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Pitched Roof Frames
Plastic analysis of pitched roof frames is performed using the semi-graphical method [Heyman,Baker] based on the following assumptions:
For the combination of factored dead, live and wind loads three possible mechanisms are invesigated:
For each of the mechanisms, output gives the over-capacity factor, the reactions at base and the moments at ridge and eaves.
Base reactions are used for designing foundations. Note that the base reactions are factored.
Moments at ridge and eaves are used for designing connections and may turn out to be somewhat higher than the plastic moment capacities of members.
Over-capacity factor is ratio of loads that can be sustained and the loads applied on the structure. An over-capacity factor greater than or equal to 1 indicates that the structure can safely carry the applied load combinations for the assumed mechanism.
Plastic analysis gives no indication of the deflection and stability aspects for which separate checks must be made.
© 1999-2009 Rudra Nevatia