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%
Recent research in the field of assessment of hygrothermal response has focused on either laboratory experimentation or modelling, but less work has been reported in which both aspects are combined. Such type of studies can potentially offer useful information regarding the benchmarking of models and related methods to assess hygrothermal performance of wall assemblies.
This report documents the experimental results of a benchmark experiment that was designed to allow benchmarking of stud drying predicted by NRC’s an advanced hygrothermal computer model called hygIRC, when subjected to nominally steady-state environmental conditions. hygIRC uses hygrothermal properties of materials derived from tests on small-scale specimens undertaken in the laboratory. The drying rates of wall assembly featuring wet studs that result from moisture accumulated during the framing stage of a 5 or 6 storey building. The drying rate of those studs was assessed in an experiment undertaken in a controlled laboratory setting. The results were subsequently used to help benchmark hygIRC reported under separate cover.
The charring behavior of timber structural elements, such as the charring rate of timber elements and delamination of glue-laminated timber, affects the structural stability of timber buildings. The charring rate of timber elements varies depending on the severity of fire exposure. However, charring rates have been ordinarily investigated in...
Cross-Laminated Timber (CLT) is a new engineered wood material that was introduced in the past decade as a promising candidate to build structures over 10 stories. So far, a handful of tall CLT buildings have been built in low seismic regions around the world. Full-scaled seismic shaking table tests revealed the vulnerability of this building type when resisting seismically-induced overturning. This study proposes a new analysis and design approach for developing overturning resistance for platform CLT buildings. New structural detailing is proposed to alter the moment-resisting mechanism and ...
A research project was undertaken to investigate the behaviour of composite CLT slabs with glulam downstands cut back from the supports. A desk study and Finite Element Modelling (FEM) were used and evaluated on their ability to model and design such a structure, focusing on the cut back location and utilising reinforcement screws...
This paper describes a series of three full-scale furnace tests on post-tensioned LVL box
beams loaded with vertical loads, and presents a proposed fire design method for post-tensioned timber members. The design method is adapted from the calculation methods given in Eurocode 5 and NZS:3603 which includes the effects of changing geometry and several failure mechanisms specific to posttensioned timber. The design procedures include an estimation of the heating of the tendons within the timber cavities, and relaxation of post-tensioning forces. Additionally, comparisons of the designs and assumptions used in the proposed fire design method and the results of the full-scale furnace tests are made. The experimental investigation and development of a design method have shown several areas
which need to be addressed. It is important to calculate shear stresses in the timber section, as shear is much more likely to govern compared to solid timber. The investigation has shown that whilst tensile failures are less likely to govern the fire design of post-tensioned timber members, due to the axial compression of the post-tensioning, tensile stresses must still be calculated due to the changing centroid of the members as the fire progresses. Research has also highlighted the importance of monitoring additional deflections and moments caused by the high level of axial loads.