Numerical Simulation and Variability Analysis of Mechanical Behavior of Braced Glulam Frames

AbstractThis paper summarizes the results of a numerical simulation and subsequent variability analysis of the lateral load-resisting behavior of unbraced and chevron-braced glulam portal frames. Longitudinal tension/compression strengths of each glulam member were determined based on wood-size effect theory. The finite-element method (FEM) and an experimental study were carried out to determine the nonlinear mechanical behavior of glulam braces and bolted glulam beam-to-column connections. OpenSees “Pinching4” hysteresis models were adopted to model the mechanical behavior of both glulam braces and bolted beam-to-column connections. An FEM model of the glulam frames was developed to predict the lateral load-resisting hysteretic response of such frames. The stochastic finite-element method was used to calculate the frame capacity considering random distributions of connection and brace capacity. The FEM model presented can represent the nonlinear and hysteretic pinching behavior of an unbraced glulam frame whose behavior is dominated by splitting in the connection regions. Similarly, the strength softening and stiffness degradation of a chevron-braced glulam frame was also captured. Response surface method analysis was used to regress braced frame capacity from 200 analyses to a single set of capacity variables. The approach described in this paper demonstrates promise for optimizing the industrial-scale production of glulam portal frame structures.