Session 6.2 - Structural Timber

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Full Sized House Cyclic Racking Test

S.J. Thurston and A.B. King

Earthquake and wind loads for timber framed house designs in New Zealand are specified in NZS 3604. Various lining and cladding manufacturers publish bracing strengths for their wall systems based on the BRANZ P21 racking test. The P21 tests are carried out on a short length of wall with contrived end restraints to simulate continuity of actual construction.

To verify that this design approach is realistic, an existing house was relined and cyclically racked to failure. This paper compares the actual house strength with the strength determined using the NZS 3604 design provisions.

Paper 029: [Read][Print]

Keywords: house racking seismic test

The Effect of Eccentric Overturning Restraint in Complete Shear Wall Assemblies

S.E. Pryor

In this paper various aspects of the effect of eccentricity in overturning restraint devices used in light-framed wood shear walls is discussed. To accurately assess the demand on the tension end post, three dimensional nonlinear finite element modeling is used to investigate the effect that sheathing/nailing can have on the boundary posts in shear walls. Results are presented at both the allowable stress design level and at the strength limit state, and these results are compared against a bare post analysis. Additionally, both one and two story conditions are analyzed. The results show that the sheathing/nailing can significantly reduce the internal post stresses, and that this reduction is proportional to post stiffness and nail spacing.

Paper 159: [Read][Print]

Keywords: holdown, eccentricity, overturning, sheathing, nailing

Earthquake Duration Effects on Very Low Cycle Structural Damage Estimates

J.W. van de Lindt and G. Goh

The duration of strong ground motion has been shown to have a significant effect on the level of damage sustained by engineered structures during moderate to severe earthquakes. In this study, the authors develop and make use of the regressive relationship between the fundamental structural period of a system and the number of deformation response cycles during an earthquake of a specified duration. Damage is assumed to accumulate linearly in a structure or component based on the well-known Park-Ang damage model. The deformation response peaks for non-linear systems can be shown to closely fit a two-parameter Weibull distribution. Knowledge of the statistics of the response peaks for non-linear systems was combined with the theory of order statistics to quantify the effect of duration on damage estimates. It is concluded, based on the mean structural reliability indices for a suite of non-linear systems, that earthquake duration has a significant effect that it should be considered in seismic reliability analyses that focus on low-cycle damage.

Paper 009: [Read][Print]

Keywords: earthquake duration, damage index, structural reliability index

Comparison of Pseudo-dynamic Test and Inelastic Time History Computer Analysis

S.J. Thurston

The paper discusses the reasoning behind the performance of pseudo-dynamic tests, the background and the theory. The pseudo-dynamic testing facilities developed at BRANZ were verified by comparing with inelastic time history analysis.

Paper 030: [Read][Print]

Keywords: Pseudo-dynamic PD test walls

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