CREEP AND SHRINKAGE ANALYSIS OF REINFORCED CONCRETE FRAMES BY HISTORY-ADJUSTED AND SHRINKAGE-ADJUSTED ELASTICITY MODULI

摘要

Consideration of the time-dependent deformations due to creep and shrinkage is often necessary to ensure satisfactory behavior of complex concrete structures. The stresses and deformations of a reinforced concrete frame can be analyzed by the finite element method using time integration. However, as the full stress history prior to each time interval considered is necessary, with the increase in the number of time intervals used, the amount of computations increases dramatically. The concept of age-adjusted elasticity modulus is further explored to develop new functions for efficient evaluation of time-dependent behavior of concrete frames. The history-adjusted elasticity modulus is devised so that stage construction can be modeled more accurately. Likewise, the shrinkage-adjusted elasticity modulus is introduced to enable shrinkage analysis to be carried out using one single step. The methods can cope with frame structures built and loaded in several stages. Accurate results can be obtained by considering just a few large time intervals instead of those fine time steps used in time integration. Numerical examples are presented to demonstrate the usefulness of the new methods.