The main framing of PEB systems is analyzed by the stiffness matrix method. The design is based on allowable stress design (ASD) as per the American institute of Steel Construction specification or the IS 800.The design program provides an economic and efficient design of the main frames and allows the user to utilize the program in different modes to produce the frame design geometry, loading and the desired load combinations as specified by the building code opted by the user. The program operates through the maximum number of cycles specified to arrive at an acceptable design. The program uses the stiffness matrix method to arrive at an acceptable design. The program uses the stiffness matrix method to arrive at the solution of displacements and forces. The strain energy method is adopted to calculate the fixed end moments, stiffness and carry over factors. Numerical integration is used.
The design cycle consists of the following steps:
Frame design can handle different types of loadings as described below:
Following are the main design codes generally used:
AISC: American institute of steel construction manual
AISI: American iron and steel institute specifications
MBMA: Metal building manufacturer’s code
ANS: American national standards institute specifications
ASCE: American society of civil engineers
UBC: Uniform building code
IS: Indian standards
DESIGN METHOD : Allowable stress design method is used as per the AISC specifications.
DEFLECTIONS : Unless otherwise specified, the deflections will go to MBMA, AISC criteria and standard industry practices.
PRIMARY FRAMING : Moment resisting frames with pinned or fixed bases.
SECONDARY FRAMING : Cold formed Z sections or C sections for purlins or girts designed as continuous beams spanning over rafters and columns with laps.
LONGITUDANAL STABILITY : Wind load on building end walls is transferred through roof purlins to braced bays and carried to the foundations through diagonal bracing.
DESIGN SOFTWARE : The latest software that is used for design is STAAD 2007.
DESIGN PROCESS : The frame data is assembled based on number of frame members, number of joints, number of degrees of freedom, the conditions of restraint and the elastic properties of the members. Based on this, the data is stored and member section properties are computed. The overall joint stiffness matrix is obtained based on the above frame data by summation of individual stiffness matrices considering all possible displacements. The load vector is then generated based on the loading data and the unknown displacements are obtained by inverting the overall joint stiffness matrix and multiplying with the load vector.