Remains the historical standard for wood and is widely used due to its simplicity and the extensive existing library of hardware catalogs based on ASD. Load and Resistance Factor Design (LRFD)
In modern structural engineering, designers of wood systems must navigate two distinct philosophies: and Load and Resistance Factor Design (LRFD) . Both are currently accepted by the National Design Specification® (NDS®) for Wood Construction. 🏗️ Design Philosophies Allowable Stress Design (ASD) Structural wood design: ASD/LRFD
"Factored" loads increase the design burden based on the uncertainty of the load type (e.g., higher factors for live loads vs. dead loads). Remains the historical standard for wood and is
Standard in steel and concrete design and gradually gaining ground in the wood industry. ⚖️ Key Differences for Designers Load Factors Usually 1.0 (unfactored) Multipliers > 1.0 (e.g., 1.2, 1.6) Material Strength Reduced by Factor of Safety Multiplied by resistance factor ( Calculations Stress-based ( Strength-based ( Efficiency Can be conservative for mixed loads More efficient for transient load combinations 🪵 Why Choose One Over the Other? ⚖️ Key Differences for Designers Load Factors Usually 1
Applies separate factors to both loads (Load Factors) and material strength (Resistance Factors).
Applies a single Factor of Safety to the material's ultimate strength to determine "allowable" stresses. Loads: Uses actual expected (unfactored) service loads.