Experimental Study On Mechanical Behavior Of Hrb500 Rebars Shale Ceramsite Lightweight Aggregate Concrete Composite Beams

Shale ceramsite lightweight aggregate concrete has light weight,high strength,good durability and seismic performance.HRB500 rebars has high strength.The application of HRB500 rebars and shale ceramsite concrete to the composite beam can effectively reduce the number of rebars joints and the weight of the components.Meanwhile,It is convenient to transportation and assembly.It can improve the construction efficiency of the prefabricated concrete structure to a certain extent.Experimental study on the flexural behavior of eight shale ceramsite lightweight aggregate concrete beams and three cast-in-place concrete beams with HRB500 overlapping hoops and longitudinal rebar were carried out.The shear performance comparison experiments were carried out on four HRB500 reinforced shale granitic lightweight aggregate concrete composite beams with with U shape stirrups without overlapping layers and four comparison beams with traditional closed stirrups.The main conclusions are as follows:(1)The HRB500 reinforced shale ceramsite lightweight aggregate concrete composite beam is similar to the failure mode of the cast-in-place beam,and no failure occurs along the laminated surface.The plane section assumption of the beam normal section is still applicable.The two types of composite beams designed to reduce the density of joint bars are similar to those of ordinary composite beams.(2)The flexural capacity,cracking load,short-term mid-span deflection of the composite beam can be calculated according to the current specification JGJ12-2006 "Technical specification for lightweight aggregate concrete structure".According to the American ACI 318-14 specification,the bending capacity of the normal section and the calculated values of the mid-span deflection are in good agreement with the experimental values.The calculation of the cracking load and the maximum crack width calculation accuracy is poor.(3)HRB500 rebars shale ceramsite lightweight aggregate concrete composite beam and cast-in-place beam have large deflection under normal use conditions.It is recommended to strengthen the check calculation when designing.(4)The short-term maximum crack width of the composite beam and the cast-in-situ beam is generally larger than the test value according to the formula.The formula in the specification is modified in this paper.The calculated value of the short-term maximum crack width of the modified formula agrees well with the experimental value.(5)It is recommended that the design strength of HRB500 rebars used as stirrup in shale ceramsite lightweight aggregate concrete beam is 360 MPa.The shear capacity of the oblique section of HRB500 reinforced shale ceramsite lightweight aggregate concrete without laminated stirrups with U shape stirrups is lower than that of the beams with traditional closed stirrups.The reduction factor ? of the bearing capacity of the oblique section considering the form of the stirrup is introduced,and the recommended value ? is 0.76.