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Images, eqnz.chch.2010

Today (04/09/14) marks the fourth anniversary since the first earthquake rocked the city and greater Christchurch area. That first quake was magnitude 7.1, and luckily there was only one fatality (possible a heart attack). Since then we have had over 14,000 quakes, most very small in magnitude, but well over 500 of magnitude 4 or greater. 5...

Research papers, University of Canterbury Library

Post-tensioned timber technology was originally developed and researched at the University of Canterbury (UC) in New Zealand in 2005. It can provide a low-damage seismic design solution for multi-storey mass timber buildings. Since mass timber products, such as cross-laminated timber (CLT), have high in-plane stiffness, a post-tensioned timber shear wall will deform mainly in a rocking mechanism. The moment capacity of the wall at the base is commonly determined using the elastic form of the Modified Monolithic Beam Analogy (MMBA). In the calculation of the moment capacity at the wall base, it is critical to accurately predict the location of the neutral axis and the timber compressive stress distribution. Three 2/3 scale 8.6m tall post-tensioned CLT walls were experimentally tested under quasi-static cyclic loading – both uni-directional and bi-directional- in this study. These specimens included a single wall, a coupled wall, and a C-shaped core-wall. The main objective was to develop post-tensioned C-shaped timber core-walls for tall timber buildings with enhanced lateral strength and stiffness. To better understand the timber compressive stress distributions at the wall base, particle tracking technology (PTT) technology was applied for the first time to investigate the behaviour of the compression toe. Previous post-tensioned timber testing primarily used the displacement measurements to determine the timber compressive behavior at the wall base or rocking interfaces. However, by using PTT technology, the timber strain measurements in the compression zone can be much more accurate as PTT is able to track the movement of many particles on the timber surface. This paper presents experimental testing results of post-tensioned CLT walls with a focus on capturing timber compressive behavior using PTT. The PTT measurements were able to better capture small base rotations which occurred at the onset of gap opening and capture unexpected phenomena in core-wall tests. The single wall test result herein presented indicates that while the MMBA could predict the moment rotation behavior with reasonable accuracy, the peak strain response was under predicted in the compression toe. Further detailed study is required to better understand the complex strain fields generated reflective of the inherent cross-thickness inhomogeneity and material variability of CLT.

Images, eqnz.chch.2010

20140522_8951_EOS M-22 Demolition Of what many in Christchurch know as the Millers building, but for many recent years was the home to the Christchurch City Council, till just a week or two before the first earthquake of 2010. Now, in mid-2014 it is finally being demolished after nearly 45 months empty. A bus is leaving the new (temporary) bu...