When defining reinforced or prestressed joist floors (in the "Enter floor" window), if the "By geometrical properties" option is selected, users must choose the "Selected floor slab" from those available in the project.

The controls on the right allow you to "Add", "Delete", "Copy" or "Edit" these floor plans. It is also possible to access a "Library Manager" options menu to save information about the defined sections to files on the hard drive.

When you use these controls, the program opens a window where you can configure each joist floor slab according to its geometric properties.

Here, a "Reference" is first entered for the floor slab.

Next, the "Geometry" is defined by entering the following parameters:

• the "Compression layer thickness (a)";
• the "Form depth (b)";
• the "Rib spacing (c)" between joists;
• the "Rib width (d)";
• the "Longitudinal width" of the form, which only affects the quantities of forms carried out in the "Form quantities report" (menu "File > Reports > Form quantities");
• and the "Rib width increment" or thickness of the ribs of the small form to be taken into account for the purposes of calculating deflection.

The first parameters (a, b, c and d) refer to the distances shown in the floor plan diagram displayed in the centre of the window.

The "Calculation data" is defined below:

• The "Concrete volume" checkbox can be activated or deactivated:
  • If this option remains deactivated, the program calculates the approximate volume of concrete per unit area, taking into account the geometric parameters entered in this window, and displays the updated value in the field on the right.
  • If this option is activated, users can enter the concrete volume per unit area in the field on the right; this value may differ from that suggested by the program, thereby overriding it.

• In the drop-down menu "Vault type", select the vault material. This can be:
  • Concrete / Ceramic / Polystyrene
    In these cases, this information, together with the geometric parameters entered, allows the approximate "Surface weight" of the floor slab to be calculated for both single and double joists. These values are shown on the left.
  • Generic
    Alternatively, you can select the "Generic" option to manually enter the surface weight of the floor slab with simple joists in the field provided on the right.

• The last drop-down menu indicates whether the "Deflection check" that the program carries out on these floor slabs is carried out for reinforced joists or prestressed joists, which affects the calculation of the cracked moment of inertia of the joists:
  • As a reinforced joist
    In the case of reinforced joists, the program calculates the amount required to support the positive moment in the joist. Using this value, it calculates the approximate cracked moment of inertia.
  • As a prestressed joist
    In prestressed joist floors, the approach used for reinforced joists is not applicable, as the behaviour of this type of joist is entirely different; it may be the case that the cracked moment of inertia is practically equal to the gross moment of inertia due to the effect of prestressing. Therefore, in this case, the user must enter the value of the "Cracked stiffness" expressed as a percentage of the uncracked stiffness ("% gross stiffness") in the field on the right. This percentage ranges from 50% to 100% in the most common cases found in manufacturers’ data sheets.