Advanced Wood-Based Solutions for Mid-Rise and High-Rise Construction: Structural Performance of Post-Tensioned CLT Shear Walls with Energy Dissipators
The latest developments in seismic design philosophy have been geared towards developing of so called "resilient" or "low damage" innovative structural systems that can reduce damage to the structure while offering the same or higher levels of safety to occupants. One such innovative structural system is the Pres-Lam system that is a wood-hybrid system that utilizes post-tensioned (PT) mass timber components in both rigid-frame and wall-based buildings along with various types of energy disspators. To help implement the Pres-Lam system in Canada and the US, information about the system performance made with North American engineered wood products is needed. That information can later be used to develop design guidelines for the designers for wider acceptance of the system by the design community.Several components influence the performance of the Pres-Lam systems: the load-deformation properties of the engineered wood products under compression, load-deformation and energy dissipation properties of the dissipators used, placement of the dissipators in the system, and the level of post-tensioning force. The influence of all these components on the performance of Pres-Lam wall systems under gravity and lateral loads was investigated in this research project. The research project consisted of two main parts: material tests and system tests.
International Convention of Society of Wood Science and Technology
Research Status
Complete
Notes
June 23-27, 2014, Zvolen, Slovakia, p.761-768
Summary
The mission of the Hardwood Scanning Center at Purdue University is to increase the
global competitiveness of the United States hardwood industry and to conserve the
hardwood resource by development of manufacturing technologies which will enable
hardwood industry to “see inside a tree” and use this information to make better
processing decisions.
The Hardwood Scanning Center partnered with Microtek, GmbH of Italy in the
development of an industrial grade log CT scanner. World’s first three industrial CT log
scanners have been installed in last 12 months in mills around the world and we will
briefly discuss their application. The Hardwood Scanning Center also developed
visualization and optimization software for the hardwood veneer and sawmill operations.
This presentation will provide an overview of state-of-the-art in CT scanning of logs.
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.
Until now we developed an estimation method for strength distributions of laminated veneer lumber (LVL) element by nonlinear least-squares method (NLM). Estimated strengths by this method were modulus of elasticity (MOE) and modulus of rupture (MOR) in the horizontal use direction and the vertical use direction, tensile strength and compression strength. But to use LVL for structural members, shear strength was also needed. Therefore, we tried to estimate the shear strength distribution of LVL element by NLM same as MOE and MOR in the horizontal use direction and the vertical use direction, the tensile strength of LVL and the compression strength of LVL in the previous reports. We conducted shear strength test for LVL and estimated element shear strength distribution by LVL strength data in the horizontal and vertical use direction. Next, we simulated LVL shear strength distribution using element shear strength distribution and compared with experimental ones in each use direction. They were overlapped in both use direction. Therefore, we could validate NLM for estimating element shear strength distribution.
The effect of glass fiber reinforced polymer (GFRP) on the technical properties of LSL made from poplar (Populus deltoids L.) employing pMDI and UF as binders was investigated. Technical properties such as modulus of rupture (MOR), Modulus of elasticity (MOE), shear strength (SS), compression strength parallel to the grains (CS //), impact strength (IS), water absorption (WA) and thickness swelling (TS) were determined. Results confirmed that resin type and GFRP have significant effects on the LSL properties. It was revealed that the most beneficial effect of GFRP is on MOR, MOE, IS, SS and CS respectively. The Highest properties were obtained by using pMDI as the resin and GFRP as the reinforcement, where properties such as MOR, MOE, IS, SS and CS were improved by 123, 114, 100, 94, and 90%, respectively, compared to control samples. Furthermore, GFRP incorporation led to alteration of fracture place from tension side to compression side. Depending on the treatment type, the WA and TS values of the LVLs improved between 23% to 68% and 19.5% to 78%, respectively.
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