Study on interaction of Viscoelastic and Mechano-sorptive creep and effect of Fibre Reinforcement on creep of Timber beams

Abstract

Timber is a sustainable material widely used in structural elements. Its viscoelastic nature, in which the stress-strain relation varies with time, poses significant challenge to the durability of timber structures. Creep of timber under constant loading depends on various factors like stress level, moisture content, load-to-grain angle, temperature, relative humidity etc. Among these, relative humidity and moisture content in timber are the most crucial. Drastically varying moisture content causes mechano-sorptive creep. However, the interaction and contribution of various factors causing creep is still a matter of research. Various codes provide generalized creep coefficient for long term deflection and load reduction factors. A detailed rheological model was proposed by Toratti which addresses mechano-sorptive creep explicitly, incorporating both recoverable and irrecoverable part in creep. This paper aims to review the study on interaction between viscoelastic creep and Mechano-sorptive creep in various environmental conditions. Effect of reinforcing timber beams, on the long term deflection due to creep is also made a subject of study to identify a possible solution to the accelerated deflection by Mechano-sorptive creep, which will be unavoidable in tropical areas with extreme climactic changes. A comparative study between the various standard codes with Indian Standard Codes for timber with respect to creep, is also made, to identify the gaps in IS codes.