Analysis of anchorages in concrete using a plastic-damage model

This paper is a study of anchorages in concrete which are loaded until the concrete fails. A major difficulty in the design of such structures is to determine the concrete bearing capacity and the damage under ultimate loading. This becomes more crucial when the design is limited by structural or cost considerations. Hence field tests and numerical analyses are necessary to ensure reliability and safety.

Based on continuum plastic and damage theories, a new constitutive model is developed to capture the salient features of the behavior of concrete, including volumetric sensitivity, plastic hardening, strain softening, and post crushed behavior. The study is concentrated on formulating the equations which model this plastic process including anisotropic damage. Damage is accompanied by strain softening along with highly nonlinear deformation. and high strain gradients. A set of material parameters is determined using existing experimental data in several types of loading.

The finite element predictions with the plastic-damage model reveal the structure of the deformation field surrounding the embedment and the development of damage areas in the concrete. The numerical results simulate several field tests on particular types of anchorage structures, such as a short anchor under shear and pullout tests. The highly nonlinear load-displacement curves observed in tests are reproduced, while comparisons of numerical predictions and experiments give reasonable results.

The principal finding of this study is that a considerable safety factor can be achieved in anchorages in concrete if embedded reinforcing arms are attached to the anchorage to spread the load.