Spatial Embedded Slip Model for Analyzing Time-Relative Coupling Effects of Creep and Prestress on PC Bridges

Abstract

This paper presents, for analysis of prestressed concrete (PC) bridges, a spatial embedded slip model that is based on a three-dimensional isoparametric element, truss element, and nonthickness bond element, to simulate concrete, tendon, and the interface of the two, respectively. The bond element is embedded into the slip model via the virtual nodes introduced at the intersection points of tendon and concrete. Based on the displacement-based finite-element framework and the constitutive relations of each component, the elastic finite-element equilibrium equation for the slip model is deduced according to the virtual work principle. The quasilinear regression method is used to fit the creep coefficient in the Chinese bridge design code. Then, based on the elastic equilibrium equation and theoretical incremental formula of creep analysis, the equilibrium equation for analyzing time-relative coupling effects of creep and prestress is derived and the finite-element program is developed. The proposed model allows tendon to go through concrete in any pattern, without consideration for layout and direction of tendon and therefore with convenience in a finite-element mesh. The freedoms of the virtual nodes can be reduced in the formation of the equilibrium equation. Verified by a numerical example of a simply supported beam with a rectangular section, the embedded slip model is proved to support accurate linear and creep computation within an elastic range of materials.