Assessment on effective stiffness of RC hollow columns based upon semi-static experiment

Abstract

The effective stiffness is a key parameter to assess the seismic performance and supply rational design for a column of the regular concrete structures. Due to the detail difference between the reinforced concrete (RC) hollow and solid columns, the applicability of the existing models, almost obtained from the test results of solid columns, to the hollow members should be studied deeply. The rationality of only a few available formulas from hollow specimens should be validated through experimental investigation. Therefore, the test data of 28 rectangular hollow columns in literature were selected to evaluate the existing equations for effective stiffness. To explore the nonlinear characteristics of RC hollow columns and supply more practical and rational formulas of stiffness, 7 rectangular and 5 round-end hollow specimens were tested by pseudo-static loading to clarify the critical factors of effective stiffness. The analysis on test data shows that the effective stiffness increases almost linearly with increased axial compression and shear span ratio. The quantity of rebar, strain penetration, strength of concrete and steel have little influence on effective stiffness compared with the axial compression and aspect ratio. A novel simplified formula was proposed based on the foregoing 35 rectangular hollow specimens considering the effect of axial pressure ratio, shear span ratio. The rationality and generality of the suggested formulas were verified according to the test results of five round-ended hollow specimens. The comparison analysis shows that the proposed model is more applicable than the existing formulas to assess the effective stiffness of different types of hollow columns with more precise.