Model Experimental Study On Precast Segmental Concrete Beam Bridge With External Prestressing And Dry Joints

Compared to monolithic girder with internal and bonded tendons, segmental precast concrete bridge, which combinded with internal and external tendon, has prominent advantages, many related engineering project had constructed in foreign countries, and it also gradually used in some approach span of the long span bridge and rail transit bridge in our countries. Existing research results at home and abroad show that the segmental precast girder, which combinded with internal and external tendon, has better flexural strength and ductility than segmental precast beam with whole external prestressing, internal tendon can restrain joint opening and the development of crack, thus enhancing the shear bearing capacity of segmental precast bridge. However, the precast concrete beam combinded with unbonded internal and external tendon with dry joints have not addressed by previous studies, in order to promote its application, based on summarizing and analyzing related research results domestic and overseas, funded by guangzhou science and technology plan projects(2008J1-C201)"Study on New Technology of Segmental Precast Construction with External Tendons", the shear and bending behavior of segmental precast concrete beam combinded with unbonded internal and external tendon with dry joints is analyzed through theory studying, model experimental testing and checking the simplified calculation method. The main research works are as follows:(1) Analyzing basic mechanical properties of segmental precast concrete beam with external tendon, summarizing related standards and simplified calculation method at home and abroad, and pointing out the advantages and disadvantages of all kinds of simplified calculation method.(2) Scale model experimental research on mechanical behavior of segmental precast concrete beam combinded with unbonded internal and external tendon with dry joints tests five specimens. The effects of construction method, ratio of unbonded internal and external tendons, and shear span ratio to the development of cracks and deflection and failure mode are studied. Mechanical behavior and failure mechanism of segmental precast concrete beam combinded with unbonded internal and external tendon with dry joints are systematically summed up, which is aimed to provid the basis of establishing and verifying the simplified calculation method.(3) In order to provide some preliminary rule of simplified calculating method of segmental precast concrete beam combinded with unbonded internal and external tendon with dry joints under the limit state, the representative standard formulas and simplified calculating method are computed and compared with the experimental data.