Rigid Support Zones in RAM Concept

In RAM Concept, columns are idealized as point support objects, which means that column elements are assumed to support slab elements at a single point in the finite element model. Similarly, walls are idealized as line support object, which means that wall elements are assumed to support the slab at points along the wall centerline only. This differs from the actual structure, in which the slab is supported over the entire region bounded by the column shape and over the entire wall thickness.

The column and wall idealizations make the modeled structure more flexible than the actual structure. This flexibility can result in more conservative slab deflections and rotations and complicate the accurate prediction of concrete floor deflections. The differences between calculated and actual deflections increase as column size and wall thickness increase.

A rigid support zone feature was added in RAM Concept Version 8 Update 2 to better model the rigidity of slab elements within columns and wall shapes. To use this feature, edit the column and/or wall properties, check the “Mesh Slab Support Region” box, and enter an appropriate “Slab Support Region Stiffness Factor” in the Meshing tab (see Figure 1). The default stiffness value is 10, which represents the maximum factor permitted by RAM Concept and ensures a sufficiently stiff elements over the supports.

Figure 1. Column Property for Adding Meshed Support Region

When utilized, the rigid support zone feature forces RAM Concept to mesh elements within the plan area of the column elements and walls. The specified “Slab Support Region Stiffness Factor” is used as a stiffness adjustment factor for flexural and torsion for these elements. Examples showing how the meshed and properties changes when the option is checked or not checked are shown in the figures below.

Figure 2. Meshed Elements and Stiffness Properties Without Support Region Option

Figure 3. Meshed Elements and Stiffness Properties With Support Region Option