What design philosophy states that maximum stress in a member must be below an allowable stress under service conditions and is also known as the Working Stress Design?

• A. Load Factor Design
• B. Allowable Stress Design
• C. Load and Resistance Factor Design
• D. Level I Earthquake Motions

Answer: (B)

Allowable Stress Design, also called Working Stress Design, is the approach that requires the maximum stress in a member under service loads to stay below an assigned allowable stress. The allowable stress comes from the material’s strength divided by a safety factor, reflecting uncertainties in loads, material properties, and construction. If the service-induced stress remains below this limit, the member is considered safe for normal use. This contrasts with more modern reliability-based methods that use factored loads and resistances to guarantee performance under worst-case or extreme conditions. The other options describe different design philosophies or seismic input categories, not the simple service-stress limit used in ASD/WSD.