Experimental Study On Compressive Behavior Of Precast Concrete Columns With Cluster Reinforcement

The national "13th Five-Year" key research and development plan," High Efficiency Reinforcement and Performance-Based Design Theory of Precast Concrete Members"(2016YFC0701402),proposed a prefabricated concrete column with cluster reinforcement to reduce the number of connections between the vertical bars of the precast concrete columns and the anchorage length of the reserved bars to improve the production of the assembly structure.The efficiency of installation and the design idea of efficient reinforcement.The cluster reinforced precast concrete column refers to the rebar arranged around the column at the four corner of the column,which is composed of a number of steel bars and spiral stirrups,and the diameter of the beam is generally 100mm-150mm.However,the existing The concrete structure design code(GB50010-2010)does not specify the method for calculating the bearing capacity of the columns under normal section.Therefore,the axial compression and eccentric compression test of the prefabricated concrete column with cluster reinforcement is carried out in this paper,and the static loading test is carried out on 4 axial compression and 3 eccentric compression prefabricated concrete columns,and the stress study energy of the prefabricated concrete column with cluster reinforcement is studied.The main conclusions are as follows:In order to study the pressure behavior of the prefabricated concrete columns with cluster reinforcement,the monotonic static loading tests of 4 axial compression and 3 eccentric compression reinforced concrete columns were carried out respectively.The main conclusions are as follows:(1)The axial compression failure mode and eccentric compression failure mode of the precast reinforced concrete columns are basically the same as those of the ordinary reinforced concrete columns.The failure mode of the axial compression column is that the vertical cracks appear in the column first,then the external cluster reinforcement presses the outer drum,and the concrete is crushed.The failure modes of the eccentric columns are divided into large partial pressure failure and small partial pressure failure.When the large partial pressure is destroyed,the tensile bars yield to the concrete crushed before the compression zone;when the small eccentric compression is destroyed,the reinforced bar still does not yield when the concrete is crushed.(2)The compressive bearing capacity of the precast concrete columns of the prefabricated concrete columns is closely related to the strength grade,the reinforcement ratio and the initial eccentricity.Under the test condition,with the increase of longitudinal reinforcement ratio,the ultimate bearing capacity of axial compression and small eccentric compression increases.When the strength grade of the cluster reinforcement is HRB500,the compressive strain of the concrete and the longitudinal reinforcement exceeds 0.002,and its bearing capacity increases by 13.7%compared with that of HRB400.In eccentric compression,with the increase of the initial eccentricity,the compression bearing capacity of the positive cross section is greatly reduced.When e0/h=0.4,the compression bearing capacity of the positive cross section is 42.4%compared with that of the e0/h=0.2;when e0/h=0.6,the compression bearing capacity of the positive cross section is 74.6%compared with that of the lower compression bearing capacity.(3)The results show that the ratio of the test value to the calculated value is about 1.2 when the corresponding formula of The concrete structure design code(GB50010-2010)is used in the axial compression and the small eccentric compression.When using the corresponding formula in the concrete structure design code(GB50010-2010),the test value is lower than the calculated value.It shows that the reinforcement column of the large eccentric bundle column calculated according to the standard formula is not safe,so it is still necessary to modify and study the formula.This test is only static test,it is still necessary to carry out static test and expand the static test of eccentricity parameters,study the working mechanism and failure mechanism of the cluster reinforcement column,and put forward the design and calculation method of the system,which can be used in practical engineering design.