FEM Simulations of Bond Behaviour between Concrete and Seven-Wire Prestressing Strand

The article deals with the subject related to numerical tests of the concrete bond to seven-wire strands. Nonlinear contact concrete-steel calculations with using Finite Element Method (FEM) is applicable for concrete bond to reinforcing steel analyses. At the moment, the analyzes are the subject of independent research projects. The research using several scientific and commercial computing systems allows us to look deeper into the sample and obtain information about cracks development, stresses, and internal deformations. Such analyzes are impossible when tests only experimentally. The concrete-steel behaviour of materials can be modeled with a bond-slip mechanism where the relative slip of reinforcement and concrete is phenomenologically described. The behaviour of the slip zone is then mapped with a zero thickness interface (contact) element. The constitutive laws of bond-slip adhesion are based mainly on the theory of total deformation, which expresses the pulling force as a function of total relative displacement. The correct construction of the bond model requires consideration of physical phenomena occurring not only at the interface of the materials but also inside within each of them. When designing numerical research, it is necessary to keep in mind the limits in computing memory of computers. Performing static calculations for complex numerical models containing a number of geometric, material and contact nonlinearities may prove to be too time-consuming on a PC. For this reason, it is now reasonable to construct approximate, simplified models. FEM models with a strand modeled as a solid bar (with a sidewall accurate to the real one) made it possible to observe and research, destructive mechanisms identified in experimental pull-out tests.