Coupling beams in shear walls can be modeled using Frame elements or Wall elements. There are three main categories for shear wall modeling:
- Deep coupling panels
- Slender coupling beams
- Moderately deep coupling beams
Deep coupling panels
Deep coupling panels are most likely to be controlled by shear. See Figure 1 below for typical panel configurations.
Figure 1: Deep Coupling Panels
Points to consider
In Figure 1(a) the floor slab is at the top of the panel, and the panel can be modeled using a single wall element. In Figures 1(b) and 1(c) the floor slab is within the depth of the panel, and there is a line of nodes at the floor level. The panel can be modeled using two wall elements, as in Figure 1(b). Alternatively it might be possible to use only a single element, as in Figure 1(c). This last model is not recommended as it may increase the band width of the structure stiffness matrix, and hence may increase the analysis time.
With the models in Figure 1(a) and 1(c), the shear strain in the wall element can be used as the demand-capacity measure. For the model in Figure 1(b) it may be necessary to use a Shear Strain Gage element that covers both wall elements.
The wall elements also have axial and bending stiffnesses, in the vertical and horizontal directions. For vertical axial and bending effects it should be reasonable to use an elastic cross section. For horizontal axial and bending effects the cross section is automatically elastic (assuming that the wall element is oriented in the usual way). One concern may be that the axial and bending effects
may artificially stiffen the piers, particularly if a pier is cracked in tension. To be conservative, it might be wise to make the axial and bending stiffnesses small (possibly very small) by specifying small elastic moduli, so that there is no stiffening effect. An alternative is to use a General Wall (rather than Shear Wall) element, and to specify fiber sections both vertically and horizontally, to allow cracking in tension. Still another option is to use an Infill Panel element, which has only shear stiffness and no axial or bending stiffnesses.
Slender coupling beams
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Moderately deep coupling beams
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