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Portal Frame Design

Portal Frame Design. Introduction. Portal frames are designed to carry lightweight roof coverings. They often constructed of steel, aluminium, concrete, timber or composite material.

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Portal Frame Design

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  1. Portal Frame Design

  2. Introduction • Portal frames are designed to carry lightweight roof coverings. • They often constructed of steel, aluminium, concrete, timber or composite material. • They are commonly used for single or multi-span buildings with flat, pitched, arch north light and monitor roofs. • Three basic forms of portal frames are Rigid portal frame; Two-pin portal frames and Three-pin portal frames.

  3. Introduction Refer to notes to: http://en-gb.facebook.com/note.php?note_id=298379392385

  4. Types of Portal Frame • Fixed or Rigid Portal Frame- All connections are rigid giving bending moments of lower magnitude more evenly distributed than other forms. Generally used in smaller portals where moments transferred to foundations are not excessive. • Two Pin Portal Frame- Frame hinges are used at base connections to eliminate tendency of base rotating. The bending moment resisted by the members is greater than in a rigid frame • Three Pin Portal Frame- Hinged joints at base and at centre. Effect of 3rd hinge to reduce bending moment in the spanning members but to increase deflection

  5. Benefit of Portal Frame • Can economically enclose a large area • Floor areas unrestricted by long runs of walls, more flexible in use • Good floor to ceiling heights • Frame quicker to build than walls saving time and money

  6. Factors influence wind loading • Geographical location – Malaysia, London, KL, Perlis, etc… • Physical location – city, small town,etc… • Topography – hill, valley, slope area, etc.. • Altitude – height above mean sea level • Building shape – square, rectangular, irregular, etc… • Roof pitch – shallow, steep, mono-pitch, multi-bay, etc.. • Building dimensions • Wind speed and direction • Wind peak factor Refer to CP3: Chapter V: Part 2: 1972

  7. Loading case for frame Consider 3 case for frame: Max Load = 1.4 Gk + 1.6 Qk Min Load = 1.0 Gk • Case 1: Max, max, Max • Case 2: Max, min, Max • Case 3: Min, max, Min

  8. Portal frame analysis and design • Analysed either by assuming linear elastic behavior or by basing the analysis on the basic principles of plastic theory. • Plastic desinged frames are lighter than elastically designed frames, however higher stability bracing and check will needed,

  9. Example calculation: Example 17-1 (handout)

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