Structural Design Philosophies ASD & LRFD

Structural engineering design philosophy is based on determining the demand on an element and designing that element with the capacity to withstand that demand. There are two basic approaches to developing the demand; LRFD (Load Resistance Factored Design) and ASD (Allowable Stress Design). Historically, design of different materials (wood, steel, concrete and masonry) has used either ASD or LRFD. This interactive, online course will look at the origins of the two approaches, discuss traditional uses of ASD and LRFD and their safety implications. We will also investigate the differing load combinations as defined in the International Building Code®. Understanding these approaches is an essential element of a life safe design process.

• Explain the background of ASD and LRFD
• Compare the numerical demands forces developed by the two approaches in terms of a single material and the resultant effects on capacity (including load combinations required for a safe design)
• Compare and contrast the traditional uses of ASD and LRFD for different materials
• Define the change from allowable stress design to allowable strength design, as defined by AISC (Steel)
• Discuss the implications of choosing between the two systems when beginning a new design or a renovation project in terms of safety, cost and constructability