Forest Service/USDA Wood Innovations Grants
Recipient Point of Contact: Emily Dawson
Location: Portland, Oregon
Summary
PathHouse’s mission is to provide permanent affordable housing – at scale – for low income and disaster-impacted communities through deployment of mass timber modular residences. PathHouse is designing and implementing an innovative housing production system that will be capable of producing upwards of 100,000 affordable housing units annually using regional wood fiber, and state-of-the-art manufacturing and design expertise. This grant would assist in funding the applied research required to fabricate and test the first PathHouse prototype modules. The structural design of the module system aims for optimum efficiency from a wood fiber standpoint, and utilizes mass timber panels with very thin profiles, between 1” and 3” thick. Mass timber panels produced in the Pacific Northwest (PNW) offer the potential for efficiencies of scale, speed, and safety unparalleled by other construction techniques, and with significantly lower embodied energy. The region is strongly positioned to succeed economically in this industry, due to recognized global leadership in research and development of engineered wood products, and abundant timber resources. We aim to demonstrate that there is room for growth in the market for thinner-profile mass timber products with thinner lamination dimensions. A consistent market for high-value use of small-diameter trees would support the increasing need for restoration forestry projects.
Forest Service/USDA Wood Innovations Grants
Recipient Point of Contact: Stefan Schneider
Location: Portland, Oregon
Summary
CutMyTimber, a wood and mass timber fabricator since 2010, is seeking funding to research and develop a Modular Mass Timber Skeleton (MMTS) system with accompanying software. Mass timber includes innovative and structurally engineered wood products such as glue-laminated beams (GLB) and cross-laminated timber (CLT). Glulam beams consist of layers of dimensional lumber, bonded together with moisture-resistant adhesives. Pound for pound, this product is stronger than steel. Despite growing interest among builders and investors, developing a mass timber building currently involves too much time and uncertainty due to lack of knowledge and experience. Our team will draw from two decades worth of experience in successful mass timber projects to develop a system of standard and engineered connections that will be made available to the industry.
The project goals are to:
(1) research and optimize a standard, yet modular, skeleton system of glulam and connection hardware based on potential load scenarios, number of levels in the structure, grid distances, etc.
(2) produce an available design guide detailing standardized, engineered solutions
(3) review and obtain structural approval of all standard connection types by partnering with engineers and fire safety and code compliance experts
(4) develop and release the MMTS system in an intuitive and free-to-use software tool in partnership with software designers. This will be made available for early-stage design by the mass timber industry.
CutMyTimber expects the MMTS system will reduce the market barriers of risk, time, and cost of mass timber projects at all levels, including design, engineering, fabrication, and installation. In turn, we expect to stimulate and expand opportunities for the mass timber building market in the United States.
In this study, the life cycle environmental implications of modular multi-storey building with cross-laminated timber (CLT) volumetric elements are analysed, considering the product, construction, service life, end-of-life and post-use stages. A bottom-up attributional approach is used to analyse the environmental flows linked to the global warming potential (GWP), acidification potential (AP) and eutrophication potential (EP) impacts of the building for a 50-year reference study period. The result shows that the building’s life cycle impacts can vary considerably, depending on the energy production profile for the operation of the building. The product, construction and end-of-life stages constitute a significant share of the life cycle impacts, and the importance of these stages increase as the energy production profile evolves towards a low-carbon energy mix. For the GWP, the product and construction stages constitute 13% of the total life cycle impact when the operational energy is based on a coal-based marginal electricity. The contribution of this stage increases to 81% when electricity is based on a plausible long-term Swedish average mix. The patterns of the life cycle EP and AP impacts are also closely linked to the energy production profile for the assessment. The analysis shows that a 5% reduction in the GWP impact in the product stage is achievable with emerging solutions for the improved structural design of CLT buildings. This study highlights the need for strategies to improve the life cycle environmental profile of modular CLT buildings.
Cross-laminated timber (CLT) modular construction possesses the advantages of wood, such as excellent carbon storage and thermal insulation, and of modular construction, such as considerably reduced construction period and cost as well as high productivity. This study evaluates the hygrothermal performance of CLT walls considering modular construction in future climatic conditions. Firstly, CLT walls with plywood applied to a core layer were manufactured. A mock-up of a CLT building was produced and its construction process was analyzed. Hygrothermal behavior of the CLT walls was simulated using WUFI simulation program, and the predicted results were verified against measurements obtained from the mock-up experiment. Finally, the hygrothermal performance of the CLT wall was evaluated for four types of insulation and future climate in eight cities of USA. The coefficient of variation—root mean square error (CV(RMSE))—of the temperature and relative humidity inside the ply-lam CLT wall from mock-up experiments and simulation evaluation were 6.43% and 7.02%, respectively, which met the validation criteria. Based on the hygrothermal performance, the ply-lam CLT wall with extruded polystyrene insulation was evaluated as safe from moisture problems in all the eight cities considered in this study. However, the risk of mold growth in all regions and insulation types increased under climate change with a rise of average annual temperature.
Wooden construction constitutes a specific branch of the building industry that focuses on high-quality materials, a developed sense of aesthetics connected with comfort and functionality, and concern for ecology and durability. This type of construction has a positive effect on human quality of life. This article focuses on modular frame construction and technological aspects of wooden houses built according to Canadian or Scandinavian technologies. Taking weather conditions of Scandinavian countries into consideration, timber is a popular building material, which, when preserving certain parameters such as density of rings, may provide durability of a modular wooden building even up to 200–300 years. This article is a review and presents the possibility of producing frame buildings in Europe (Poland) in accordance with the applicable standards, including a heat transfer coefficient U = 2 [W/(m²·K]. In Poland, wooden frame buildings can be traced back to the 14th century. Wooden frame buildings and modular wooden frame buildings were produced even earlier in Norway. Wooden construction continued in the mid-1800s in various forms (with wooden filling and/or panels). In the mid-1900s (1941), certain dimensioning became regulated by law, which then applied to different types of insulation fillings. Prefabricated modular wood frame houses were common in the 1960s.
Throughout the last two decades the timber building sector has experienced a steady growth in multi-storey construction. Although there has been a growing number of research focused on trends, benefits, and disadvantages in timber construction from various technical perspectives, so far there is no extensive literature on the trajectory of emerging architectural typologies. This paper presents an examination of architectural variety and spatial possibilities in current serial and modular multi-storey timber construction. It aims to draw a parallel between architectural characteristics and their relation to structural systems in timber. The research draws from a collection of 350 contemporary multi-storey timber building projects between 2000 and 2021. It consists of 300 built projects, 12 projects currently in construction, and 38 design proposals. The survey consists of quantitative and qualitative project data, as well as classification of the structural system, material, program, massing, and spatial organization of the projects. It then compares the different structural and design aspects to achieve a comprehensive overview of possibilities in timber construction. The outcome is an identification of the range of morphologies and a better understanding of the design space in current serial and modular multi-storey mass timber construction.
As mass timber becomes increasingly popular in the United States and around the world, there comes more demand for mass timber in larger buildings. With this demand comes a necessity for these buildings to be able to withstand seismic forces; and in some locations, these forces can get quite high. Typical mass timber lateral systems (such as CLT shear walls) have worked fine for lower seismic forces and shorter buildings, but with this new demand comes a need for newer systems. Rocking timber walls is one of these systems. The goal of a rocking timber wall is to allow the lateral wall system to move in the case of high seismic force, thus reducing the loading the wall experiences. This is done with vertical post tensioning (PT) within cross-laminated timber panels (CLT). In addition, easily replaceable energy dissipation devices, such as U-shaped flexural plates (UFPs), allow for concentration of inelastic deformation during rocking of the walls, which keeps the CLT and PT components free from harm. Another system used to handle seismic load in tall mass timber structures are inter-story isolation systems. These systems can isolate the force at separate levels, effectively decreasing the load the foundation takes from the building's movement. Even newer than these systems is the Floor Isolated Re-centering Modular Construction System (FIRMOC), which utilizes rocking timber walls, inter-story isolation, and the addition of prefabricated modular mass timber to create a system capable of effectively and efficiently dealing with large seismic forces. This report seeks to present these innovative, capable, and effective lateral systems for seismic forces in large scale mass timber structures in a manner that provides understanding of how they work and what makes them effective.
Cross laminated timber volumetric construction (CLTVC) is an innovative construction technology that combines the sustainability of timber and the efficiency of modular construction, as opposed to conventional construction. However, the connection installing methods of CLTVC, such as fastening, are laborious with limited accessibility for connection installations, thus hindering the application of CLTVC in mid- and high-rise structures. Therefore, a new way of connecting CLT modules by sliding and stacking is explored herein with a proposed damage-control interlocking connection system, aiming to provide a more efficient assembly solution to CLTVC that does not require onsite screwing. Quasi-static monotonic and cyclic test, and numerical analyses were conducted to assess the mechanical performance of the proposed connections, which possessed adequate translational stiffness and strength of the proposed connections. The connections' ability to control deformation – damage is moved away from timber and the embedded fasteners, was also well demonstrated in the test, as both screws and timber remained mostly intact after testing. The proposed connection design showcases a new concept of modules’ assembly in volumetric construction with higher efficiency and flexibility; meanwhile demonstrates the potential in reducing the permanent damage to structural materials during service life and enabling reuse.
Forest Service/USDA Wood Innovations Grants
Recipient Point of Contact: Sarah Horton
Location: Portland, Oregon
Summary
World Forestry Center (WFC) requests USFS funds to support the Design Development, costing, and Construction Document phases for a new Forestry Experience Center. The goal of this project is to create a demonstration site for scalable, factory-made mass timber buildings that will act as a model for building technologies that advance solutions to climate change. WFC is a 501(c)3 non-profit organization headquartered in Portland, Oregon, and located in Portland’s Washington Park, which attracts over 3 million visitors each year. Our mission is to create and inspire champions of sustainable forestry. Our programs are designed to shape a society that values and takes action in support of the economic, ecological, and social benefits of forests. The new 27,300 square-foot Forestry Experience Center will include an exhibit hall, event space, a café, office space, and a “gateway” structure that will connect Washington Park visitors to WFC, Washington Park, Forest Park, and beyond. WFC has been working with Sidewalk Labs as a design consultant to incorporate Sidewalk Labs’ prefabricated modular mass timber building elements into early conceptual design. The new building will demonstrate how these products can be adopted at scale across the construction sector for mid-rise buildings, with competitive costs on par with expectations for timber or other conventional materials, and with greater environmental and social benefits. Interactive, emotionally-resonant exhibits on forestry’s most urgent challenges will be the focal point of programming within the new Forestry Experience Center. The building itself will serve as a tool to drive a public narrative about the benefits of prefabricated mass timber construction. The design will be enhanced by interpretive elements that will connect visitors to the products and techniques employed throughout the structure and the role these innovations play in improving the health of our forests and quality of life in our communities.
The construction industry is one of the largest producers of greenhouse gases, accounting for 38% of global carbon emissions. Recently, interest in mass timber construction has grown, due to its potential benefits in reducing environmental impact compared to traditional construction methods that use steel and concrete, and in promoting global sustainability and climate agendas, such as the Sustainable Development Goals (SDGs) and global net-zero emissions by 2050. Despite the slow adoption of mass timber construction (MTC) in Australia, some innovative and iconic projects and initiatives have been realised. The research intends to identify critical challenges and potential for broader adoption of MTC in Australia. The study reviewed selected MTC projects, followed by a perception survey and interviews of the relevant industry stakeholders in Australia to understand the key barriers and enablers for the widespread application of MTC in Australia. Significant challenges identified in the research include a lack of understanding of fire safety, regulations, performance, inherent application, and local manufacturers and suppliers, which are yet to be improved. In addition, it was found that prior experience built confidence in the application of MTC. Furthering widespread adoption of MTC technology in Australia beyond cost competitiveness requires the Australian construction industry to work towards developing suitable regulatory and insurance policies, financing, incentivising clients, and a skilled workforce. The study focuses on an investigation in the context of industry perceptions of MTC in Australia. Based on the analysis of the critical characteristics of MTC projects, and using the empirical data, the study identifies key challenges and opportunities in the widespread application of MTC in Australia.
Friction-based dampers are a valid solution for non-invasive seismic retrofitting interventions of existing structures, particularly reinforced-concrete (RC) structures. The design of friction-based dampers is challenging: underestimating the slip force prevents the full use of the potential of the device, which attains the maximum admissible displacement earlier than expected. By contrast, overestimating the slip force may cause delayed triggering of the device when the structure has suffered extensive damage. Therefore, designing the appropriate slip force is an optimization problem. The optimal slip force guarantees the highest inter-story drift reduction. The authors formulated the optimization problem for designing a specific class of friction-based dampers, the asymmetric friction connection (AFC), devised as part of the ongoing multidisciplinary Horizon 2020 research project e-SAFE (Energy and Seismic AFfordable rEnovation solutions). The seismic retrofitting technology involves the external application of modular prefabricated cross-laminated timber (CLT) panels on existing external walls. Friction dampers connect the CLT panels to the beams of two consecutive floors. The friction depends on the mutual sliding of two metal plates, pressed against each other by preloaded bolts. This study determines the optimal slip force, which guarantees the best seismic performance of an RC structural archetype. The authors investigate the nonlinear dynamic response of a coupled mechanical system (RC frame-friction damper) under a set of strong-motion earthquakes, using non-differential hysteresis models calibrated on the experimental cyclic responses. The solution of the optimization leads to the proposal of a preliminary simplified design procedure, useful for practitioners.
Limited empirical and qualitative studies focus on the detailed processes and obstacles for coordinating off-site prefabrication between builders and suppliers. This research aims to identify and address the obstacles that currently prevent the further expansion of off-site prefabrication, with a research scope on timber and mechanical/electrical/plumbing (MEP) services in construction projects. The focal point of this research is to highlight their obstacles. A total of forty interviews were conducted and analyzed from four builders’ organizations and four suppliers’ organizations to ascertain their obstacles in coordinating the practice of off-site prefabrication. The results found the builder’s obstacles were sustainability, quality assurance (QA), mass production, CAD/BIM, technological support, commercial arrangements, system building, buffering in supply, schedule monitoring, productivity, flexibility, engagement, risks, and multiple supply arrangements. The supplier’s obstacles were design, financing and subcontracting, coordination, recognized practices, risks, multiple supply arrangements, and constraints. Moreover, the builders and suppliers had identified some ways to harmonize off-site prefabrication of timber. Some examples of timber prefabrication technology include joinery, doors and/or windows, structural floor/wall/roof frames, partitions, trusses, stairs, balustrades, and others. MEP services with in situ construction comprise the use of power sources and working coordination. The most important outcome of this investigation is that these obstacles can be addressed through collaboration and coordination. This is because there is a traditionally a lack of collaboration amongst builders and their suppliers. Furthermore, there is a lack of coordination between them in general. The research contributes to the improved timber and MEP services collaboration and coordination in off-site prefabrication, which can be referred to by other approaches of modular construction.
Forest Service/USDA Wood Innovations Grants
Recipient Point of Contact: Mark Weaver
Location: Glendale, California
Summary
Buildings used by many federal agencies including the Department of State (DOS) and Department of Defense (DOD) often must meet blast, ballistic, and forced entry (FE) design requirements to mitigate physical hazards associated with terrorism. Historically, these buildings have used concrete and steel construction to protect occupants from these threats. However, the emergence of mass timber construction, particularly cross-laminated timber (CLT), presents a sustainable, modular, and cost-effective alternative building material for high-security infrastructure. Previous studies involving blast, ballistic, and FE testing on CLT indicated that CLT provides much greater protection than conventional wood construction but that it needs some form of reinforcement to comply with more stringent antiterrorism requirements and broaden the use of wood structures in federal facilities. The proposed effort builds on the results of a previous Wood Innovation Grant (21-DG-11052021-242) that constructed full-scale CLT panels with steel reinforcement and tested these panels under quasi-static four-point bending testing. This effort involves two types of investigation to further demonstrate the effectiveness of reinforced CLT panels under extreme conditions: (1) weathering and (2) blast. The weathering testing will investigate whether reinforced CLT panels maintain their dimensional stability and do not delaminate under exposure to temperature cycling and moisture conditions during construction. Ideally, the blast testing will demonstrate the ability of reinforced CLT to exhibit a ductile post-peak response as well as be capable of supporting its axial load following a blast event. A primary focus of the proposed effort will be to ensure the developed reinforced CLT panel designs are competitive with existing DOS-compliant protection construction systems from both a cost and weight perspective. The project team includes an American CLT manufacturer (SmartLam) to quickly assess the cost impacts associated with a reinforced CLT. Additionally, representatives from the DOS that are familiar with federal facility protective design requirements will be consulted to ensure programmatic, procurement, and detailing issues are considered during reinforced CLT panel design development.
International Conference on New Advances in Civil Engineering
Research Status
Complete
Series
IOP Conference Series: Materials Science and Engineering
Summary
Related to sustainability movement and minimizing the carbon footprint, timber structures are becoming more attractive. Wood, as main structural material, offers many benefits relate mostly to economic and ecological aspects, compared to other materials as steel or concrete. On the other hand, physical characteristics of wood complicate the usage of a timber for high-rise or large-span structures. It brings a new challenge for architects and engineers to deliver feasible solution for usability of timber, despite its features. One of the possible solutions could be implementation of CLT (Cross-Laminate Timber) panels in structural systems developed earlier for buildings made of prefabricated concrete slabs. SOM in cooperation with Oregon State University are currently testing composite slabs made of CLT and thin concrete layer reinforcing the wood and protecting it from fire. Although the system solution looks promising, and could bring the result, slabs limit using of the space in layout. On the other hand, frame structures would be much more efficient. This article comes up with an idea of modular frame structure, which could help to solve the problem. The scheme is based on "gridshell" type systems, where rods form a more efficient shell for dealing with stress forces.
This project studied the effect of openings on the lateral performance of CLT shear walls
and the system behavior of the walls in a module. Three-layer Cross Laminated Timber
(CLT) was used for manufacturing the wall and module specimens. The laminar was
Spruce-Pine-Fir (SPF) #2&Better for both the major and minor layers. Each layer was 35
mm thick. The panel size was 2.44 m × 2.44 m.
Four configurations of walls were investigated: no opening, 25% opening, 37.5% opening,
and 50% opening. The opening was at the center of the wall and in the shape of a square.
A CLT module was made from two walls with 50% openings, with an overall thickness of
660 mm. The specimens were tested under monotonic loading and reverse-cyclic loading,
in accordance with ASTM E564-06 (2018) and ASTM E2126-19.
The wall without opening had an average peak load of 111.8 kN. It had little internal
deformation and the failure occurred at the connections. With a 25% opening, deformation
within the wall was observed but the failure remained at the connections. It had the same
peak load as the full wall. When the opening was increased to 37.5%, the peak load
decreased by 6% to 104.9 kN and the specimens failed in wood at the corners of the
opening. Further increasing the opening to 50%, the peak load dropped drastically to 63.4
kN, only 57% of the full wall.
The load-displacement relationship was approximately linear until the load reached 60%
of the peak or more. Compared to the full wall, the wall with 25% opening had 65% of the
stiffness. When the opening increased to 37.5% and 50%, the stiffness reduced to 50% and
24% of the full wall, respectively. The relationship between stiffness and opening ratio was
approximately linear. The loading protocol had effect on the peak load but not on the
stiffness. There was more degradation for larger openings under reverse-cyclic loading.
The performance of the module indicated the presence of system effect that improves the
ductility of the wall, which is important for the seismic performance of the proposed
midrise to tall wood buildings. The test data was compared to previous models found in
literature. Simplified analytical models were also developed to estimate the lateral stiffness
and strength of CLT wall with openings.
The two primary considerations for construction project management are budget and time management. Modular construction has the potential to improve construction productivity by minimizing time and costs while improving safety and quality. Cross-Laminated Timber (CLT) panels are beneficial for modular construction due to the high level of prefabrication, adequate dimensional stability, and good mechanical performance that they provide. Accordingly, CLT modular construction can be a feasible way to speed up the construction and provide affordable housing. However, an in-depth study is needed to streamline the logistics of CLT modular construction supply chain management. CLT modular construction can be performed by two primary means based on type of modules produced: panelized (2D) and volumetric (3D). This research aims to help the Architecture, Engineering, and Construction (AEC) industry by developing a tool to assess the impact of various logistical factors on both panelized and volumetric modular construction productivity. Discrete-Event Simulation (DES) models were developed for panelized and volumetric CLT modular construction based on a hypothetical case study and using data collected from superintendents and project managers. Sensitivity analysis is conducted using the developed models to explore the impact of selected manufacturing and logistical parameters on overall construction efficiency. Comparing volumetric and panelized simulations with the same number of off-site crews revealed that the volumetric model has lower on-site process duration while the off-site process is significantly longer. Accordingly, from manufacturing to the final module assembly, the total time for the volumetric model is longer than panelized model. Moreover, the simulations showed that volumetric modular construction is associated with less personnel cost since the main process is performed off-site, which has lower labor costs and a smaller number of crews required on-site. This framework could be used to identify the optimum construction process for reducing the time and cost of the project and aid in decision-making regarding the scale of modularity to be employed for project.
This paper presents an integrated design tool for structures composed of engineered timber panels that are connected by traditional wood joints. Recent advances in computational architecture have permitted to automate the fabrication and assembly of such structures using Computer Numerical Control (CNC) machines and industrial robotic arms. While several large-scale demonstrators have been realized, most developed algorithms are closed-source or project-oriented. The lack of a general framework makes it difficult for architects, engineers and designers to effectively manipulate this innovative construction system. Therefore, this research aims at developing a holistic design tool targeting a wide range of architectural applications. Main achievements include: (1) a new data structure to deal with modular assemblies, (2) an analytical parametrization of the geometry of five timber joints, (3) a method to generate CNC toolpath while integrating fabrication constraints, and (4) a method to automatically compute robot trajectories for a given stack of timber plates.
The presented research describes the holistic development of a modular lightweight timber shell. So-called segmented timber shells approximate curved geometries with the use of planar plates, thus combining the excellent structural performance of double curved shells with the resource-efficient prefabrication of timber modules using only planar elements. Segmented timber shells constitute a novel building system that demands for innovative approaches on structural design and construction technologies. The geometric complexity of plate shells in conjunction with the particularities of the building material wood pose great challenges to the computational design and planning processes as structural requirements and fabrication constraints determine the shell design at early design phases. This paper discusses the design development and construction of the BUGA Wood Pavilion: A segmented timber shell structure made of hollow cassette components. Particular emphasis lies on the technical challenges of the employed building system, notably structural design and analysis, detailing solutions and the construction process. The authors further describe the integrative structural design and optimization methods developed for the timber shell in question. The BUGA Wood Pavilion demonstrates the possibilities of lightweight and sustainable wood architecture merging the merits of integrative design, structural engineering and high-tech robotic fabrication methods.
This paper presents an innovative and sustainable timber constructive system that could be used as an alternative to traditional emergency housing facilities. The system proposed in this study is composed of prefabricated modular elements that are characterized by limited weight and simple assembly procedures, which represent strategic advantages when it comes facing a strong environmental disaster (e.g. an earthquake). The complete dismantling of structural elements and foundations is granted thanks to specific details and an innovative connection system called X-Mini, capable of replacing traditional anchoring devices (i.e. hold downs and angle brackets) by resisting both shear and tension loads. This constructive system, denoted as Hybrid Timber Frame (HTF), takes advantage of the strong prefabrication, reduced weight of light-frame timber systems, and of the excellent strength properties of the Cross Laminated Timber (CLT) panels. Specifically, the solid-timber members typically used in the structural elements of light-frame systems are replaced by CLT linear elements. The results of experimental tests and numerical simulations are critically presented and discussed, giving a detailed insight into the performance of the HTF under seismic conditions.
The presented research describes the holistic development of a modular lightweight timber shell. So-called segmented timber shells approximate curved geometries with the use of planar plates, thus combining the excellent structural performance of double curved shells with the resource-efficient prefabrication of timber modules using only planar elements. Segmented timber shells constitute a novel building system that demands for innovative approaches on structural design and construction technologies. The geometric complexity of plate shells in conjunction with the particularities of the building material wood pose great challenges to the computational design and planning processes as structural requirements and fabrication constraints determine the shell design at early design phases. This paper discusses the design development and construction of the BUGA Wood Pavilion: A segmented timber shell structure made of hollow cassette components. Particular emphasis lies on the technical challenges of the employed building system, notably structural design and analysis, detailing solutions and the construction process. The authors further describe the integrative structural design and optimization methods developed for the timber shell in question. The BUGA Wood Pavilion demonstrates the possibilities of lightweight and sustainable wood architecture merging the merits of integrative design, structural engineering and high-tech robotic fabrication methods.
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