Model Setup

The design of a concrete shear wall is determined by the axial force in the wall, which arises due to applied vertical loads but also from in-plane bending, where the walls are resisting laterally applied loading. While it is frequently most convenient to obtain the forces on the core walls as part of a full model of the structure, it is also often possible to model just the core elements and apply the loads manually to the core using the various FE surface loads and/or nodal loadings, though this will require the distribution of loads within a structure to be determined.

Minor axis bending can have a significant effect on the design results for a shear wall. This can occur in a model where the concrete floors are also modelled as finite element surfaces and the slab/walls junctions are modelled to act monolithically with the core walls, with the connections between slabs and walls transferring moments. This behaviour can be altered by defining edge releases at the junction between the slabs and walls, such that the slabs then transfer vertical and horizontal forces to the core structure, but the slab edges are acting as pinned in terms of the edge rotation.

Where the slabs are intended to act monolithically with the walls, the application of Stiff Regions are frequently helpful in terms of the forces on the slabs, but they generally will tend to have a minimal effect on the results for the wall portion.

An area of particular interest in terms of the model set up is the support conditions are the base of the wall. While the support condition will, in most cases, have a minor effect on the forces in the wall remote from the support, the force distribution in the walls at the base level can be significantly affected by the support set up. Modelling the support conditions are nodal supports at the ends of the walls can, for example, induce very high axial forces in the ends of the walls and induce a zone of significant horizontal tension where the base of the wall attempts to span horizontally as a very deep beam, and so give a significantly different design from a wall that is continuously supported at the base level.