Performance Of Reinforced Concrete Columns Subjected To Earthquake

Earthquake damage shows that multi-storey reinforced concrete frame tructures are prone to collapse and cause a large number of casualties under strong earthquake.So far,scholars have not yet grasped the method to control the collapse of frame structures.Several earthquake simulation tests of multi-storey frame structures show that even if the shear-span ratio of columns reaches 3,the long columns defined in the code also suffer from obvious shear failure.Three groups of columns with different shear span ratios(the shear span ratio is 3/4.25/6)were designed to investigate the causes of the failure.The pseudo-static test method was used to load the columns.It is hoped that the relationship between the shear span ratio and the failure modes of the columns will be understood in depth,so as to provide a scientific basis for the seismic design of the columns.The main results are as follows.1.Two coefficients?s and?m,reflecting failure modes and seismic capacityof columns are proposed.When the column is in critical failure state under earthquake,the ratio of maximum shear force to axial force is defined as the coefficient of shear capacity of the column when the column is damaged in shear mode;when the column is damaged in bending mode,the ratio of shear force to axial force corresponding to the critical moment is defined as the coefficient of bending capacity.When the shear span ratio of columns is from low to high,the seismic capacity of columns is first controlled by the shear capacity coefficient and then by the flexural capacity coefficient,during which there is a critical shear span ratio of?_c.2.Based on three groups of quasi-static tests of eight columns with a total of 4 1/4 ratios in each group,a preliminary?-?curve reflecting the relationship between shear-span ratio and failure mode of columns is established,which can be used to guide the seismic design of columns.3.In the test,not only the horizontal force and displacement at the end of the olumn are recorded,but also the vertical strain reflecting the bending moment at the end of the column and the oblique strain reflecting the shear of the column body are measured.Based on the measured data,the real boundary constraints at the end of the column are inverted,which provides a new method for grasping the real stress conditions of the column in the test.