The Research To The Crack Disease Of Prestressed Concrete Slab-beam

The pre-stressed concrete continuous slab-girder bridges have simple structure and definite mechanics. They have been extensively used on highway bridge. Along with the highly development of the modern technology on bridge construction and innovation of bridge design theory, this form of bridge has a tendency on longer continuous beam and lighter structure. The tendency obtained much good economic efficiency but also brought with several problems. For example, minify too much on the section of hollow slab results inadequacy bearing capacity, longitudinal cracks by distortion effect, the continuous length is too long together with the failure of bearing device also results inadequacy bearing capacity. Besides. The paper summarized the typical failures of this form of bridge, verified the dominant reasons of the failures, and presented some theoretic reference on this form of bridge.(1) Employed the thin-walled structural theory to investigate the regular longitudinal cracks of the thin-walled hollow slab span. The energy method and finite strip method were conducted to calculate the distortion stress of the hollow slab under live load, and the distortion analysis on the current standard hollow slab was also presented. The theoretical analysis and the field load test verified that the distortion effect is the dominant reason causing the longitudinal cracks of the hollow slab.(2) Analyzed the dominant factors of transverse effect of distortion, including the width and thickness of boards, transverse diaphragm and lateral join of slabs. Also, present optimization design on section of thin-walled hollow slab.(3) Focus on the longest continuous beam, established 2-D FE model which considered interaction of substructure and superstructure to check the stress level and bearing capacity. Further, discussed the rational relation between the stiffness of substructure and continuous length, and presented the largest continuous length on vary substructure base on no-sliding bearing, and investigated rational largest continuous length for whose piers placing two-row bearing.(4) The paper also analyzed the longitudinal cracks of bridge deck pavement along the linkage, by establishing 2-D FE model and 3-D FE model of the illustration which has a 3-bearings support mode together with thin linkage. The calculation results verified the over-thin linkage is the dominant reason causing lateral stress out of limitation, and results the longitudinal cracks of deck pavement.