Ram Elements Shells FAQ
| Applies To | |||
| Product(s): | RAM Elements | ||
| Version(s): | 13.0 or later | ||
| Environment: | N/A | ||
| Area: | N/A | ||
| Subarea: | N/A | ||
| Original Author: | Bentley Technical Support Group | ||
How can I report the flexural area of steel required for shells in Ram Elements?
For shell elements that are primarily subject to out of plane bending, Ram Elements can provide output for the area of steel required in the two principal directions per ACI 318-05.
The shells must be concrete and the model must include design combos to take advantage of this feature fully. Mechanical cover for the shells should also be assigned in the Shells - Materials spreadsheet.
To see the output on screen first select the desired combo at the bottom and then use View - Stresses to see stress contours. In the list of stress options, pick As 1 or As 3 top or bottom.
To get a report of the same information use Output - Analysis - Analysis Results - and select the last option "Flexural reinforcement in shells", Be sure to select the desired combo or combos on the right and then OK.
Obviously having shells with local axes aligned to the direction of the reinforcement is critical for making this output useful.
Also note, this does not take into acount shear design norenor the effects of axial tension or comressioncompression acting on the shells.
Can Ram Elements be used to design a mat foundation on soil?
Yes, one of the keys to modeling the mat foundation is to define a regular mesh. Since the nodes of the mesh need to be supported by vertical compression-only springs, we need the mat to be manually meshed. Using a regular size mesh will help so that the tributary area of each node is fairly constant allowing you to use the same spring stiffness.
The assigned spring stiffness should be derived from the soil subgrade modulus and the average shell area. Note, the spring units are in force/length, e.g. kip/in, meaning how many kips of compression at this point does it take to yield 1 inch of deflection. To make the springs compression-only, just check the Compression only - TY box (assuming Y is vertical).
In order to insure stability some soil friction resistance or edge restraint should also be modeled. Modeling the self-weight of the foundation may also be required for stability (this can be modeled using the Gen - Self weight option). If self weight is included as part of the dead load, also make sure that the dead load is used in all of the combos. Because the model includes compression-only springs, iterative analysis is required. It may be that the model is stable for combinations, but not for the lateral load cases alone, but that's OK so long as the combos all produce valid results.
A sample file can be found here.
The method above outlines how to get steel requirements for the shells. Bearing stress results can be derived from the spring reactions.
For something a little more automated, consider Ram Concept.
See Also
Structural Product TechNotes And FAQs
External Links
Bentley Technical Support KnowledgeBase
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