ETABS provides for the modeling of panel zones and rigid offsets. To demonstrate, the steel-frame system, shown below, is subjected to a 10-kip lateral load along its top level. Panel-zone and rigid-offset conditions are modified for comparison.
Figure 1 - Model 1
Maximum deflection: ∆x = 0.133in
Model 1 is the most simple in that it utilizes neither panel zones nor rigid offsets. Model 1 deflections are the largest (most conservative) and moments are the smallest (least conservative).
Figure 2 - Model 2
Maximum deflection: ∆x = 0.104in
Model 2 implements fully rigid offsets at beam and columns. This technique is not recommended because the smallest and least conservative deflections result. Further, moment values are the highest and most conservative.
Figure 3 - Model 3
Maximum deflection: ∆x = 0.152in
Rigid zones are not specified for Model 3, though panel zones are introduced according to column properties. Flexibility is duplicated at joint locations, causing unrealistically large deflections. This technique is also not recommended because moment values are unconservative.
Figure 4 - Model 4
Maximum deflection: ∆x = 0.128in
Model 4 utilizes both features by modeling fully rigid offsets at beam & columns while explicit panel zone assignments are based on column properties. Here, flexibility at joint locations is correct and accurate. We recommend using this approach because it is the most realistic, as indicated by response, in which deflection and moment are within the extreme bounds.