Study On Mechanical Properties Of Reinforced Concrete Flexural Members During Construction

The single pole early-dismantling formwork supporting system is a new kind of supporting system.It makes construction and template assembly more convenient because of no need to use horizontal bracing system to remain stably between single poles.It can further speed up the construction progress of the high-rise building and the speed of formwork turnover.A wide range of application prospects can be foreseen in the high-rise concrete structure.New casting components and support system constitute a spatial stressed system caused by the early-dismantling of formworks.However,it is the extremely concern for popularing single pole early-dismantling formwork supporting system that wether the formulas of mature concrete can be used to calculate the bearing capacity and deformation of early-age concrete members or wether the adverse iMPact can be caused on mechanical properties in the later under early-age load.Therefore,the bending properties of early-age reinforced concrete beams and mature reinforced concrete beams which is under bending load in the early age is studied in this paper.The method of finite element and experimental test are used to study influence parameters of early-age members.The main research contents are as follows:(1)The mechanical property of 10 new designed reinforced concrete beams are studied by method of third point loading,parameters of test include strength grade of concrete(C25,C30,C45)and ages(1d,1.5d,3d,28d).Using three point displacement loading to study crack development under load,failure mode,cross section strain,cracking moment,yield moment,ultimate moment,stiffness changes and the bond slip between steel and concrete on early age concrete.The results show that early age concrete beams are more prone to occur the inclined compression failure because of the low strength of concrete.(2)Continuously bending moment is loading in the early-age beams which is placed in the lab with 7 day's water conservation.The mechanical properties of 18 reinforce concrete beams is studied after pouring 28 days.This paper considered the influences of different strength grades,different age,different length of action time and different value of the bending moment for the beams.The results show that,the stiffness and the bearing capacity of the beams are not affected by the early damage with proper curing.(3)The finite element analysis model is established by the finite element analysis software ABAQUS and experimental results.And the paper pays attention to the influences of concrete strength,reinforcement ratio,hoop ratio and section size on the mechanical behavior of concrete beams and slabs in the early age.(4)To discuss the applicability of mature concrete formulas for the calculation of flexural capacity,shear capacity and cracking force.Results showed that the mature formulas of concrete beam are still suitable for early age concrete beam.What's more,putting flexural capacity formula of early-age slab with single pole supporting.To provide a reference for the calculation of early-age beam and slab structures in the single pole early-dismantling formwork supporting system.