What STEELSOFT calculates

STEELSOFT is design software for steel connections to EN 1993-1-8, focused on fixing sheet and cladding: bolts, nuts and self-drilling screws through thin layers. It is intended for structural engineers, envelope and sheet-metal roof designers, and cladding manufacturers.

What sets it apart is that it describes the connection as a stack of layers, not as two sections meeting. It asks for the thickness of each layer separately, for the pilot hole and for the sealing washer, and picks a suitable fastener automatically. This is a tool for thin sheet connections — as distinct from ConSteelSoft, which handles structural beam-to-column connections.

The connection layers

The layers module is the heart of the software. It defines the application type, the grade of the sheet being fixed, the material, the thickness of the first layer t₁ and the thickness of the second layer t₂, the pilot hole and the clamping thickness, and the EPDM sealing washer.

This is the resolution thin sheet demands. The two layers are not handled as one thickness: t₁ and t₂ are entered separately, the pilot hole is defined in its own right, and the EPDM washer is not merely a sealing accessory but part of the system that enters the calculation. The clamping thickness too — the part that is not clamped — is a field of its own and not a derived value. The grade of the sheet being fixed is entered alongside them, because in cladding the sheet itself is part of the connection and not just the thing being fixed to.

Protection level and exposure environment — ISO 9223

A separate module defines the required protection level and the exposure environment to ISO 9223. In cladding connections this is usually the real failure condition: the fastener does not break under load, it is eaten away by the environment it was put into. The ISO 9223 exposure classification translates the location of the structure into a protection requirement, so that the choice of fastener is not based on strength alone.

The materials — aluminium, stainless steel and steel

The software works with three material families and asks each of them for what governs the design: aluminium alloy with f₀ and f_u alongside the aluminium product form, stainless steel grade with f_y and f_u, and steel grade.

In aluminium the distinction matters most of all — the design rests on f₀ rather than on a classic yield point, and the product form changes how the material behaves around the hole. The tool does not roll the three families into one material with a correction factor.

Hole type, friction class and profile shape

These modules define the hole type, the friction class and the profile shape. The hole type and the friction class are what decide whether the connection works in bearing or in friction — that is, whether it is designed to slip under load or not. The profile shape decides what there is to screw into in the first place, and at what angle.

Automatic plate, bolt layout and loads

The automatic plate module generates a plate matched to the bolts, and the bolt layout module defines their arrangement. Loads are entered as design values (Design), and the project details module defines the connection zone — so that the calculation is identified with the place in the structure it belongs to.

On the basis of all this the software selects the fastener automatically. That is the reverse of the usual route, in which the designer picks a bolt from a catalogue and then checks whether it passes: here the conditions are the input, and the fastener is the result.

The output is a full calculation report to EN 1993-1-8 covering the automatically selected fastener, the connection layers with t₁, t₂, the pilot hole, the clamping thickness and the EPDM washer, the protection level and exposure environment to ISO 9223, the materials and their grades with f₀/f_u or f_y/f_u, the hole type and friction class, the profile shape, the plate and bolt layout and the loads — alongside the project details and the connection zone.