Downstand beams can significantly influence the reinforcement needs of the parent slab. Different software packages have varied approaches for modeling these beams. In Prokon SUMO, the workflow involves defining the beam’s width, depth, and, finally, adjusting the offset to accurately model it as a downstand beam.
In contrast, Robot Structural Analysis Professional (RSAP) simplifies this process to a single parameter within the beam’s properties. By default, a beam is modeled in a standard position.
To adjust this, select the beam, and its properties will appear on the left-hand side of the interface. In the properties panel, locate the “Offsets” row, which is highlighted in blue. Clicking the N/A cell allows you to choose either Lower Flange or Upper Flange. Selecting Lower Flange models the beam as an upstand, while choosing Upper Flange models it as a downstand.
Does this adjustment impact the analysis? Absolutely! Consider a model with a 50 kPa slab load, duplicated into two versions: one with the beam offsets set to Upper Flange (downstand), and another left unchanged. The results showed that the maximum deflection was -141.3 mm for the model with downstands, compared to -255.8 mm for the model where the beams remained in their original position.
This demonstrates that adjusting the offset is well worth the minimal effort, as it can yield substantial improvements in structural performance.
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