Kamran M. Nemati's Research Interests


Pull-Out-Induced Cracks In Reinforced Concrete


The purpose of this investigation is to clarify some of the mechanisms and phenomena relevant to description of the debonding process between deformed reinforcement and concrete.
The molten metal injection technique for accurate identification of cracks under load down to microscale, is considered to be the best possible solution for identification of the complicated pull-out induced crack patterns in reinforced concrete. Using this experimental technique, it is possible to investigate crack patterns and crack widths, and to study the process of creation of different types of cracks by investigating the crack patterns at different stages of pull-out. For instance, it is possible to study in detail the interaction between cone-shaped and longitudinal splitting cracks.

Figure 1: (a) Pull-out of a reinforcing bar from a concrete specimen. (b) Local pull-out of a reinforcing bar in a beam exposed to bending.

Further, it is the intention of this research to model the rebar pull-out cracks using a finite element model. The model includes formation of cracks, and geometrical nonlinearities to describe the expected nonlinear interaction between cone-shaped cracks and splitting cracks.

Figure 2: Internal cone-shaped cracks and longitudinal splitting cracks.

Computational models will be established for pull-out crack phenomenon in reinforced concrete to support the experimental research. There are two finite element programs available for this research: DIANA and S-Beta. The tension-pull configuration will be modeled as center-placed reinforcing bar protruding from a concrete cylinder. The reinforcing bar will be modeled as four-node rectangles and in order to minimize the directional bias, the concrete phase will be modeled with three-node triangles in a cross diagonal pattern.

Figure 3: Computational set-up to investigate bond-slip cracks in pull-out test


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Send email: nemati@ce.berkeley.edu