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.
Glued laminated timber (glulam) is manufactured by gluing and stacking timber lamellas,
which are sawn and finger-jointed parallel to the wood grain direction. This results in a
sustainable and competitive construction material in terms of dimensional versatility and
load-carrying capacity. With the proliferation of glued timber constructions, there is an
increasing concern about safety problems related to adhesive bonding. Delaminations are
caused by manufacturing errors and in service climate variations simultaneously combined
with long-sustained loads (snow, wind and gravel filling on flat roofs). Several recent
building collapses were related to bonding failure, which should be prevented in the future
with a timely defect detection. As an outlook, the feasibility of air-coupled ultrasound tomography was demonstrated with numerical tests and preliminary experiments on glulam. The FDTD wave propagation model was excited by the difference of the time-reversed sound fields transmitted through a test and a reference (defect-free) glulam cross-section. Both datasets were obtained with the same SLT setup. Wave convergences then provided a map of bonding defects along the height and width of the inspected glulam cross-sections. Further
research is envisaged in this direction
New Zealand Society for Earthquake Engineering Conference
April 13-15, 2012, Christchurch, New Zealand
Driven by sustainability, locally available resources and expertise, and economy, the design of the Carterton Events Centre focused on timber for the majority of the main structural and non-structural components. Combined with a client desire for minimization of earthquake damage, dissipative post-tensioned rocking...
This report was commissioned to review and formulate strategies for the accelerated uptake and
social acceptance of living in multi-storey cross-laminated timber (CLT)-constructed buildings in infill developments to: remove cultural barriers, meet the sustainability expectations of potential buyers and obtain a better understanding of how we can facilitate the rapid introduction of this innovative construction technology in Australia.
An extensive review of literature within the field was conducted to gather an overview of the
barriers that inhibit consumers, governments and industry in the uptake and acceptance of CLTconstructed buildings for infill development. Data was collected on CLT buildings worldwide, to build a comprehensive picture of multi-storey timber buildings using CLT-construction systems.
The objective of this project was to quantify and compare the environmental impacts associated with alternative designs for a typical North American mid-rise office building. Two scenarios were considered; a traditional cast-in-place, reinforced concrete frame and a laminated timber hybrid design, which utilized engineered wood products (cross-laminated timber (CLT) and glulam). The boundary of the quantitative analysis was cradle-to-construction site gate and encompassed the structural support system and the building enclosure. Floor plans, elevations, material quantities, and structural loads associated with a five-storey concrete-framed building design were obtained from issued-for-construction drawings. A functionally equivalent, laminated timber hybrid design was conceived, based on Canadian Building Code requirements. Design values for locally produced CLT panels were established from in-house material testing. Primary data collected from a pilot-scale manufacturing facility was used to develop the life cycle inventory for CLT, whereas secondary sources were referenced for other construction materials. The TRACI characterization methodology was employed to translate inventory flows into impact indicators. The results indicated that the laminated timber building design offered a lower environmental impact in 10 of 11 assessment categories. The cradle-to-gate process energy was found to be nearly identical in both design scenarios (3.5 GJ/m2), whereas the cumulative embodied energy (feedstock plus process) of construction materials was estimated to be 8.2 and 4.6 GJ/m2 for the timber and concrete designs, respectively; which indicated an increased availability of readily accessible potential energy stored within the building materials of the timber alternative.
The paper discusses experimental and numerical seismic analyses of typical connections and wall systems used in cross-laminated (X-Lam) timber buildings. An extended experimental programme on typical X-Lam connections was performed at IVALSA Trees and Timber Institute. In addition, cyclic tests were also carried out on full-scale single and coupled X-Lam wall panels with different configurations and mechanical connectors subjected to lateral force. An advanced non-linear hysteretic spring to describe accurately the cyclic behaviour of
connections was implemented in ABAQUS finite element software package as an external subroutine. The FE model with the springs calibrated on single connection tests was then used to reproduce numerically the behaviour of X-Lam wall panels, and the results were compared with the outcomes of experimental full-scale tests carried out at IVALSA. The developed model is suitable for evaluating dissipated energy and seismic vulnerability of X-Lam structures.
Cross Laminated Timber (CLT), which is made by laminating dimension lumber at right
angles, is an innovative high-performance building material that offers many positive attributes
including renewability, high structural stability, storage of carbon during the building life, good
fire resistance, possibility of material recycling and reuse. It is conceptually a sustainable and
cost effective structural timber solution that can compete with concrete in non-residential and
multi-family mid-rise building market. Therefore, there is a need to understand and quantify the
environmental attribute of this building system in the context of North American resources,
manufacturing technology, energy constraints, building types, and construction practice. This
study is to compare energy consumption of two building designs using different materials, i.e.
CLT and concrete.
Wood-frame is the most common construction type for residential buildings in North America. However, there is a limit to the height of the building using a traditional wood-frame structure. Cross-laminated timber (CLT) provides possible solutions to mid-...
Cross-laminated timber panel buildings are gaining a growing interest of the scientific community due to significant technical advantages, such as the material sustainability, the high fire resistance and quickness of erection. Nevertheless, it is well known that timber panels themselves are not able to dissipate a significant amount of energy during an earthquake. In fact, in this system the seismic design is carried out in order to
dissipate the energy by means of inelasticity of connections. Generally, the elements devoted to withstand plastic deformations are the panel-panel and panel-foundation joints and, therefore, their ability to sustain repeated excursion in plastic range governs the building inelastic response. The paper here presented aims to propose an advanced approach for designing cross laminated timber panel buildings. In particular, it is proposed to substitute the classical hold-downs, which usually exhibit a limited dissipation capacity, with an innovative type of dissipative angle bracket. The new connections, called dissipative L-stub, apply the concept usually adopted for designing the hysteretic metallic dampers ADAS (Added Damping and Stiffness). In particular, their tapered shape allows a better spread of lasticization resulting in a high dissipation capacity. Within this framework, in order to characterize the force-displacement response under cyclic loads of L-stubs an experimental campaign is carried out. Afterwards, the effectiveness of the proposed approach is proved by analysing the non-linear response under seismic loads of a three-storey building alternatively equipped with hold-downs or L-stub. Finally, the response of classical and innovative system is compared in terms of behaviour factor.
This research investigates the fire behaviour of laminated veneer lumber elements
and cross-laminated timber panels. The study focused on some research questions
regarding the fire resistance of unprotected and protected timber structural elements,
the possibility to predict accurately the fire behaviour of timber elements through numerical modelling, and the accuracy of analytical estimations of fire resistance using simplified design methods. Experimental tests of small and large specimens exposed to fire on one or more sides and subjected to different types and levels of load were performed. The results highlight the good performance of timber structural elements in fire conditions. The collected data were used to validate two- and three-dimensional models implemented in the general purpose finite element code Abaqus. Thermal and mechanical analyses were carried out to estimate the temperature distribution within unprotected and protected cross-sections
of different sizes, the fire resistance and the displacement of timber elements loaded inplane and out-of-plane