Design FAQ

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Why are strip moments not the same as design moments?

Answer: Strip moments only include the integrated flexural moments m11 and/or m22, while design moments include twisting  moments as required by the Wood -Armer technique and explained in Chapter 6 of the "SAFE Key Features and terminology" manual.

Does SAFE check one-way shear in two-way slabs?

Answer: Yes, the software does check one-way shear in two-way slabs. This check is based on design strips, and follows a procedure similar to that for beam shear design. One-way shear results are available through Display > Show Reinforcement > Display type change to shear reinforcement.

Why are results distorted when strip and local axes do not align?

Extended Question: When strip direction does not align with the local axis of meshed objects, results are inconsistent. How does SAFE compute forces?

Answer: When design strips do not align with the area axis, forces are transformed to coordinate with the strip axis. If results become distorted, rotate the area axis such that it is parallel to the strip axis.

What is the best value for Max Averaging Width during Finite-Element Based slab design?

Answer: Max Averaging Width is a user-defined value which should be based on engineering criteria. When this option is selected, the software averages reinforcement design according to the peak values of similar sign which occur at increments of maximum width. As a result, the average amount of reinforcement will increase as average width decreases, whereas a large average width will produce results which are comparable to those generated without the Max Averaging Width option.

Is the slab reinforcement ratio applied to regions of variable thickness, including drop panels?

Answer: Yes, minimum reinforcement ratio is applied to all slab areas which will be designed, including drop panels.