Postelastic Behavior of Single- and Double-Bolt Timber Connections

A nonlinear numerical model is developed to study the behavior of single- and double-bolted timber connections with relatively low member thickness-to-fastener diameter ratios. These structural joints tend to fail in a brittle fashion. Nonlinear geometry due to increased sliding contact between the bolt and the hole is modeled using the Lagrange multiplier algorithm. A plasticity-based constitutive compressive material model is developed to predict the nonlinear wood behavior in the contact zone(s). Numerical simulations of postelastic deformations of one- and two-bolt connections are compared to experimental results from tensile tests undertaken on double shear steel to glued-laminated-timber to steel connections. The established model is capable of tracing the inelastic deformations locally and globally and predicting unequal load fractions that are transferred by each bolt in two-bolt connections. Connection capacities estimated with the new elastoplastic model are bounded by classical elastic and fully plastic model predictions. Implementation of the new model is via finite element approximation representations.