Creep of oak dowel: various loading and environmental conditions

For research of timber joints, the crucial role in force distribution inside the joint is played by distribution and variability of stiffness of the dowels. Not only the instant stiffness, but the one that we can encounter after some longer period. Also, this value and its statistical distribution is influenced by many other factors, however, humidity and temperature are in timber (oak) dowels of utmost importance. In the work results of a creep experiment made using a special testing rig is presented. It has been found, that biggest changes in creep behavior are in case if very humid conditions are present, and, also, that cycling the temperature in high humidity conditions can produce about 104% of the original instantaneous displacement. The result is not surprising, however, new insights are made thanks to relatively high number of samples and ability to produce some statistics. Another outcome is relation of dowel stiffness in time to the level of applied stress, which is quantified in the article