For the seismic analysis of the structure, the program allows slabs of the following types of concrete floor structures to be classified as primary or secondary in terms of their role within the earthquake-resistant system:

• Unidirectional concrete joist floors (standard, precast reinforced, precast prestressed, or cast-in-situ, and floor systems).
• Lightweight slab floors (or hollow-core slab floors).
• Waffle slabs
• Flat slabs (reinforced and post-tensioned) and lightweight slabs.

To do this, use the "Earthquake-resistant category" option under the "Beam input" tab in the "Panels" menu.

In the dialogue box that appears, select one of the following options:

• Primary panels against seismic action
• Secondary panels against seismic action

By default, any panel added is assigned the "Primary panels against seismic action" category.

The "Assign" button allows you to select the panels to which the selected condition should be applied one by one, whilst "Assign to all" applies the selected condition to all panels on the floor. The "Finish" option closes the dialogue box.

The program uses a colour-coding system to indicate the status assigned to the various sections on the floor plan.

Concrete floor slabs classified as secondary are not considered part of the structural system for resisting seismic forces.

To this end, the stiffness of the secondary panels for seismic loadcases is reduced in the calculation based on the value defined in the "Inertia reduction factors" dialogue box (under the "Project > General options" menu). By default, this value is 0.01.