LSAA MADA Workshop Extra Resources

Transcription

1 LSAA MADA Workshop Extra Resources Cables, fittings, shade, wind effects on shadecloth structures and other bits and pieces Structural Cable Basics Having established the application, load requirements and desired level of corrosion protection, consideration should be given to: 1. Cable Construction. 2. Cable Termination Methods. 3. End Fitting Options. 4. Connections, Clamps, anchors and associated fittings. 1. Cable Construction Options 7 X 1 9 w i r e r o p e 7 X 7 w i r e r o p e 1 X 1 9 s t r a n d 1 X 31 s t r a n d VVS 3 F u l l l o c k e d c a b l e and Shadecloth Issues 1

2 2. Cable Termination Methods Swaged Ferrule eye Wire rope grips Swaged terminal end Socket End. 3. End Fitting Options Swaged end terminations Compact Adjusters (Turnbuckles) Swaged end terminations Turnbuckles (Full Adjustment) Swaged end terminations Threaded Ends and Shadecloth Issues 2

3 Stainless Cables Swaged End Terminations Inclined pin ended columns are more efficient and aesthetically pleasing when they bisect the two tensile loads. Things that go wrong not designed properly! Reaction loads grossly underestimated probably NO engineering calcs done by contractors Cantilevered columns need a solid footing not just a bag or two of concrete!! Shadecloth structures need prestressing. They MOVE A LOT under mild winds. Playground structures need CLEARANCE to fabric especially shadecloth panels and Shadecloth Issues 3

4 7 8 and Shadecloth Issues 4

5 9 10 and Shadecloth Issues 5

6 11 12 and Shadecloth Issues 6

7 13 Behaviour under moderate wind and Shadecloth Issues 7

8 Behaviour under moderate wind Behaviour under moderate wind and Shadecloth Issues 8

9 Behaviour under moderate wind A sample playground North and Shadecloth Issues 9

10 A glance at wind effects on shadecloth structures Often wave like movements in larger flatter panels that are prestressed Very large displacements in loose panels measured in metres An approach to wind loads on shade cloth panels and Shadecloth Issues 10

11 Example structure where edge cables not adjusted correctly mild wind. Note position of shade on ground (mid afternoon, winter) Avoid extremely pointy corners, and triangles and keep ratios of panel side lengths within 25% if possible for 4-sided panels. Note sagging of cloth and large areas of wrinkles as well as the position of the shade on the ground. and Shadecloth Issues 11

12 Shade panel removed during winter? Attachment cleat had only one small hole? Now a slide for the fabricators... (and engineers) Discuss force transfers given that under wind most loads are taken by the windward edge. and Shadecloth Issues 12

13 25 26 and Shadecloth Issues 13

14 So you are providing SHADE?? Skin cancer now taken very seriously Schools, playgrounds need EFFECTIVE SHADE between 10am 2pm at least Separate panels have very large gaps between Overlapping panels, or panels joined together at mid sides may help. It is not the area directly under a membrane that is shaded sometimes NONE of the area under is shaded. Playground, open carparks are examples where there is inadequate shading not good for a designer s reputation, or the industry!! Using approx 10% sag, about 220mm corner attachments, 200 dia post 65% cover!!! and Shadecloth Issues 14

15 Earth shown with sun angles at extreme seasons. A shade panel at height h above ground at Sydney (lat 34 deg South) with extreme sun angles as 1, 2 Does not show effects of sun angles early morning or late afternoon. Software may simulate shade. USE A TORCH ON A PHYSICAL MODEL Suppliers of shade structures should supply Shade Diagrams to clients and Shadecloth Issues 15

16 31 32 and Shadecloth Issues 16