Influence of concrete creep on performance characteristics of prestressed concrete columns

摘要

The main research objective in this paper relates to the theoretical and experimental analysis of a unified design and tests procedure for analytical prediction of durability and reliability structural characteristics of precast and prestressed concrete columns, subjected to long-term loads. Previous theoretical studies supported by practical experiments have shown that the use of differential equations in problem solving oriented to the field of reinforced concrete structures and specifically to prestressed concrete columns is effective to improve the stiffness of the structural material and predicting the eventual progressive cracking characteristics of the structural members. However, little evaluations of time effects provided by the stressing of high strength steel tendons, and by the long-term static loading of the structural members have been conducted. This theoretical and experimental study relates to details of a unified design and tests procedure for analytical prediction of various durability, reliability and quality structural characteristics of the columns. For structural and crack predictions, virtual work principles have been used to estimate (a) transient strains due to the concrete creep and shrinkage, (b) the resulting time-dependent stress redistribution, as well as (c) displacement variations in the columns and (d) prestressing losses in the prestressing high yield tendons. The finite-difference method based on the displacement formulation has been successfully used, to solve the systems of nonlinear equilibrium differential equations. A series of test experiments with once evaluated strength parameters have successfully been planned to provide encouraging support to numerical evaluations in the theoretical part of this present report.