How RAM Concept calculates envelope results

Envelope Results - Loadings

Envelope results for a loading are determined by comparing the results for the full loading and the results of all of the pattern loadings (considering the pattern factors). Envelope results consist of a subset of results which occur simultaneously with minimum and maximum values of certain resultants.

For example, for a design section, all of the pattern results would be compared, and the pattern result with the largest bending moment would become the Max M result for that design section; other design sections’ Max M results might be determined by other patterns.

If the loading is not patterned, then all of the envelope results are identical to the standard results.

Envelope Results - Load Combinations

Envelope results for a load combination are determined by comparing all the permutations of standard and alternate load factors multiplied by all envelopes for each loading in the load combination. For each location and envelope type, the chosen load factors are those that create the most extreme envelope.

In mathematical terms:

There are 2^n(p+1) results for n loadings and p patterns.
These 2^n(p+1) results are enveloped together.
The actual calculations that RAM Concept uses do not consider 2^n(p+1) load combinations, but the result of the RAM Concept ’s calculations is the same as if it did.

Envelope Results - Rule Sets

Envelope results for rule sets are determined by comparing all the envelopes for all of the load combinations that use the rule set. For each location and envelope type, the chosen values are those that occur simultaneously with the most extreme envelope.

Envelope results for a loading, load combination or rule set are all the results on the Reaction tab and Strip tab except for those with the "Standard" context. The Standard context for these plots is sometimes referred to as the "standard envelope", but technically it is not an envelope at all.

Note: RAM Concept ’s enveloping finds the critical cases in most regular and complicated models. It would be possible, however, for the six envelopes to miss the critical case. If you believe that a set of forces not included in the envelopes may be critical for the design, you can manually create additional loadings (without patterning) and/or additional load combinations (without alternate load factors) and/or additional rule sets (using a single load combination) to ensure that the force set of concern is considered in the design.