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Comprehensive Guide to Portal Frame Design Principles

Learn about the types, benefits, factors influencing wind loading, and analysis methods for portal frames. Explore the design options for different structures and find useful calculations and case studies.

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Comprehensive Guide to Portal Frame Design Principles

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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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