The high performance in-plane of cross laminated timber (CLT) panels has created a potential for the use of CLT members act as diaphragms in steel structures. The behaviour of this diaphragm system depends strongly on the connections involved in linking the panels together and to the steel members. A study of the connections at both locations was made using experimental testing of two connection designs for the panel-to-panel case, and the development of a staggered lag screw connection for the panel-to-steel beam case. The results showed good performance for the double spline and fully-threaded inclined screws panel-to-panel connections. The lag screw connection showed high strength, stiffness, and ductility. The CSA Standard O86-09 was found to best predict the strength of both types of connections. Characteristic design stiffness values were presented for the stiffness at low levels of displacement and the initial, elastic stiffness.
Traditional wood-wood connections, widely used in the past, have been progressively replaced by steel fasteners and bonding processes in modern timber constructions. However, the emergence of digital fabrication and innovative engineered timber products have offered new design possibilities for wood-wood connections. The design-to-production workflow has evolved considerably over the last few decades, such that a large number of connections with various geometries can now be easily produced. These connections have become a cost-competitive alternative for the edgewise connection of thin timber panels. Several challenges remain in order to broaden the use of this specific joining technique into common timber construction practice: (1) prove the applicability at the building scale, (2) propose a standardized construction system, (3) develop a convenient calculation model for practice, and (4) investigate the mechanical behavior of wood-wood connections. The first building implementation of digitally produced through-tenon connections for a folded-plate structure is presented in this work. Specific computational tools for the design and manufacture of more than 300 different plates were efficiently applied in a multi-stakeholder project environment. Cross-laminated timber panels were investigated for the first time, and the potential of such connections was demonstrated for different engineered timber products. Moreover, this work demonstrated the feasibility of this construction system at the building scale. For a more resilient and locally distributed construction process, a standardized system using through-tenon connections and commonly available small panels was developed to reconstitute basic housing components. Based on a case-study with industry partners, the fabrication and assembly processes were validated with prototypes made of oriented strand board. Their structural performance was investigated by means of a numerical model and a comparison with glued and nailed assemblies. The results showed that through-tenon connections are a viable alternative to commonly used mechanical fasteners. So far, the structural analysis of such construction systems has been mainly achieved with complex finite element models, not in line with the simplicity of basic housing elements. A convenient calculation model for practice, which can capture the semi-rigid behavior of the connections and predict the effective bending stiffness, was thus introduced and subjected to large-scale bending tests. The proposed model was in good agreement with the experimental results, highlighting the importance of the connection behavior. The in-plane behavior of through-tenon connections for several timber panel materials was characterized through an experimental campaign to determine the load-carrying capacity and slip modulus required for calculation models. Based on the test results, existing guidelines were evaluated to safely apply these connections in structural elements while a finite element model was developed to approximate their performance. This work constitutes a firm basis for the optimization of design guidelines and the creation of an extensive database on digitally produced wood-wood connections. Finally, this thesis provides a convenient design framework for the newly developed standardized timber construction system and a solid foundation for research into digitally produced wood-wood connections.
Project contacts are Linda Zimmer and Cory Olsen at the University of Oregon
During the testing and fabrication of mass timber projects a natural byproduct inevitably occurs in the form of offcuts and cutouts. In the case of new mass timber structures, the engineered wood materials are typically fabricated and prepared off site, allowing for the majority of the leftover materials to be made into useful products at the same facility already ideally set up for further digital fabrication. While the thickness of many of the spare panelized elements under investigation/production at TDI might seem excessive for smaller scale elements, the digital design and production techniques already being used allow for a fine degree of precision commensurate with furniture joinery. We propose to experiment with designing and fabricating furniture scale components and furniture prototypes as a way to reclaim these otherwise unused timber products. This project captures off cuts and remaindered materials from structural testing at TDI in both CLT and MPP panels.
Our focus is the design and fabrication of freestanding furnishings (ex: stools, benches, tables, chairs) that will exploit the technologies available at the Emmerson Lab. We come at this with two perspectives: in the first, products could be made directly from the materials available; in the second, the output will act as a formwork or “jig” to facilitate construction of an entirely new prototype that could expand into additional material languages. In either case it is important to us to share digital files of prototypes as “open source” designs so that production facilities and design professionals can work together to reduce waste and/or use our designs as a springboard to customize their own pieces. In this way we address the stated program goals to expand and develop new products and building components and to foster markets for these. Our iterative approach to digital design and digital hybrids utilizes CNC/robotic fabrication and assembly and we will be testing our ideas in a design-build format.