What can Concept design?

Elevated (suspended) concrete floors and mat foundations (rafts). They can be reinforced concrete, post-tensioned concrete or hybrid.

Is there a limit on the size of structure modeled?

The only limit is the performance of the computer hardware. The analysis run time is approximately proportional to the square of the number of nodes in the model, so large structures may take a significant amount of time to analyze. Design time is approximately proportional to the number of span segment strip cross sections. See “Decreasing calculation time” on page 128 for more information.

Is there any restriction to the maximum thickness of slab that can be modeled?

Concept's analysis of slab elements considers shear deformation as well as bending deformation. This ensures that Concept gives reasonable results for both thin slabs and thick slabs. In general, Concept's design provisions apply the code requirements that are appropriate for slabs with typical span-to-depth ratios. If the geometry of your slab is outside the usual ranges, you may need to consider if any special design considerations are necessary.

Can Ram Concept model a sloped slab or one that tapers in thickness?

No, You can model steps in Ram Concept, but each slab and beam is a level member of a single thickness.

Can Concept design more than one story at a time?

Not by itself. You can use the RAM Structural System to integrate numerous floors into one large model.

Can I use Concept to design slab-on-ground?

The expression “slab-on-ground” is often used to described residential house slabs. The designer has to use engineering judgment to determine if mat analysis and design techniques are suitable for such structures.

Is Concept capable of running a single design strip for quick preliminary runs without modeling the whole building?

Yes. See Chapter 35, “Using Strip Wizard” and Chapter 45, “Strip Wizard Tutorial”.

Can I model a pour strip?

Yes, although there are limitations.

1. Use the orthotropic properties for the pour strip area such that the axial stiffness perpendicular to the strip is signifi¬cantly reduced. See the discussion below Figure 16-6 on page 57
2. Terminate tendons either side of the pour strip.

Note: Modeling a pour strip in this manner does not consider the temporary situation before the strip is poured back. This could affect deflections and resultants.

How can I model curved edges or walls?

Use a series of straight lines. The approximation should have negligible effect.

Can Concept be used to design retaining walls by drawing the wall as a slab?

While Concept is not optimized for this use, it can perform most of the analysis and design tasks if you are very careful. Care must be used as Concept assumes that gravity loads are in the downward Z direction. You need to set all of the self-dead loading load factors to zero and create your own self-weight loadings. You probably want to apply these loads at the mid-slab depth; otherwise the eccentricity will add a self-weight moment to the slab. While Concept's design cross sections reports all of the moments and forces on the design cross section, Concept does not perform design considering all of the forces and moments. Specifically, Concept does not consider the Mz value in design, because Concept does not specify the positioning of reinforcement that is important for Mz design. Concept does not consider “P-delta” effects.

What does “hybrid” mean?

A hybrid floor is one that contains both PT and RC areas. Most post-tensioned floors have some RC elements such as pour strips and elevator core slabs. By selecting the appropriate design rules these regions can be designed at the same time as the PT elements.

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

Comments or Corrections?

Bentley's Technical Support Group requests that you please confine any comments you have on this Wiki entry to this "Comments or Corrections?" section. THANK YOU!