Cross-laminated timber, also known as X-Lam or CLT, is well established in
Europe as a construction material. Recently, implementation of X-Lam products and
systems has begun in countries such as Canada, United States, Australia and New
Zealand. So far, no relevant design codes for X-Lam construction were published in
Europe, therefore an extensive research on the field of cross-laminated timber is being
performed by research groups in Europe and overseas. Experimental test results are
required for development of design methods and for verification of design models
accuracy.
This thesis is part of a large research project on the development of a software
for the modelling of CLT structures, including analysis, calculation, design and
verification of connections and panels. It was born as collaboration between Padua
University and Barcelona"s CIMNE (International Centre for Numerical Methods in
Engineering). The research project started with the thesis “Una procedura numerica per
il progetto di edifici in Xlam” by Massimiliano Zecchetto, which develops a software,
using MATLAB interface, only for 2D linear elastic analysis. Follows the phase started
in March 2015, consisting in extending the 2D software to a 3D one, with the severity
caused by modelling in three dimensions. This phase is developed as a common project
and described in this thesis and in “Pre-process for numerical analysis of Cross
Laminated Timber Structures” by Alessandra Ferrandino.
The final aim of the software is to enable the modelling of an X-Lam structure in
the most efficient and reliable way, taking into account its peculiarities. Modelling of
CLT buildings lies into properly model the connections between panels. Through the
connections modelling, the final aim is to enable the check of preliminarily designed
connections or to find them iteratively, starting from hypothetical or random
connections.
This common project develops the pre-process and analysis phases of the 3D
software that allows the automatic modelling of connections between X-Lam panels. To achieve the goal, a new problem type for GiD interface and a new application for
KRATOS framework have been performed. The problem type enables the user to model
a CLT structure, starting from the creation of the geometry and the assignation of
numeric entities (beam, shell, etc.) to geometric ones, having defined the material, and
assigning loads and boundary conditions. The user does not need to create manually the
connections, as conversely needs for all commercial FEM software currently available;
he just set the connection properties to the different sides of the panels. The creation of
the connections is made automatically, keeping into account different typologies of
connections and assembling of Cross-Lam panels. The problem type is special for XLam structures, meaning that all features are intentionally studied for this kind of
structures and the software architecture is planned for future developments of the postprocess phase.
It can be concluded that sound bases for the pre-process and analysis phases of
the software have been laid. However, future research is required to develop the postprocess and verification phases of the research project.
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...
The study investigates the environmental benefits of reusing Cross Laminated Timber (CLT) panels. The Global Warming Potential (GWP) of a single-stored Coffee shop built in 2016 in Kobe city was calculated, considering different CLT reuse ratios, forest land-use and material substitution possibilities. The results showed that as the rate of reused CLT panel increases the total GWP decreases. Moreover, in all cases, the option with smallest GWP is when the surplus wood is used for carbon storage in the forest, revealing the importance of a growing forest for increasing the environmental benefits of timber utilisation. The results suggest the systematic reuse of CLT panels offers a possibility to increase the carbon stock of Japanese Cedar plantation forests and further mitigate the environmental impact of construction.
Eucalyptus grandis is South Africa‘s most important commercial hardwood species. The availability of E. grandis and its fast growth rate creates the opportunity to explore its uses further. Cross-laminated timber (CLT) is a prefabricated multilayer engineered panel product made of at least three layers, with the grain direction of some or all of the consecutive layers orthogonally orientated. In order to add value to E. grandis, reduce the export of low-cost chips, increase the profit margins of local plantation owners and create jobs, the development of E. grandis CLT in South Africa may be an option. There is concern among some researchers that the bonding quality evaluation tests proposed by CLT standards have been developed for glulam and are too severe for CLT. These researchers proposed that further analysis and possibly even revision of the test methods should be considered. There is also a need to evaluate the mechanical properties of CLT panels made of E. grandis to completely understand the structural performance of these panels, including their bond quality and durability, and therefore be able to rely on E. grandis CLT as a construction material. The objectives of this study were: . To evaluate the face-bonding quality of CLT panels from E. grandis timber bonded with a one component polyurethane resin; . To determine the influence of material and processing parameters on the face-bonding quality of CLT manufactured from E. grandis timber bonded with a one component polyurethane resin; . To analyse different testing methods for evaluating the face-bonding quality of CLT. The design for this experiment consisted of eight groups with different combinations of parameters for density, grooves and pressure per group. Four different testing methods were used to evaluate the face-bonding quality of CLT panels from E. grandis and to determine the effect of parameters on face-bonding quality: A delamination test on 100 x 100 mm block specimens (Test A), a shear test on 40 x 40 mm specimens (Test B), a shear test on 40 x 40 mm specimens with grain direction 45° to load direction (Test C) and a combined delamination and shear test on 70 x 70 mm specimens with grain direction 45° to load direction (Test D). Results of the statistical analysis indicated that E. grandis CLT made with 1C-PUR adhesive can obtain excellent face-bonding quality using a clamping pressure of 0.7 MPa and with no stress relief grooves present. All samples passed the shear test (Test B) which is the reference test method proposed by EN 16351 (2015). It was found that a strength component and durability component will be an advantage when testing the bond quality of CLT. Shear tests at 45° to the load direction did not completely eliminate the rolling shear effect. The combined delamination and shear test (Test D), seems to have potential as a good test for bond quality since it is a combination of a durability and shear strength test. There are still questions about the relative advantages of specific test methods for bond quality, especially on the effect of rolling shear. Further work should focus on this aspect and the use of stress models might be a way of gaining further insights.
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