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Continuity

It is important to understand the relationship of strength and deflection when using multiple span profiled metal cladding, because the performance of roof cladding under load depends on the continuity over several spans.

An adjacent continuous span assists the performance of profiled metal cladding, as continuity can reduce deflection up to 50%. In single spans the cladding is free to rotate at each support, but with continuity at a support the cladding is held down by an adjacent span; reducing the rotation and midspan‑deflection.

Profiled metal sheeting deflects less over intermediate spans because it has continuity at two ends, unlike the end span, having continuity at only one end.

Continuity

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Tests for point load have established the ratio between the end span length and the intermediate span length, when both spans will fail at approximately the same load.

The end span of profiled metal cladding should be no more than two-thirds of the intermediate span for optimum performance under both point load and wind load. Neglecting to do this can lead to failure of the end spans when are they subjected to foot traffic.

The endspan condition occurs at the eaves, ridge, roof steps and on both ends of penetrations where a full width sheet is cut. Cladding around penetrations may need additional purlin support, spaced at an equal distance to the endspan spacing.

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