Dynamic responsive characteristics of nailed plywood–timber joints under harmonic vibrations

摘要

Dynamic tests of nailed plywood–timber joints are conducted under harmonic vibrations from 2 to 7 Hz. The principal results are as follows: under dynamic loading, nailed plywood–timber joints may break in low-cyclic bending fatigue failure of nails besides the other failure modes typical under static loading. The dynamic response of nailed plywood–timber joints is clearly dependent upon both the input frequency and the acceleration. These responsive characteristics arise from the nonlinear load–slip relationships and the characteristic cyclic stiffness degradation of nailed joints; that is, the cyclic degradation of the equivalent linear stiffness decreases the resonant frequencies of the same joints, which results in a transition of dynamic responses. It indicates that frequency components of seismic waves resonant to the frequencies corresponding to safety-limit stiffness of nailed joints may lead them to critical failures, even if the accelerations do not exceed the accelerations equivalent to the static damage-limit resistance.