An economic-design optimization of cross-laminated timber (CLT) plate with stiffening ribs is presented. For the structural analysis, an enhanced assumed strain (EAS) solid finite element is used. It behaves well for thin plates (with no shear locking) and delivers reasonable approximations for the transverse shear stresses in layered composites. Eurocodes 5 (EC5) are followed in defining the optimization constraints, which include deflections, stresses and fundamental eigenfrequency. The gradient optimization is performed. Analytical expressions for sensitivities are obtained by an automatic differentiation tool. The result is an economic timber plate configuration that complies with the EC5 requirements. Numerical examples are presented in order to illustrate the approach.
Up to now, structural sealant glazing façades have been extensively applied. They are at the cutting edge of technology and meet the highest standards. The objective of several research projects was to develop stiffening glass fronts, which replace expensive frameworks or wind bracings behind the large glass windows. Thus, potential applications...
The objective of this study was to examine new attributes and conduct economic analyses for composite CLT (CCLT) and value-added appearance-based CLT products manufactured with varying substitution of softwood lumber with structural composite lumber (SCL) and hardwood lumber. Incentives for including such materials could be aesthetic, structural and economic.
Structural and aesthetic property assessments were carried out on prototype CLT panels. Multiple CLT panel configurations (17) were evaluated to assess the effects of including hardwood and SCL materials in the layups. Presence of hardwood in the panels’ configuration generally led to higher checking and density. Because of the higher shrinkage of hardwood, the bondline suffered from more delamination. A lower density hardwood (aspen) was included in some configurations and exhibited a greater direct compatibility with current Canadian manufacturing process. Changes to this process, such as selecting a hardwood specific adhesive may lead to improvements.
Cross Laminated Timber (CLT) is an extremely strong engineered wood panel intended for roof, floor, or wall applications. Currently there is little research comparing CLT to steel and concrete, materials CLT hopes to replace This research uses a detailed literary analysis on CLT and case study on Carbon12, a recently constructed CLT structure in Portland, Oregon, to compare the cost and schedule requirements of CLT with a cast-in-place concrete slab. The case study consisted of a detailed analysis of Carbon12, interview with Scott Noble, senior project manager for Carbon12, and a detailed schedule and cost analysis. Results showed that for a concrete floor system used on Carbon12, material costs were far less than costs for a CLT floor system and labor costs were far greater than costs for a CLT floor system. For the schedule analysis, results showed that a concrete floor system would add an additional 10 weeks to the construction schedule of Carbon12. These results led to the conclusion that CLT is a feasible building material for dense, urban, mid-rise structures similar to Carbon12. The quick installation time, small crew, and environmental benefits of CLT outweigh the added costs of the material.
Glued glass front constructions have long been in use and are generally considered the state of the art. However, with these solutions the glass serves no stiffening or bearing function, but merely functions as an outer cover. The objective of several research projects was to investigate alternative constructions of stiffening glass fronts, which...
North American cross laminated timber is currently made of softwood lumber following the guidelines of the ANSI/APA PRG-320 manufacturing standard. In this study, the potential of manufacturing CLT panels using various hardwood species and engineered wood products (EWP) was investigated for their compatibility and the impact on the dimensional stability and aesthetics of the end products. Yellow birch, trembling aspen, sugar maple, laminated strand lumber (LSL) and laminated veneer lumber (LVL) were compared to 100% spruce-pine-fir group species (SPF) lumber made CLT panel. The bond line performance of the assemblies was tested as well as the dimensional stability and appearance of the panels when subjected to conditions with equilibrium moisture contents (EMC) of 4.5%, 12% and 16%. Results showed that higher density hardwood species were prone to delamination. LSL, LVL and trembling aspen yielded promising delamination results. Best overall dimensional stability results were achieved with EWP inclusive configurations. Aesthetic integrity assessment showed that the use of hardwood for the core layer and edge gluing of softwood outer layers had a negative impact. Overall, the study showed a great potential for manufacturing future composite CLT (CCLT) products using EWP and low density hardwood species. The cost premium of using these alternative materials would need to be offset by valuable sets of properties or by a reduction of the manufacturing cost.
Wood is a pure, sustainable, renewable material. The increasing use of wood for construction can improve its sustainability. There are various techniques to assemble multi-layer wooden panels into prefabricated, load-bearing construction elements. However, comparative market and economy studies are still scarce. In this study, the following assembling techniques were compared: laminating, nailing, stapling, screwing, stress laminating, doweling, dovetailing, and wood welding. The production costs, durability, and ecological considerations were presented. This study was based on reviews of published works and information gathered from 27 leading wood product manufacturing companies in six European countries. The study shows that the various techniques of assembling multi-layer wooden construction panel elements are very different. Cross laminated timber (CLT) exhibited the best results in terms of cost and durability. With regard to ecological concerns, dovetailing is the best. Taking into account both durability and ecological considerations, wooden screw-doweling is the best. These alternatives give manufacturers some freedom of choice regarding the visibility of surfaces and the efficient use of lower-quality timber. CLT is the most cost-effective, is not patented, and is a well-established option on the market today.