THE PRECISION-CONTROLLABLE GENERAL APPROACH TO ANALYZE TIME-DEPENDENT EFFECT IN PRESTRESSED CONCRETE STRUCTURES

A precision-controllable general approach (PCGA) to analyze time-dependent effect in prestressed concrete structures is presented by using finite element method (FEM) and automatically step-up method (ASUM). In this approach the FEM is only used to calculate elastic responses in which the time-related influences are not considered, while the ASUM is only used to calculate time-dependent effect due to creep and shrinkage for structures under free-constraint, thus the control of computation precision for general approach is fulfilled through precision control of FEM and ASUM, respectively. In this paper a novel built-up beam element including the effect of concrete, prestressed steels and non-prestressed steels is established, and its stiffness is adjusted by the time-dependent modulus of concrete and incessantly tensioned steels. By adopting the unified method to calculate stress distribution along prestressed steels just after anchorage is set up, the general approach can easily calculate the structural elastic response caused by each tendon, which is the base to analyze precisely the time-dependent effects in prestressed concrete structures. The discussion on theoretical values given by PCGA and current frequently used methods and tested data shows that PCGA can achieve agreeable precision.