LSAA Membrane Structures Resource 8/26/2016 Introduction to Membrane Structures Introduction to Membrane Structures An Introduction to Introduction & Brief History of Tension Fabric Structures Tensile Structures LSAA Presentations Peter Kneen, Bob Cahill, Peter Lim LSAA‐MADA Workshop Resource 2016 Introduction to Membrane Structures Introduction to Membrane Structures Introduction The Birth of the MSAA 1981 / LSAA • “Tension Fabric Structures” Presentations by the LSAA • About the Lightweight Structures Association • Main Topics to be covered • History & Fundamentals • Textile materials • Structural supports • Design principles and procedures • Fabrication, assembly and erection procedures LSAA 2016 Workshop LSAA 2016 Workshop MADA 3 MADA 4 Resource Material Resource Material LSAA ‐ MADA Membrane Structures Workshop 2016 1 LSAA Membrane Structures Resource 8/26/2016 Introduction to Membrane Structures Introduction to Membrane Structures LSAA 2016 Workshop LSAA 2016 Workshop MADA 5 MADA 6 Resource Material Resource Material Introduction to Membrane Structures Introduction to Membrane Structures Lightweight Structures Association of Australasia About the LSAA • Founded as the MSAA in 1981 when membrane structures were being established in Australia / NZ • The aim of LSAA is to promote proper design and • Members: Engineers, Architects, Fabricators, Contractors, Suppliers, application of lightweight structures including: Students • Tension Fabric Structures – “solid” and “open” fabrics. • Holds Conferences and Symposiums • Cablenet and cable supported structures. • Shell and folded structures, Space grids. • Holds LSAA Design Awards every 2 years • High Tech Glazing systems. • NFP organization run by elected committee supported by a part time EO. • New forms of large span, energy efficient or sustainable construction • Website: www.LSAA.org LSAA 2016 Workshop LSAA 2016 Workshop MADA 7 MADA 8 Resource Material Resource Material LSAA ‐ MADA Membrane Structures Workshop 2016 2 LSAA Membrane Structures Resource 8/26/2016 Introduction to Membrane Structures Introduction to Membrane Structures Development of Modern Fabric Structures Some early Australian structures • Pioneered by Frei Otto in 1950s, 1978 Dean Park Townsville eg, Dance Pavilion in Cologne (1957) “New” concepts and unknowns LSAA 2016 Workshop LSAA 2016 Workshop MADA 9 MADA 10 Resource Material Resource Material Introduction to Membrane Structures Introduction to Membrane Structures Air Supported Used for many outdoor pools for a while in the 1980s Burswood (Perth) only cable restrained air dome in Australia LSAA 2016 Workshop LSAA 2016 Workshop MADA 11 MADA 12 Resource Material Resource Material LSAA ‐ MADA Membrane Structures Workshop 2016 3 LSAA Membrane Structures Resource 8/26/2016 Introduction to Membrane Structures Introduction to Membrane Structures Expo 1988 Brisbane Bicentennial Exhibition 1988 LSAA 2016 Workshop LSAA 2016 Workshop MADA 13 MADA 14 Resource Material Resource Material Introduction to Membrane Structures Introduction to Membrane Structures Superspan Shadecloth Structures – Early 1980s Prototype 1982 4x2 Panels (14.3m square) With / without wall panels Observed under winds for 4 months Uplift forces and deflections recorded. 70% shade factor, knitted, webbings Knitted, not woven, seat belt webbing, 14.3 m square panels joined. LSAA 2016 Workshop - Many successful structures BUT some major failures. Industry has not learnt LSAA 2016 Workshop MADA 15 MADA 16 Resource Material Resource Material LSAA ‐ MADA Membrane Structures Workshop 2016 4 LSAA Membrane Structures Resource 8/26/2016 Introduction to Membrane Structures Introduction to Membrane Structures Green Scene ‐ Victoria Car Storage Yards Insert text box LSAA 2016 Workshop LSAA 2016 Workshop MADA 17 MADA 18 Resource Material Resource Material Introduction to Membrane Structures Introduction to Membrane Structures Part of the current interest. Insert text box Insert text box LSAA 2016 Workshop LSAA 2016 Workshop MADA 19 MADA 20 Resource Material Resource Material LSAA ‐ MADA Membrane Structures Workshop 2016 5 LSAA Membrane Structures Resource 8/26/2016 Introduction to Membrane Structures Introduction to Membrane Structures Structural Elements & Actions Some Traditional Structures • Cables, ropes, rods – tension (efficient) • Roofs – loads applied to metal decking to purlins to • Columns, struts – compression (OK but buckling) trusses or portal frames and down to foundations. Mainly by bending. • Beams – bending (inefficient) • Slabs – bending (inefficient) • Floors – loads applied to slabs hence by bending / • Walls – compression, shear shear to isolated edges beans and then to columns. • Trusses – “efficient beams” but costly to make [or floor boards to joists to bearers to main beams to piers etc] LSAA 2016 Workshop LSAA 2016 Workshop MADA 21 MADA 22 Resource Material Resource Material Introduction to Membrane Structures Introduction to Membrane Structures Examples of Efficient Structures What is a Tension Membrane Structure? • Resists applied loads by tensile actions –and hence • When the traditional methods become too makes an optimum use of material expensive and there is some architectural freedom in terms of geometry • Needs a level of pretension for geometric stability • Arches, Suspension cables, Domes, shells • Often doubly curved in space (saddles and cones) • Tension Fabric Structures are efficient for increasing spans with proper engineering design and understanding the materials LSAA 2016 Workshop LSAA 2016 Workshop MADA 23 MADA 24 Resource Material Resource Material LSAA ‐ MADA Membrane Structures Workshop 2016 6 LSAA Membrane Structures Resource 8/26/2016 Introduction to Membrane Structures Introduction to Membrane Structures Fundamental Concepts The Membrane • Membrane structures must be kept taut and free of wrinkles • Multi‐tasking element • Environmental barrier • This is achieved by prestressing the membrane surface • Filters UV, controls lighting, water barrier, thermal properties • Making it smaller than the final size • Flexible, prestressed, self supporting • Design the shape to be “saddle shaped” • Main loads are from prestress and wind (Australia) • Design the support system to define the form • Being able to determine cutting patterns well • Typically are attached to more traditional support elements – cables, beams, masts, arches & rings • Having a good feel for loads and detailing • Having the ability to make adjustments LSAA 2016 Workshop LSAA 2016 Workshop MADA 25 MADA 26 Resource Material Resource Material Introduction to Membrane Structures Introduction to Membrane Structures Inter related aspects of membrane structures. Saddle shaped surfaces • Geometry • Required / very desirable for all but “air supported” • Aim for a “saddle shaped” surface structures. • Traditional support elements have a geometry to achieve this anticlastic surface shape • External Loads • Wind pressures – downwards & uplift, influenced by geometry • Internal fabric stresses • Coupled with the saddle shape combine to resist external loads LSAA 2016 Workshop LSAA 2016 Workshop MADA 27 MADA 28 Resource Material Resource Material LSAA ‐ MADA Membrane Structures Workshop 2016 7 LSAA Membrane Structures Resource 8/26/2016 Introduction to Membrane Structures Introduction to Membrane Structures Note: a flat surface has 360 deg sum. The difference between 360 and the actual sum of included angles (for example 360‐240=120 deg) can be used as a measure of curvature (and perhaps aesthetics or impact) Multiple simple modules of the same panel can be used for an improved overall impact. LSAA 2016 Workshop LSAA 2016 Workshop MADA 29 MADA 30 Resource Material Resource Material Introduction to Membrane Structures Introduction to Membrane Structures A look at a PVC cone structure Typical Cone Structure • Components (fabric, cables, columns, bale ring) • Fabric prestress (want fabric to remain taut) • Forces generated (in cables, columns etc) Top of cone clamped • Resisting the forces (different means) to a circular bale ring • Engineering – Peter Lim • Basic geometry aspects • Formfinding, structural analysis Fabric stress Edge cable • Patterning span & sag determine cable tension LSAA 2016 Workshop LSAA 2016 Workshop MADA 31 MADA 32 Resource Material Resource Material LSAA ‐ MADA Membrane Structures Workshop 2016 8 LSAA Membrane Structures Resource 8/26/2016 Introduction to Membrane Structures Introduction to Membrane Structures Reg 90 kg Garry 110 kg Terry 85 kg Joan 70 kg Lyn 75 kg Total = 430 kgs = 4.3 kN approx. A little bit of maths gives us an idea of Spread over 4 – cable forces and 4.5 metres hence support reactions. = say 1 kN/m (“prestress only”) FabricLSAA 2016 Workshop prestress (small PVC cone) say 1 kN/m to 2 kN/m LSAA 2016 Workshop MADA 33 MADA 34 Resource Material Resource Material Introduction to Membrane Structures Introduction to Membrane Structures Typical small bale ring – 4 segments, 4 lifting points How do we resolve some of the loads generated? Fabric stresses will cause bending and torsion in the bale ring LSAA 2016 Workshop LSAA 2016 Workshop MADA 35 MADA 36 Resource Material Resource Material LSAA ‐ MADA Membrane Structures Workshop 2016 9 LSAA Membrane Structures Resource 8/26/2016 Introduction to Membrane Structures Introduction to Membrane Structures LSAA 2016 Workshop LSAA 2016 Workshop MADA 37 MADA 38 Resource Material Resource Material Introduction to Membrane Structures Introduction to Membrane Structures This bale ring is suspended from above the structure This