New Zealand Society for Earthquake Engineering Conference
April 13-15, 2012, Christchurch, New Zealand
The Nelson Marlborough Institute of Technology Arts and Media building was completed in 2011 and consists of three seismically separate complexes. This research focussed on the Arts building as it showcases the use of coupled post-tensioned timber shear walls. These are part of the innovative Expan system. Full-scale, in-situ dynamic testing of the novel building was combined with finite element modelling and updating to obtain an understanding of the structural dynamic performance within the linear range. Ambient testing was performed at three stages during construction and was combined with forced vibration testing for the final stage. This forms part of a larger instrumentation program developed to investigate the wind and seismic response and long term deformations of the building. A finite element model of the building was formulated and updated using experimental modal characteristics. It was shown that the addition of non-structural elements, such as cladding and the staircase, increased the natural frequency of the first mode and the second mode by 19% and 24%, respectively. The addition of the concrete floor topping as a structural diaphragm significantly increased the natural frequency of the first mode but not the second mode, with an increase of 123% and 18%, respectively. The elastic damping of the NMIT building at low-level vibrations was identified as being between 1.6% and 2.4%
On October 23rd 2007, a seven storey Cross Laminated Timber building was tested on the world’s largest earthquake shake table at Miki near Kobe in Japan. Cross laminated timber construction and the preliminary earthquake and fire tests are overviewed. The huge E-Defense shake table facility in Japan and the test building are described and the earthquake records used to test the building. The building performed well when subjected to the severe Kobe earthquake record. It had some minor softening and no residual deformation. Accelerations measured within the building were large and need further design consideration.
The NMIT Arts building completed in 2011 in Nelson is the first three storey building using Expan type technology with energy dissipating rocking shear walls constructed from laminated veneer lumber (LVL). The long term wall post tensioning, wall shortening, and concrete composite floor deformations have been evaluated in more detail from April 2011 until October 2011. An overview is given of the building and overall instrumentation systems. Detail is given on the long term instrumentation on-site data logging systems, data transfer, Auckland monitoring equipment, data extraction and development of the web interface. The instrumentation is temperature sensitive but gross variations are predictable and corrected. The data will provide further opportunity to investigate hygro-thermal response. Preliminary results for the rate of compressive deformation were 0.4 to 1.4 mm in five months till mid October 2011 and the post tension loss is between 8 and 14.5 kN over the same five months. The post-tension losses since June 2010 vary from 13.9 to 20.6%.