Reliability Analysis Of Timber Structures And Method For Determining The Strength Design Value Of Wood Products

Design values of importing dimension lumber and visually stress-grade glued laminated timber and mechanical modulus-graded glued laminated timber in the Chinese timber structures design code were based on the soft conversion method. In this paper, by calculating the reliability of the design values of importing dimension lumber and glued laminated timber, the conclusion that the design values of modern structural wood products based on the soft conversion method did not meet the requirement of Unified standard for reliability design of building structures was obtained.Given the wide range of the coefficient of variation of strength between various modern structural wood products, the performance function of wood members was developed and the reliability analysis of the members in bending, compression or tension conducted. The relationship curves between the partial safety factor and the coefficient of variation were obtai ned. Following the principle of being safe and reliable, also of being reasonable and economical, it was proposed that the relationship curve under the combination of residential floor load and dead load with a live to dead load ratio ρ of 1.0 be the reference curve for determining the design strength value. Safety modification measures for other load combinations and load ratios were also proposed.Suggestions for determining the design values of glued laminated timber and importing dimension lumber made by widely used species were given, which could meet the reliability requirement of Unified standard for reliability design of building structures.The relationship between the partial safety factors with respect to the safety class of timber structures was investigated, thus providing the reference for choosing the suitable wood product or for determining the value of the importance factor. Meanwhile, suggestions for determining the design value of the shear strength, compression and tension strength perpendicular to grain were given.By using statistics method, the characteristic values of domestic dimension lumber of northeast larch was proposed. Suggestions of the design values of northeast larch dimension lumber was also proposed.