[WEEK 6] 1
Roofing
Small Module Materials Earth à Terracotta Clay à Ceramic Slate Timber à Shingles Steel à Steel Tiles Concrete à Concrete Tiles Spanning Spaces -‐ Stone spanned by a beam or slab or stone corbel (diagram). -‐ Arches only fail by distortion Large Module Materials -‐ Corrugated Iron [Slope Diagram] [<5, <3, <1 elevations sketch] [Water caught sketch] Roof Types Structural Steel Roofs -‐ Flat: Primary and secondary roof beams -‐ Sloping: Roof beams and purlins combined to create a slope -‐ Portal Frames: Rigid joints between beam and column Trussed Roofs -‐ Ability to span long distances -‐ Therefore efficient Flat Roofs: Usually concrete with a weatherproof membrane, sometimes with tiles so it’s walk able. Space Frame: 3D Plate that span long distances in two directions, usually glass is fitted in between gaps. Light Framed Roofs: -‐ Gable roofs uses roof beam and rafters in a triangular shape. Usually made from timber cold-‐formed steel and sometimes heavier steel (UB or PFC) -‐ Hip Roofs a flattened version of bale roofs. Uses timber and cold-‐formed steel Ferrous (Iron) Iron
Metals
-‐ Good compressive strength -‐ Wrought Iron created when heated then hammered -‐ Cast iron created by puring molten iron into moulds. Steel -‐ Iron Alloy (Carbon +Steel) -‐ Stainless Steel created when Chromium is added Non Ferrous (All other metals) Aluminum: -‐ Easily formed -‐ Light -‐ Strong Copper: -‐ Good conductor -‐ Use to clad a building and as electrical cabling Zinc: -‐ Used for Cladding walls and roofs and galvinising Lead: -‐ Not used as much now due to its toxicity Tin: -‐ Not used as much now, occasionally for roofing Titanium: -‐ Cladding material -‐ Expensive -‐ Good corrosive resistance and Strong Alloys (Combinations of non ferrous metals) Bronze: -‐ Combination of copper & tin -‐ Used for bearings, clips electrical connectors and springs Brass: -‐ Combination of Copper + Zinc -‐ Used for fittings, locks, gears and valves -‐ Easy to cast Zincalum: -‐ Zinc + Aluminum -‐ Used to coat steel [Galvanic Series Diagram] Corrosion: 1. Oxygen 2. 2. Potential Electrons 3. Water 4. Metal Roof Members Timber à Rafters
[WEEK 6] 3 Metal (steel) à Purlins Roof Member sketch Plasterboard Sketch –Domestic/commercial Sites Boxhill: -‐ Extension to a domestic building -‐ Mostly timber construction with stud framing -‐ Steel used to strengthen joints -‐ Minimum clearance of 150mm from timber to ground -‐ Pan tile roofing Pharan: -‐ Extension to a duplex plan (sketch) -‐ Brick building on a concrete slab with steel supports -‐ Brick cavity
Columns Critical Vertical Load Determined By: 1. Length 2. End Fitting Type 3. Material 4. Shape (cross-‐section)
[Pin and fixed joint bending diagram] When describing a component: -‐ Size, Finish, Material, Component Eg. 90x45 Softwood Timber Stud OR 90x45 sw timber stud
[Critical Load Equation] -‐ EI = Material strength -‐ kL = Effective Length -‐ As the denominator (effective length) decreases the critical load increases -‐ This means the smaller the effective length, the stronger the column is.