Results from a series of blast tests performed in October 2016 on three two-story, single-bay cross-laminated timber (CLT) structures demonstrated the ability of CLT construction to resist airblast loads in a predictable fashion. These tests were performed on structures without superimposed load to limit inertial resistance. Subsequently, a follow-on series of tests was performed to investigate the response of axially-loaded CLT construction. Panels damaged during the preceding test were removed and replaced. Axial load was applied using precast concrete blocks to simulate the loaded condition of a five-story building at the first-floor front panel of the structures. These test structures were exposed to two shots: the first was designed to keep the structures within their respective elastic ranges while the second was designed to push the structures beyond their elastic limits. Reflected pressure and peak deflections were recorded at the front panels of the test structures to document the two-way panel load distribution behavior under a dynamic load event and the clearing of the shock wave. Prior to conducting the blast tests, a small number of tests were performed on a load tree test apparatus to aid in test planning by investigating the post-peak response of individual CLT panels of various lengths to quasi-static out-of-plane and axial loads applied simultaneously. This paper provides an overview of the results obtained from both the quasi-static and blast tests of axially-loaded CLT. Additionally, the paper compares CLT structure, component, and connection response across the suite of data. Conclusions are offered to assist engineers in the design of load bearing CLT construction exposed to airblast loads.
New Zealand Society for Earthquake Engineering Conference
April 27-29, 2017, Wellington, New Zealand
Multi-storey timber structures are becoming progressively desirable owing to their aesthetic and environmental benefits and to the high strength to weight ratio of timber. A recent trend in timber building industry is toward cross laminated timber (CLT) panelized structures. The shake table tests within the SOFIE project have shown that the CLT buildings constructed with traditional methods can experience high damage especially at the connections which generally consist of hold-down brackets and shear connectors with mechanical fasteners such as nails or bolts. Thus, current construction methods are not recognised as reliable in seismic prone areas. The main objective of this project is to develop a new low damage structural concept using innovative resilient slip friction (RSF) damping devices. The component test results demonstrate the capacity of this novel joint for dissipating earthquake energy as well as self-centring to minimize the damage and the residual drift after a severe event. The application of RSF joints as holddown connectors for walls were investigated through numerical studies. Moreover, a core wall system comprised of cross laminated timber and RSF connectors is subjected to time-history earthquake simulations. The numerical results exhibit no residual displacement alongside a significant reduction in peak acceleration which can be attributed to significant amount of dissipated seismic energy over the RSF joints within the system.
Small furnace fire tests were conducted on CLT cladded with calcium silicate boards, gypsum boards, and combinations of the two. The difference in fire resistance when using different board types, combinations, and thicknesses was demonstrated. Some cross-sectional configurations had enough 2-hour fire resistance performance...
Cross laminated timber (CLT) is a versatile engineered timber product that is increasingly well-known and of global interest in several applications such as full size plane or linear timber elements. The aim of this study involves investigating the performance of CLT beams loaded in-plane by considering bending and shear stress analysis with a special emphasis on the in-plane shear behavior including the complex internal structure of CLT. Numerical analysis based on 3D-FE models was used and compared with two existing analytical approaches, namely representative volume sub element (method I) and composite beam theory (method II). The separate verification of bending and shear stresses including tree different shear failure modes was performed, and a good agreement was obtained. The main difference between the results relates to shear failure mode in the crossing areas between the orthogonally bonded lamellas in which the distribution of shear stresses tzx over the crossing areas per height of the CLT beam is not in accordance with the analytical assumptions. The presented analyses constitute the first attempt to contribute to the on-going review process of Eurocode 5 with respect to CLT beams loaded-in plane. Currently, regulations on designing these types of beams do not exist, and thus experimental and numerical investigations are planned in the future.
An extensive body of research is currently available on the behaviour of concrete and steel structures when subjected to blast threats, however, little to no details on how to address the design or retrofitting of wood structures are available. In this paper, preliminary results, both experimental and analytical, are presented on the flexural behaviour of glulam beams under high strain rates. A total of three 80 mm x 228 mm x 2,500 mm glulam beams with a clear span of 2,235 mm were subjected to simulated blast loads using a shock tube. The preliminary experimental results showed that a brash tension failure mode was observed on the tension laminate. It was also shown that a simplified SDOF model, using linear elastic resistance curves, was capable of predicting the failure displacement and level of damage with reasonable accuracy.