Experimental Study On Behavior Of Prestressed Composite Girder Bridges Under Negative Moment And Its Applications In Engineering

Many differents exist between prestressed steel-concrete composite girders for negative moment and for positive moment. Concrete plate is easy to crack because of the tension force. Steel girder is easy to buckling under compresss. The behaviors of shear connector in negative moment are different between in avtive moment.18 push-out tests are engageded in order to study the behavior of stud under positive moment and 9 drag-out test are engageded to study the behavior of stud under negative moment. 9 experiments of steel-concrete composite box gieders were accomplished including 2 gieders under positive moment and 7 under negative moment. At last, the fruits of this paper had got application in a bridge. The main jobs and achievements are sumed up as follows:1) If strength of concrete is greater than 30MPa, the diameter of stud is a decisive factor to affect the shear capacity. The effect of strength and steel fibre contents of concrete is very minor. They can be ignored. Shear stiffness and slip between steel gieder and concrete plate display hyperbolic function relation. The diameter of stud and strength of concrete are main factors to affect the shear stiffness.2) The push-out test results of shear bearing capacity is about 1.5 - 2.2 times of the value of current design specifications. The drag-out test results is obviously lower than that of push-out test. The shear bearing capacitys under negative are about 0.41-0.68 times of it's under poative moment.3) Crack of concrete plate is related to the arrangement form of studs. The maximum width of cracks will be reduced adopting the arrangement form to use thin and dense studs, the maximal spacing should be restricted.4) The strain of the test girders were coincides very well with the compute result by the transform section method under elastic state. The shear force that steel web bears accounts for 35%-76% of total shear force.The above-mentioned experiment and theory achievement were applied in a 3 spans continuous steel-concrete bridge. All of behaviors of the bridge satisfy the specification request. These results indicate that the methods and conclusions of this...