Glossary: Modulus of Elasticity
A material property measurement (normally in psi or GPa) representing stiffness or structural resistance to elastic deformation under load.
Modulus of Elasticity (E) in Timber Engineering
Modulus of Elasticity, denoted as E, is a primary input in calculating allowable horizontal spans for joists and rafters. Higher E ratings indicate stiffer timber species that sag less under loads:
- Wood Species Variation: Structural Douglas Fir carries a typical Modulus of Elasticity around 1,600,000 to 1,900,000 psi, while Southern Yellow Pine ranges from 1,400,000 to 1,800,000 psi depending on grade.
- Deflection Resistance: timber design codes use E along with the structural moment of inertia (I) to calculate deflection under uniform design live loads.