Experimental Study On Shear Bearing Capacity Of Precast Truss Steel Reinforced Concrete Columns

As a new type of structural form,the prefabricated truss-type steel reinforced concrete structure can reduce the on-site workload,save the use of formwork and effectively save traditional building materials,so it is more extensively applied.Column is the key weighted part of structure,and its mechanical behavior will directly affect the safety of structure.Therefore,it is particularly important to study the mechanical behavior and design method of prefabricated truss-type steel reinforced concrete columns.In this paper,based on combining with National Natural Science Foundation Project Research on Mechanical behavior of Prefabricated Pre-stressed Truss-type Steel Rib Frame,seven prefabricated truss-type steel reinforced concrete column components are designed for testing the shear bearing capacity of columns.The main research work and achievements are as follows:1.The shear bearing capacity of prefabricated truss-type steel reinforced concrete columns was tested by simply supported beam method.The test parameters include shear span ratio,axial compression ratio and web member spacing.The influence law of above parameters on the shear bearing capacity of prefabricated truss-type steel reinforced concrete columns was experimentally studied,and the mechanical behavior of prefabricated truss-type steel reinforced concrete columns under combined action of pressure,bending and shear loads was analyzed,such as the development of concrete strains and the distribution of cracks,changes in load deflection of components,changes in angle strain,etc.The test results showed that the shear bearing capacity of prefabricated truss-type steel reinforced concrete column decreases with the increase of shear span ratio and web member spacing,while it increases with the increase of axial compression ratio.2.A finite element model of prefabricated truss-type steel reinforced concrete column under simply supported beam loading was established.This model considered the influences of factors such as non-linearity of material and geometry,and the interaction between steel frame and concrete.The comparison of fracture distribution,failure modes and ultimate shear bearing capacity of simulated and experimental components indicated that this finite element model is more reliable.This model was used to analyze the influence law of concrete strength and stirrup ratio on the shear bearing capacity of prefabricated truss-type steel reinforced concrete columns.3.Based on the experimental results of prefabricated truss-type steel reinforced concrete column and finite element model analysis,the shear bearing mechanism of prefabricated truss-type steel reinforced concrete column was meticulously analyzed.According to the experimental and numerical simulation results combined with theoretical analysis,a shear mechanics model of prefabricated truss-type steel reinforced concrete column was established,and the calculation formula for partial shear bearing capacity of prefabricated truss-type steel reinforced concrete column other than the axial pressure was given.Meanwhile,by referring to contribution of axial pressure part to shear bearing capacity in Design Code for Concrete Structure,a calculation method for the shear bearing capacity of prefabricated truss-type steel reinforced concrete column was built.This calculation formula expressed the contribution of concrete,angle webs and axial force to shear bearing capacity.In addition,directing at the prefabricated truss-type steel reinforced concrete in this paper,this formula can provide reference for designers.