Experimental Study On Fatigue Behavior Of Prestressed Concrete Beams With Manufactured Sand

The sand is the common material in construction which has been used in great amount,not only directly applied in buildings such as roadbeds,bridges and culverts,tunnels and buildings but used in masonry of structure.With the fast development of capital construction,the natural sand resource has been reduced gradually and its surplus amount can not satisfy the demand in capital construction.As a result,the natural sand is replaced by manufactured sand produced from rocks and slag.This kind of production mechanism has been paid more and more attention.At present,prestressed concrete structure has been applied wildly in bridge construction.The manufactured sand of concrete in our country has not been widely used in prestressed concrete elements of the road and railway bridge engineering.In order to popularize and apply manufactured sand,this paper demonstrates the experimental study on fatigue behavior of three prestressed concrete beams with manufactured sand(two pre-tensioned beams with pretensioned bent up tendons,one parabola of post-tensioned).Its purpose is to provide reliable reference for the application of manufactured sand in the prestressed concrete structure.The research work of this thesis is shown as following:(1)The test results of the prestressed concrete beams with manufactured sand under loading are given.The prestressed loss of sand in the construction stage are analyzed.(2)On the basis of test,this paper analyzes the plane cross-section assumption is proved and the depth of compression zone changed little for the beams under fatigue loading.(3)Based on experimental results,the strains of concrete,stresses in prestressing tendons,stresses in reinforcement,the cracks development and the deformation rule of the prestressed concrete beams with manufactured sand under fatigue loading are analyzed,and the influencing factors are discussed.Then the calculation formula of the deflection is established.(4)Based on static load failure test of prestressed concrete beams with manufactured sand without fatigue failure,we research whether fatigue loading will affect the post-cyclic static strength,stiffness and crack.After 2.5 million times cyclic loading,the prestressed concrete beams with manufactured sand can still keep good carrying capability and intensity of non-prestressed reinforcement and prestressed strands can still fully perform.It indicates that the remaining ultimate bearing capacity of the beams is not influenced by fatigue loading progress.