Exploratory study on fatigue behaviour of laterally loaded, nailed timber joints, based on a dissipated energy criterion

Abstract

Exploration of damage accumulation and reliable prediction of the fatigue lives of laterally loaded, nailed timber joints, are important to proper engineering design of wood structural systems subjected to earthquakes, cyclones/hurricanes or other loads causing fl uctuating force fl ows in such joints. Failure of nailed timber joints typically involves the combination of yielding at plastic hinges in nail and/or the crushing of wood under nails. Force-based criteria can predict the static strength of such joints but cannot reliably predict fatigue behaviour because that depends on loading history and the dissipation of energy within plastic nail hinges and/or crushed wood. In this study, the failure modes, damage accumulation and fatigue life of nailed timber joints subjected to reversed cyclic loads under load-control condition were studied. The results showed that there are two failure modes of nailed timber joints, i.e., ductile failure of nails when the applied load level was higher than 85 % of the static maximum load to failure ( P max ) and brittle failure when the applied load level was < 85 % of P max . The damage accumulation involved three phases, i.e., damage initiation, damage propagation and failure. Fatigue life of nailed joints under reversed cyclic loads was modelled by an energy criterion that separated dissipated energy into non-damaging and damaging components demarcated by the fatigue limit. This approach replicated the behaviour of nailed joints tested at 20 load levels of fully reversed repetitive cyclic loading.

Static and dynamic tensile shear test of glued lap wooden joint with four different types of adhesives

“…Wooden joints loaded under a quasi-static loading were studied by Hass et al (2014). Studies on wooden joints under fatigue loading were performed only at a certain stress level (Olson et al 1955;Li et al 2012). The present study explores the relation between the short-term static and long-term fatigue failure at several stress levels of glued wooden joints.…”

Estimation of failure lifetime in plywood-to-timber joints with nails and screws under cyclic loading

“…They found that a fatigue life of laterally loaded nailed joints subjected to cyclic displacement or loads depends on the fatigue properties of nails and the fatigue life of joints, estimated from the fatigue data for nails in combination with Johansen's yield theory for joints with slender fasteners. Gong et al [11] and Li et al [12] explored and estimated the fatigue life of nailed joints in terms of damage-dissipated energy by a modified empirical energy-based criterion. They stated that the fatigue life of nailed joints could be more accurately estimated using an energy-based criterion.…”

Fatigue behavior of Japanese cypress (Chamaecyparis obtusa) under repeated compression loading tests perpendicular to the grain

“…An improvement of bending fatigue characteristics was suggested based on the observation of failure modes. In terms of wooden joints, Li et al (2012) conducted a shear fatigue test on nailed joints and reported on the change in the shear performance. These authors developed a prediction for the fatigue life of the joint sections based on energetics observations.…”