestressed concrete continuous rigid frame bridge is common in the operation process, influence the security, durability and service life of the bridge directly; the safety evaluation towards PC box girder after cracking should be proposed urgently. Therefore, a study on damage assessment of crack of prestressed concrete box beam has applicable value in engineering.As an important part of communication science and technology item of the Western-'A study on the causes and diagnosis technology of existing PC box girder and rigid frame bridges'(2003-2105), this paper puts experimental study into focus, combined finite element analysis software ANSYS and prestressed concrete box-section analysis methods, the bearing capacity gradation state of prestressed concrete box beam with flexual and shear cracks is studied. Two simply supported beam and cantilever beam model were designed and manufactured which had the same material, law of cracks and bearing capacity gradation state of prestressed concrete box beam at serviceability limit states were analyzed through multi-stage loading test. Based on the measured parameters cracks, finite element damage model was established, and compare the result of numerical calculation with model test, some extremely valuable conclusions were obtained.According to the experimental data, under the designing load control stress state, the bending stiffness reduction coefficient of two simply supported beams with vertical bending crack is 0.6 and 0.65 respectively; along with increasing of cracks in amount or width or height, the bearing capacity deduction coefficient of two simply supported beams is 77.8% and 71.8% respectively. Under the designing load control stress state after shearing crack of prestressed concrete box cantilever beam, the bearing capacity deduction coefficient of two simply supported beams is 81.5%and 79.1%respectively. Regularity of service performance between testing value and theory value is unanimous. A reference is offered by this paper for evaluating similar bridge structure safety.