As of the 2017.a version, CYPECAD allows users to assign an earthquake resistance category to concrete beams (primary or secondary), in such a way that those selected as being secondary beams are not considered as being part of the structural system that has to resist seismic action. The stiffness of these beams is reduced in the analysis and the checks carried out on them are different compared to those carried out on beams considered to be primary beams. More information can be found in the section: "Earthquake resistance category” in the new features of the 2017.a version.
As of the 2017.c version, the earthquake resistance category of floor slabs is implemented, which allows users to class the following types of concrete floor slabs as primary or secondary:
- Flat slabs (reinforced and post-tensioned)
- Waffle slabs
- Hollow core slabs
- Concrete joist floor slabs (generic, precast reinforced, prestressed reinforced, or in situ joists)
In the “Earthquake resistant category” dialogue box (“Beam definition” tab > “Slabs” menu > “Earthquake resistant category”), users can assign this category to concrete slabs. By default, any slab that is introduced has assigned the “Primary slab against seismic action” category.
Just as for concrete beams, concrete floor slabs which are assigned as being secondary are not considered to be part of the earthquake-resistant structural system. To do so, CYPECAD reduces the stiffness in the analysis of these elements in a ratio, that can be edited, which by default is 0.01. Users have two options to indicate the inertia reduction factors that are to be used in the analysis. These are located in the “Inertia reduction factors” dialogue box (“Beam definition tab” > “Project” > “General options” > “Inertia reduction factors”) and are “Based on the code” (default option) and “Specified by the user”.
