Analysis of wood‐composite laminated frames under dynamic loads—analytical models and model validation. Part I: connection model

Abstract

This paper describes the analytical models of timber connections that were used to simulate the full time‐history response of moment‐resisting frames subjected to dynamic loads. Special attention was paid to connection modeling to capture the hysteretic damping that significantly affected the performance of the system subjected to dynamic forces. To model the hysteretic properties of the dowel‐type connections a combination of bilinear springs and gaps was used. This approach allows the modeling of various hysteretic shapes including pinching, asymmetric behavior, contact phenomena, and an initial slip of the fasteners. Load–deformation curves obtained from the cyclic experiments of small‐ and full‐scale joints were used to extract the model parameters. The hysteretic models were verified by comparing the simulation with the experimental data obtained from cyclic tests. The comparison reveals that the presented approach can be successfully used to simulate the load‐history‐dependent behavior of timber joints, provided that strength degradation is negligible and a brittle failure does not occur. The predictive ability of a 3D frame model will be demonstrated in Part II by comparing the simulation with the results of shake table experiments.

Shake table tests of small- and full-scale laminated timber frames with moment connections

“…The connections were loaded into inelastic regions accompanied by stiffness and strength degradation. (Heiduschke et al 2004) As discussed in Heiduschke et al (2006a, b), most of the energy dissipation occurred through frictional effects between beams and column at small joint rotations (less than 0.02 rad) while the plastic deformation of wood and steel fasteners were responsible for energy dissipation at larger joint rotations.…”

“…The goal of the small-scale shake table tests was to understand the seismic behaviour of statically indetermined timber frames when loaded into inelastic regions. While it is unlikely to predict the nonlinear behaviour of full-scale systems, the small-scale tests were useful to study the frame response in regard to the amplification of acceleration response, angular rotations in the joints, failure modes and system damping as well as to validate numerical models (Heiduschke et al 2006a, b). Figure 2 shows the definition of the symbols and a 3D view of a full-scale frame mounted on the shake table.…”

“…This is important from the viewpoint of analytical modelling, since identical constitutive laws can be applied to both connections. The development of numerical models that capable of simulating full timehistory response of timber frames was discussed by Heiduschke et al (2006a, b). Shake table 290 Fig.…”

A component approach for the hysteretic behaviour of connections in cross‐laminated wooden structures

“…The model was used to predict the shear wall monotonic response in some experimental tests. Finally, Heiduschke et al [27] developed a model that represent the semirigid connections, modelled as an assemblage of springs and dampers, in a moment-resisting wood frame, obtaining a good accuracy also in the estimation of the dissipated energy. Falk et al [23] developed a 2-D element for monotonic analysis of wood diaphragms, whereas Yasumura [24] and Collins et al [25] focused on the dynamic analysis of light wood frame structures.…”

Analysis of wood‐composite laminated frames under dynamic loads ‐ analytical models and model validation. Part II: frame model

“…The experiments showed that the frames responded nonlinearly to the dynamic loads and that most of the energy dissipated in the beam‐to‐column (BC) and column‐to‐foundation (CF) connections while members deformed elastically. The viscous damping that is associated with wood material is low, and most of the damping in the system is a hysteretic damping resulting from friction, plastic deformation of wood, and plastic hinges in steel connectors – see Part I F 4. The amount of system damping depends on the magnitude of the deformations, thus resulting in a nonlinear system requiring a full nonlinear time‐history analysis.…”