All building authority approvals for liner tray profiles regulate the conventional design of a double-skin construction, whereby the outer skin consists of trapezoidal profiles that are directly connected to the narrow liner tray top flanges.

In recent years, designers have been demanding horizontally or diagonally arranged corrugated profiles.
In these cases, an additional spacer construction is arranged between horizontal liner tray profiles and horizontal corrugated profiles at distances between 800 and 1500mm made of Z or top hat profiles.

This type of design is not covered by the building inspectorate approval, as the spacer profiles have larger distances than the maximum horizontal distance of the connecting means between the trapezoidal profile and the liner tray specified in the approval or the load tables.

The reduced stiffening compared to the approval specifications reduces the load-bearing capacity of the liner tray profiles.

Such special designs must be dimensioned in each individual case by an experienced structural engineer. In addition, an expert opinion must generally be obtained, e.g. from the University of Karlsruhe.

The costs for a verifiable statics amount to between €1,000 and €2,000, depending on the expenditure, plus the costs for the expert opinion of about €400. Such special designs should best be clarified at an early stage with the responsible building inspection office or test structural engineer.

Netphen, July 2001

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