A Lattice Approach for Analyzing Steel-Concrete Bond-Slip-Layer Fracture


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Title: A Lattice Approach for Analyzing Steel-Concrete Bond-Slip-Layer Fracture

Author(s): A. Vervuurt and j. G. M. Van Mier

Publication: Special Publication

Volume: 156


Appears on pages(s): 85-106

Keywords: bonding; composite materials; cracking (fracturing); failure; fracture properties; models; particle size distribution; reinforced concrete; steels; Materials Research

Date: 9/1/1995

Crack propagation in composite materials is a very complex process. Of utmost importance seems the behavior of the interfaces between the constituting phases. In reinforced concrete, interfaces not only appear in the concrete itself, but also between the concrete and the steel reinforcement. Fracture of the steel-concrete interface can be seen as a combination of adhesion, mechanical interlock, and frictional stress transfer. In this paper, steel-concrete interface fracture is modelled at the meso level. At this level, a simple linear elastic fracture law seems to suffice to explain global fracture mechanisms of composite materials. Interfaces between aggregate and matrix and between matrix and reinforcing bars are simulated using a lattice model. In the model, the material is discretized as a lattice of brittle breaking beam elements. Disorder of the material is implemented by assigning different strength and stiffness properties to the beam elements. Cracking is simulated by removing in each load step the element with the highest stress over strength ratio. The model is applied to uniaxial tensile fracture of plain concrete specimens and to bond of steel to concrete. Comparison from the simulations presented in this paper with experimental data shows that crack mechanisms are simulated quite accurately. However, the bond-displacement behavior is still too brittle. This point can be improved when more detail is included in the material structure that is incorporated in the analysis. The macroscopic bond-slip behavior of a reinforcing bar depends strongly on the micro-cracking near the interfacial zone between concrete and reinforcing bar. The analyses clearly show the influence of adhesion between steel and concrete on the simulated crack patterns.