The Extended Finite Element is innovative method used for treatment the discontinuity problem that faced the FE model during cracking process. Still a problem raises when the concrete is reinforced since the reinforcement rebar act as a tension stiffener when the path of crack crosses it.
There are many methods to simulate cracking of concrete in a r.c. members when using the FEM:
1. The reinforcement is treated as a smeared layer within the element and this is usually done in slabs, plates and shells;
2. The bars are embedded in the concrete elements at any location or direction;
3. The bars are simulated as two dimensional elements extending between nodes that are common with concrete elements.
The cracks are initiated where the stress or strain in concrete exceeds the specified value and the element stiffness matrix has to be modified accordingly by deleting the direct stiffness and reducing the shear stiffness.
If you simulate the rebar as a discrete link elements, you will have no problem. The crack will propagate through the concrete area or solid elements according to the stress and deformation states.
Alaa
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