RAMSS Beams [FAQ]

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.

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.

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.

Can I turn off the pattern loading on beam cantilevers?

Regretfully not at this time. Live loads are always consider to act on the cantilever, on the back-span 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. Only dead loads are not subject to patterning.

WhyaremybeamsbeingdesignedpertheCanadian(orBritish)codewithaDesignFy(orpy)lessthantheNominalyieldstressassignedintheModeler?

PleasereviewtheRamManagermanual,section2.4.7CanadaParameters,2.4.8BS5950ParametersandtheRamSteelBeammanualsection10.4DesignYieldStrength.

Tosummarize,Whenusingeitherofthesecodesfordesign,thesteelmaterialtypeforeachtypeofstructuralmembermustbedeterminedfromatable.Thissteeltypeiscombinedwiththenominalyieldstrengthassignedtoeachindividualmemberinthemodeltodeterminethesteelgradeandthedesignyieldstrengthofthesection.

Forexample,asectionoftypeWwithanominalFyof350N/mm2isassignedasteelgradeof350W.But,anominalFyofslightlylessthan350willresultinasteelgradeof300W.Consequently,assigningayieldstressofexactly50ksiwhileusingEnglish /Imperialunits,willresultinasteelgradeofonly300Wbeingused,since50ksi=344.7N/mm^2whichislessthan350.

SpecifyinganominalFyormaterialtypethathasnomatchingsteelgradewillresultinadesignyieldstrengthof0.0andnogradeassignment.

IntheRamManagerunderCriteria-CanadaParameters(orBS5950Parameters)wherethespecificgradeforvarioussectiontypescanalsobespecified.

Fortheexampleabove,iftheMaterialtypeA572/A992isselected,thenthebeamwillbedesignedwithaDesignFy=50ksi

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

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