What can RAM Concept design?

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

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. The RAM Concept manual contains a section “Decreasing calculation time” that contains more detailed information on this topic.

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

RAM Concept's analysis of slab elements considers shear deformation as well as bending deformation. This ensures that RAM Concept gives reasonable results for both thin slabs and thick slabs. In general, RAM 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 (e.g. a thick grade beam), 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 RAM Concept be used to design Pan Joists?

You can certainly model and design T-beams with the program.

We do not consider any of the code specific provisions for repeated joists (e.g. reduced shear requirements), nor is there any way to consider a T-beam with a tapered stem.

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

Yes. This can be accomplished with the strip wizard feature. The RAM Concept manual contains chapters entitled “Using Strip Wizard” and “Strip Wizard Tutorial” that address this feature.

Can I model a pour strip?

Yes, although there are limitations.

1. It is often desirable to use orthotropic properties for the pour strip area such that the axial stiffness across the strip is significantly reduced. 

2. Terminate tendons either side of the pour strip. It's best to extend the tendon dead ends a very small distance into the pour strip, and generally these terminations should be at slab mid-depth.

3. The span segment design strip should be segmented at the pour strip edges. Be careful that the end of the design strip is not beyond the end of the tendons. The second pour strip segment of the design strip should not be considered as post-tensioned (General tab of span segment properties)

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

While RAM 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 RAM 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 RAM Concept's design cross section reports all of the moments and forces on the design cross section, RAM Concept does not perform design considering all of the forces and moments. Specifically, RAM Concept does not consider the Mz value in design, because RAM Concept does not specify the positioning of reinforcement that is important for Mz design. RAM Concept does not consider “P-Delta” effects.

What does “hybrid” mean?

A hybrid floor is one that contains both post-tensioned (PT) and reinforced concrete (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

RAM Concept Structure FAQ

Structural Product TechNotes And FAQs