Chapter 2.7 Tension and Suspension Structures

This chapter investigates the properties and use of tensile fabric and suspension structures in buildings with initial references to bridges which are more commonly associated with this form of structure. The starting principle of catenary action and resolution of a suspension bridge cable forces is followed the example of a real stadium roof at Chelsea Football Club. A cable stay bridging structure at Lancaster University is reviewed together with a suspended walkway in Manchester, UK. The chapter concludes with an examination of simplified methods of analysis of tensile roof structures.

Figure 2.7.8 Chelsea South Stand Roof
Figure 2.7.8 shows an overhead view of the South Stand roof in which the overhead roof beams hang from a catenary (in this case steel tubes with flange joints). The catenary is anchored at the ends by trusses which restrain horizontal end reactions so that they are self-contained. The vertical forces are carried to ground by columns to the perimeter of the stand. Hanging structures are a way of creating slender supports which do not have to extend to the ground floor.
Calculation of approximate Tie Force
Area of Floor carried by bar per floor:

1/2 floor width x distance between bars 1.5m²

Weight of floor carried (Self Weight and Live load is 5kN/m²):

Area carried x Unit Load = 5×1.5 = 7.5kN Total load carried by bottom bar over 6 stories:

6 x 7.5 kN = 45kN

Figure 2.7.16 Goodwood PVC Tension Roof
The beauty of approximate design of tension structures is that the stretched internal load is used; non-linearity is not a concern. A constant fabric stress is assumed and the loading resolved locally thereof.