RAM | STAAD | ADINA - RAM Steel Beams [FAQ]

	Product(s):	RAM Structural System; RAM Steel
	Version(s):	Any
	Environment:	N/A
	Area:	Design
	Original Author:	Bentley Technical Support Group

How can I evaluate an existing composite beam?

Using the Process - View/Update command, select the beam in the model. Change the selected member size, set the stud number to the desired value and click Analyze. Then click Update Database when finished.

If the existing stud count is insufficient to achieve 25% composite action (or the code minimum), go to Criteria - Stud Criteria and for the last option, select to "Use Composite section properties".

Note: the program will never optimize a member with less than 25% composite action (US codes), but you can reduce the number of studs and evaluate this way.

The most common cause for composite beams that cannot achieve the minimum composite action is when the beam is acutely skewed to the angle of the deck. Thus, only a few flutes will cross the beam (or segment of the beam) limiting the total number of studs possible. Angles less than 15 degrees are treated as parallel to the beam, but the trigonometry of deck angles between 15 and 90 degrees to the beam are considered. In cases where the deck is to be split or crushed along a specific beam allowing for other spacing of studs, use the Assign - Ignore Rib Spacing command.

Can I lock or freeze all the beam designs?

Yes, once the designs are correct, use the Process - Freeze Design command to freeze the designs for some or all of the beams. This is often a good idea once construction documents for the project have been released.

The same command can be found in other modules, too.

Can I set a maximum interaction or deflection ratio other than 1.0, like 0.95?

Yes, this was added in version 17.01 and after. Refer to the release notes under "User-specified Demand/Capacity Limits", or the program manual for details.

In prior versions this was not available for steel beams, only for open web steel joists. Previously for steel beams, the best thing to do is visually inspect the interaction colors and identify any beams that are too close to the max interaction ratio for your comfort and then Update those one-by-one.

Another alternative was to pad the loads slightly or reduce the beam Fy, run the design and freeze all beams, then reset the loads and run it again. This approach would effectively over design the beams not only for strength, but for deflection as well.

Note, in version 17.03, the deflection ratio values, "L/D" were adjusted to incorporate the user defined deflection Demand/Capacity limits. As an example, this 28.88 ft (347") beam is originally shown with L/D default limits of 360 and 240 and with a 1.0 Max deflection ratio specified. The second section is for the same beam, but with a 0.9 Demand/Capacity Deflection limit specified.

Here are the two criteria used in the latter part of the image above:

Why are my composite beams being designed as non-composite members?

Beams that have been defined as composite, may be designed as non-composite for the following reasons:

Non-composite deck
Opening or exposed beam
Cantilever
No load

Non-composite deck: Composite beams will be designed as non-composite if the deck on both sides of the beam is non-composite for any portion of the beam span.

Opening or exposed beam: A beam that spans through an opening or penetration or for which there is a portion supporting no deck, such as an inset beam, will be designed as non-composite. Some times it is desired to design inset beams as composite. In order to do this, you can add a short beam from the column to the perimeter beams at an angle (say 45 degrees). Then define the slab edge so that it follows along these short beams, going out and around the perimeter column. That way, the entire beam is covered by the deck and it can be designed as composite (see below).

Cantilever: If the negative bending moment at the support of a cantilever beam is greater than twice the positive moment of the back span, the beam will be designed as non-composite. When a cantilever beam is designed compositely, the program determined number of studs should all be placed in the back-span. Note, for some codes no negative moment is allowed for composite beam design and in those cases a cantilever will always result in non-composite design.

No Load: If there is no load on the beam it will be designed as non-composite. This is sometimes a result of accidentally orienting the deck in the wrong direction such that the infill beams are not loaded.

Note: once a beam has been designed as a non-composite member, the composite flag for the beam will be set to non-composite. You have to go back to the Modeler and use the Layout - Beams - Change properties command to turn it back into a composite member.

Why does the program design uniform studs for some beams rather than segmented?

The program will always revert to uniform stud distribution if there are more than 5 segments along the length of the beam. For girders with offset supported beams this is common.

How can I limit the effective width considered for a composite beam.

In composite design the program calculates the effective width (beff) automatically based on the geometry of the framing and decking. If you need to limit the width you can place a slab penetration on one or both sides of the beam in the Modeler. The size of the penetration does not matter since penetrations have no effect on the surface loading, so I recommend something fairly small, maybe 1' square, placed near the mid-span of the beam. The distance from the edge of the penetration to the beam center line will then be used for the effective flange width on that side.

Can I turn off the pattern loading on beam cantilevers?

Regretfully, not at this time. Live loads are always considered to act on the cantilever only, on the back-span only, or on the entire beam, whichever condition provides the most conservative design for shear, bending and deflection. This is true even for snow loads which can be overly conservative. [[RAM Steel Beam Pattern Loading]] has further details.

Only dead loads are not subject to patterning.

Can I customize the load combinations used in RAM Steel Beam?

Regretfully, not at this time. The load combinations used in RAM Steel are internal to the program and cannot be modified.

See Section 10.3.11 in the RAM Steel Beam Manual for a list of combinations used for each design code.

Note that floor live load and snow or roof live loads are combined and applied as a single live load. Some building codes, such as IBC, permit a reduction (0.75 factor) for combinations including two or more transient loads. RAM Steel only uses the combination 1.0 DL + 1.0 LL (effectively, 1.0 DL + 1.0 LL + 1.0 SL). Using the reduction noted above, a load combination of 1.0 DL + 0.75 LL + 0.75 SL is permitted by code but not possible in Ram Steel. If the IBC is selected for the code for load combination generation in RAM Frame, 1.0 DL + 0.75 LL + 0.75 SL is used, however. This can cause some design differences for beams designed in RAM Steel Beam versus RAM Frame.

Can I override the unbraced length of a steel gravity beam?

In cases where you want the unbraced length to be reduced you can add brace points in the Modeler using Layout - Beams - Brace points. Alternatively adding additional short beams framing into the beam in question will brace the top and bottom flange at those locations. Use joists where you want only the top flange braced.

In cases where you want the program to use a longer unbraced length, for example where a beam is set higher than the deck in reality, set the Criteria - Design Criteria - Unbraced length so that neither deck perpendicular nor parallel to the beam braces the top flange. Since it's a global criteria it will affect all beams, however, so you might have to set the criteria this way and check the one beam, freeze the design, and then check the rest using the preferred criteria.

Alternatively, you could add a long penetration (Modeler - Layout - Slab - Slab Penetrations) along the beam covering most of the span.

How can I use a section that does not appear in the View/Update list?

The sections listed in the Steel Beam View/Update dialog box are based on those in the Steel Beam Design Table. See RAM Table Editing for details.

RAM Steel Beams [FAQ]