Product(s):	RAM Structural System
	Version(s):	13.00.00.00 or later*
	Area:	Analysis; Modeling

Problem

Missing or incorrect loads on perimeter beams, or excessive loads on the first interior beams.

Explanation

Since the advent of free form slab edges in RAM Structural System, there have been a some framing and slab edge configurations that can lead to missing gravity loads on the perimeter beams, and usually some excessive load on the next interior beams.

In the image below, the slab edge is very slightly skewed to the perimeter beam, and crosses it at one point. Consequently beam 8 is assumed to be outside of the slab edge and will not receive loads from the one-way deck. beam 14 receives all the load from the deck west of it instead.

Another situation that can cause problems is a perimeter where the beams perpendicular to the edge all cantilever out but there is no perimeter member between the cantilevers defined. In this case, the cantilevers won't be loaded by the deck as intended and the load will be applied to the supporting girder instead.

Small gaps in the perimeter framing can also cause problems.

Avoidance

The best way to avoid the problem when using one-way decks is to align the slab edge with the perimeter beams and use at least a 1" outboard overhang. Using the Layout - Slab - Slab Edge command with the "Whole Perimeter" option is a fairly reliable way to make sure the deck is aligned to the perimeter framing.

Furthermore, make sure the perimeter framing creates a closed loop around the diaphragm. 

Starting with version 15.11 we enhanced the Ram Modeler - Integrity - Data Check (Gravity) to check for some of these conditions and give warnings when the slab edge is slightly divergent from the associated perimeter framing or set 0" away. See V15.11 Release Notes.

See Also

RAMSS Common Framing Table Errors

[[Failed to Create Slab Edge load Polygons]]

[[Effects of Changing Deck Type]]