Experimental Study On Positive Moment Bending Resistance Of Simply Supported To Continuous Beam Connected With UHPC At The Flange In The Negative Bending Moment Region

To solve the problem of concrete cracking caused by tensile stress at the negative bending moment of the fulcrum of the continuous beam bridge,an experimental study was conducted on the flexural behavior of a continuous two span T-beam structure connected with ultra highperformance concrete(UHPC)at the flange position in the negative bending moment region.UHPC material was used for the flange plate in the negative bending moment zone,and its excellent mechanical properties and durability can replace the prestress in the negative bending moment zone of continuous beams,which can solve the problem of difficult control of prestress loss and greatly simplify the construction process in the negative bending moment zone of continuous beams.Due to the higher manufacturing cost of UHPC materials compared to ordinary concrete,UHPC was only poured in the negative bending moment zone flange plate,and the middle support reinforcement section was still poured in ordinary concrete.To investigate the flexural performance of the continuous beam structure in the positive bending moment zone and the influence of UHPC connection length on the flexural performance of the continuous beam,experimental research was conducted on its mechanical performance in the positive bending moment zone.Three experimental beams were simulated and analyzed using the finite element analysis software ABAQUS.Parametric analysis of the flexural bearing capacity of continuous beams was carried out by changing the strength of concrete,prestressing force,and steel reinforcement.The research results of this article are as follows:(1)The three test beams all suffered bending failure.This new type of UHPC concrete continuous beam can fully utilize the tensile properties of UHPC and avoid the beam cracking problem caused by the tensile stress in the negative bending moment region of the continuous beam.(2)Based on the verified accurate model beam,the variation of the flexural bearing capacity of continuous beams with different UHPC connection lengths is analyzed.Increasing the connection length of UHPC can enhance the flexural bearing capacity of continuous beams,but when the UHPC length reaches 2500 mm,the flexural bearing capacity of continuous beams no longer increases with the increase in UHPC length.(3)The strength of concrete has a significant impact on the cracking load of continuous beams.The prestressing only affects the yield load and ultimate load of the test beam.The strength of steel bars only affects the ultimate load.Combined with the orthogonal experimental method,the degree of influence of three factors on the bearing capacity of the test beam is as follows: prestressing force>steel bar strength>concrete strength.