Nonlinear analysis of prestressed concrete structures under monotonic and cyclic loads

This study proposes a finite element model for the nonlinear analysis of prestressed concrete frame structures. The model is suitable for the analysis of pretensioned or posttensioned, bonded or unbonded prestressed concrete frame structures under monotonic or cyclic loads. The model centers around a prestressed concrete (PC) element that consists of three components: (a) a fiber beam-column element that describes the behavior of concrete and bonded reinforcing steel, (b) a prestressing tendon steel element, and (c) a link (bond, friction or anchorage) element that describes the transfer of forces between the prestressing tendon and the fiber beam-column element.; The fiber beam-column and prestressing tendon element are flexibility-based elements with nonlinear material characteristics whose state determination is based on an iterative solution scheme that strictly satisfies internal equilibrium and compatibility. Upon convergence of the iteration process, the nonlinear section force-deformation relation is satisfied within a specified tolerance.; The beam-column and tendon element act in parallel. They are connected at the nodes of the PC element through the link element that provides either a concentrated force transfer at the anchorage nodes or a distributed force transfer along the tendon profile through bond and friction. The anchorage element is suitable for modeling tendon anchorages in posttensioned construction. The distributed force transfer along the tendon profile through the bond element simulates the prestress transfer in pretensioned construction and the flexural bond. The friction element describes the effects of friction between the tendon and the duct during the posttensioning operation and is very similar to the bond element except that a friction stress-slip relation is used instead of a bond stress-slip relation.; The prestressing force is incorporated into the structural model through a sequence of analysis steps that are intended to simulate the post- or pretensioning operation in the actual structure. The model has been used in the analysis of different types of prestressed and reinforced concrete structures. Phenomena such as the formation of plastic hinges, the redistribution of bending moments, bond slip, the "pinching" of the hysteretic response under cyclic loads, the bond at prestress transfer and the prestress loss due to friction are successfully described by the proposed model.