טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentIssawi Lina
SubjectCoupled Nonlocal Damage-Plasticity Formulation for Modeling
Axisymmetric Concrete and Reinforced Concrete
Specimens
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Mahmood Jabareen
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

The bond between the reinforcement and the concrete is a fundamental issue in reinforced concrete. This term covers various phenomena related to the resistance against pulling (or pushing) a reinforcing unit through the concrete. The interaction between the reinforcing steel bar and the surrounding concrete is a central element in this study. It governs the stress distribution along the reinforcing steel bar and the concrete, as well as the corresponding deformations, and, as a result, produces concrete cracking or crushing at higher stress levels. It is a generally accepted view that the transfer of forces between a reinforcing unit and concrete is caused by chemical action, friction and other mechanical actions, that are activated at different stages of loading. The contribution of each of these mechanisms strongly depends on the surface texture of the reinforcement and its geometry. Bond mechanics is difficult to study experimentally since the bond stress and the slip are local phenomena that are difficult to measure. The relationship between bond stress and bond slip is not unique but varies with the loading history and magnitude of maximum slip.

In the present research, an axisymmetric higher order element was developed for describing the nonlinear behavior of the concrete under compression and tension. The developed element has eight nodes and each node has three degrees of freedom. The first two degrees of freedom are used to interpolate the displacement field, while the third one is the nonlocal damage in the concrete. It is well known that concrete is characterized by a softening behavior right after the peak stress. Such softening will lead to undesirable behavior in which the numerical solution depends strongly on the size and the shape of the finite element mesh. Therefore, the model was enhanced by adding a new scalar variable that describes the nonlocal damage in the concrete.