Timber member resistance to snow and wind loads in Polish mountain zones

The resistance of timber members in structures decreases over time. It depends on the type of load – permanent or variable- and the sort of timber. Strength reduction effects, often referred to as creep-rupture effects, due to long- term loading at high stress ratio levels, are well known for many materials such as aluminum and concrete. Wood materials are greatly affected by a reduction in strength with the duration of permanent and variable loads. The methods for calculating these reductions and the data relevant for structural timber resistance are presented. Based on snow and wind measurements over 45 years from mountain zones in Poland (Zakopane, Świeradów, and Lesko), the reduction factors- kmod for wood members, according to PN-EN – 1995, were estimated.