Edges in Membrane Structures


The edge is the outer boundary of the membrane panel which transfers the loads of the membrane into the primary structure. The edge can either be flexible when spanning between two corner details or rigid when directly clamped on below construction.


Key Facts

Flexible edges are curved boundaries spanning between two fixed points. In general a cable or belt is reinforcing the membrane edge and transfers the membrane stresses into the corners.


When using a cable this element is integrated inside a cable pocket. The cable pocket is fabricated out of the membrane material as a strip, folded longitudinally and then welded at the outer boundary of the membrane panel to allow a cable to be inserted. The pocket size should allow to move in the cable easily.


When using PTFE-Glass - especially in big size projects - the cable can be placed beyond the edge of the membrane. In this case the outer boundary of the membrane panel is edged with a keder line, fixed with a pair of clamping bars. Metal strips fixed on these clamping bars embrace the cable to establish a connection between cable and membrane.


Instead of boundary cables it might be sufficient to use a belt only. This is an option for small size membrane structures. In this case the belt is wraped into the membrane and then stiched to form the edge.


Rigid edges are directly connected to the primary construction by fixing devices such as clamping profiles or keder profiles. In this case the outer boundaries of membrane panels are edged by a keder. This allows to enter the membrane into the fixing devices and prevents slipping out of it.


The keder line is a rope out of Polyester or EPDM rubber (ethylene propylene diene monomer (M-class) rubber),  an elastomer. The keder line is fabricated by wrapping the membrane boundary around the keder and then welding the two membrane panels on each other. The keder allows the fixation of membrane panels as the keder prevents the membrane from being pulled out of the profile.


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