Efficient single-step time-dependent analysis of PC structures

Abstract

This paper describes an efficient single-step method to predict the time-dependent behaviour of prestressed concrete (PC) structures due to concrete creep, concrete shrinkage and cable relaxation. A versatile tendon sub-element is first developed to model prestressing cables of arbitrary profiles. To enable accurate estimation of losses of cable forces, a new relaxation model is formulated based on the equivalent creep coefficient, which is verified to work not only in the case of intrinsic relaxation but also under various boundary conditions. An efficient single-step finite-element method is then devised for time-dependent analysis of PC structures considering creep, shrinkage and relaxation based on the age-adjusted elasticity modulus, shrinkage-adjusted elasticity modulus and relaxation-adjusted elasticity modulus respectively. The effects of creep, shrinkage and relaxation on the long-term performance of PC structures are investigated. The numerical results obtained indicate not only the accuracy of the method but also the significance of considering the interaction among various time-varying factors.