Ductility analysis of prestressed steel reinforced high-strength concrete beam considering hoop-confined effect

Abstract:

Prestressed steel reinforced high-strength concrete (PSRHC) beams possess high load-carrying capacity and small section dimension, which is applicable to long-span and heavy-load buildings. To investigate the various design parameters' effects on the ductility of PSRHC beam members, the static behavior of PSRHC beam was simulated with numerical method and multi-parameter analysis was carried out. Based on the section fiber model, an analysis method, which could consider the confined effect of hoops, was firstly established to simulate the static behavior of PSRHC beams. Result shows that the analysis result has a good agreement with the test load-deflection curves. Then, the effect of parameters, including concrete class, amount of tension and compression rebar and prestress tendons, thickness of steel flange and web, and diameter and space of hoops, on the ductility of PSRHC beams was investigated. The results imply that: raising the concrete class, increasing the amount of compression rebar and hoops can improve the ductility of PSRHC beam members; increasing the amount of tension rebar, prestress tendons and thickness of steel web would decrease the ductility; and the effect of flange thickness is not obvious. When the hoop-space increases from 50 mm to 200 mm, the ductility coefficient decreases about 20.6%, and the diameter of hoop improves from 6mm to 10mm, the coefficient increases various from 18% to 34%. Finally, according to the simulation results, a regression formula, containing two parameters of hoops-volumetric ratio and complex reinforcement index, was proposed to evaluate the ductility of PSRHC members, and 3.1 was selected as demarcation value in this formula.