Experimental Study Of The Flexural Behavior Of A Precast Prestressed UHPC Thin-walled Bent Cap

Because of the large selfweight,conventional prefabricated concrete ben cap was inconvenient to transport and assemble.In addition,the cast-in-place concrete bent cap required large workspcaces and timescales.In order to realize the requirements of light weight,rapid construction,high strength and good durability,this paper proposed a novel fully prefabricated large-cantilevered thin-walled UHPC bent cap,which is convenient to transport and assemble.The on-site construction process was greatly reduced.According to the rapid reconstruction project of Xiangfu road in Changsha,a large-scale model test was carried out to study flexural and cracking behaviors.Theory analysis were conducted according to experimental results.The main research carried out in the thesis and its conclusions are as follows:(1)According to the supporting project,a novel fully prefabricated largecantilevered thin-walled UHPC bent cap was proposed.The flexural capacity,shear capacity and crack resistance of the bent cap was calculated and checked according to French and Swiss UHPC codes.The self-weight can be reduced by more than 40%,and the bent cap can lift in place at one time.Few prestressing tendons will be installed in the tension zone,and these tendons can be tensioned at one time to simplify the construction process.The requirements of fully prefabrication and assembly can be achieved.(2)A large-scale specimen with a similarity ratio of 1:2 was test to study flexural and cracking behaviors,and experimental results of the whole loading process were obtained.Experimental results indicated that the bent cap exhibits excellent structural and deformation behavior,the bent cap was failure when the applied load was approximately 1.8 times of the fundamental combination of actions.The bent cap possess good cracking behavior,the crack width of 0.05 mm was occurred when the applied load was approximately 1.2 times of the frequent combination of actions.Cracks are distributed intensively and evenly,showing multiple cracking characteristics.(3)Considering the tensile behavior of UHPC,the calculation methods for first cracking moment,nominal cracking moment and flexural capacity were investigated,and the calculation results were in good agreement with the test data.It is conservatively and safely recommended that the plastic influence coefficient should be1.0 and 2.0 to calculate the first cracking moment and the nominal cracking moment,respectively.It is suggested that the conversion coefficient k of the uniform stress distribution in the tension zone is 0.6 when calculating the flexural capacity.(4)Four kinds of lightweight UHPC bent cap were proposed,and the comparison of four designs were conducted in mechanical behavior,economics and constructability.These designs can provide reference for the application and development of fully prefabricated UHPC bent caps,improve the construction technology of prefabricated bridge in China,and further promote the development of accelerated bridge construction in China.