In the load history deflection calculations, RAM Concept separates internal restraint of shrinkage (due to reinforcement) from external restraint to shrinkage (due to stiff supports, rigid foundation, adjacent levels, etc). While internal shrinkage restraint is rigorously accounted for in the strain/curvature calculations at each cross section, external shrinkage restraint is approximated using the External Shrinkage Restraint parameter in the Load History/ECR tab of the Calc Options dialog.

The technical note, which can be downloaded here, is intended to establish an appropriate Shrinkage Restraint percentage to use for a typical intermediate concrete floor in a multi-story structure based on expected differential shrinkage and considering the restraint of adjacent floors. The study demonstrates how construction sequence and varying shrinkage rates of adjacent levels affect external shrinkage restraint and the expected, net differential shrinkage at each level. A similar example was originally presented in a webinar titled Designing for Temperature and Shrinkage Loadings in RAM Concept.

Note that calculations in the technical note apply to typical interior floor level of a multi-story structures, and the conclusions should not be extrapolated to other floors, like the roof level of the same multi-story structures or floors with unique conditions. A few other examples of floors where the following calculations do not apply and special consideration may be required include: lower levels connected to stiff foundations, podium slabs (especially those connected to basement walls around the entire perimeter), transfer plates, interior floors with adjacent levels with different slab thicknesses or geometries.

See Also

RAM Concept Load History Calc Options TN

Structural Product TechNotes And FAQs