Experimental Study On Flexural Behavior Of Steel-Laminated Slabs(RC+UHPC) Composite Beams

Steel-concrete composite beams can take full advantage of the strength of steel and concrete,with many advantages,such as high bearing capacity,simple modeling,efficient construction,etc,it has been widely used in civil engineering,however,the development of steel-concrete composite beams has been restricted by the defects of normal concrete material,like low strength,large self-weight,poor durability,etc.In order to solve the above problems of steel-concrete composite beams,the laminated concrete flange combined with ultra-high performance concrete(UHPC)and normal concrete is proposed,steel-laminated slabs(RC+UHPC)composite beams(SRCU)is formed,it is a new type of structure.By the comparison with steel-normal concrete composite beams(SRC)and steel-precast UHPC composite beams(SU),the flexural behavior of SRCU composite beams was investigated in the paper.The main research work and results are summarized as follows:(1)Taking a simply supported steel-normal concrete composite beams bridge as prototype,trial designs of SRCU composite beams bridge and SU composite beams bridge were carried out,the two composite beam bridges were checked according to the Specifications for Design of Steel-concrete Composite Bridges(GB 50917-2013),and the three composite beam bridges were compared and analyzed,results show that,when meeting the design requirements,the slab thickness of SRCU composite beams bridge can be reduced upwards of 20%compared with that of the SRC composite beams bridge,the material cost of SRCU beam is 16%less than that of SU composite beams,the comprehensive economic benefit of SRCU composite beams is the best among the three brigdes.(2)On the basis of the trial designs,test models of SRC composite beams,SRCU composite beams and SU composite beams were designed and made.Experiment results show that,the failure mode of SRCU composite beams is flexural failure;provided with the approximately same flexural performance,compared with SRC composite beams,the slab thickness of SRCU composite beams can be reduced upwards of 20%compared,and the flexural capacity can be increased about 9%;compared with SU composite beams,SRCU composite beams have higher flexural capacity and flexural stiffness,the flexural price performance ratio of SRCU composite beams(flexural capacity/material cost of SRCU beam)is 1.42 times that of the SU composite beam,SRCU composite beams can relatively take full advantage of the properties of UHPC.(3)On the basis of the tests,the influence factors of flexural behavior of SRCU composite beams were studied,results show that,the reasonable range of thickness ratio of RC and UHPC is 1.5?2.3;the reinforcement ratio of UHPC is enough when meeting the construction requirement,the reinforcement ratio of RC should not be less than 0.6%;there is an reasonable ratio 0.22 between the slab thickness and the beam height,the flexural price performance ratio of the cross section(neutral axis is in UHPC)is better.(4)Calculation methods of SRCU composite beams' flexural capacity were studied,analysis show that,the simple theory of the normal composite beams can still be used for SRCU composite beams.