Laminated Wood Research Articles

State-of-the-Art Review of Moisture Content Sensor Deployment in Mass Timber Construction

State-of-the-Art Review of Moisture Content Sensor Deployment in Mass Timber Construction

Adaptive Reuse for Building Above Our Cities: Evaluating the Feasibility of Mass Timber Vertical Extensions

Adaptive Reuse for Building Above Our Cities: Evaluating the Feasibility of Mass Timber Vertical Extensions

Introduction to special issue—advances in mass timber structures

Introduction to special issue—advances in mass timber structures

Comparison of mass timber structure and RC structure with regard to sustainability by life cycle assessment

Since the 18th-century Industrial Revolution, high-rise have played a crucial role in addressing urbanization challenges, remaining a primary solution for urban living. However, this architectural advancement has also contributed to environmental decline. Presently, steel and concrete stand out as the predominant materials for high-rise construction, with well-documented significant carbon emissions. This paper delves into the potential of timber as an environmentally friendly alternative in high-rise construction to address such environmental concerns. Furthermore, it examines the impact of these structures on land load. The paper conducts a comprehensive review of life cycle assessment (LCA) studies and offers a comparative analysis of the climate change impacts associated with timber versus conventional materials like reinforced concrete (RC), underscoring the urgent need for sustainable development in the vertical expansion of our cities. The findings demonstrate that both the mass and carbon emissions of high-rise timber structures, in comparison to RC structures, can be reduced by approximately half. The paper aims to underscore the benefits of timber in comparison to conventional reinforced concrete methods, thereby informing material selection in favor of sustainable urban development.

Residential long-span timber floor typologies: a comprehensive performance assessment and opportunities for value adding to plantation hardwood

ABSTRACT High-performance engineered wood products (EWPs) and composite mass timber products (CMTPs) are being employed more frequently in residential projects with increasing interest in more sustainable systems that achieve long-spans. The relative performance of these systems is not readily apparent, with individual manufacturers offering proprietary products assembled from specific timber resources. In addition, the suitability of producing these long-span systems using plantation hardwoods is currently unknown. This research investigated the comparative performance of four typical EWPs and CMTPs; 1. solid slab, 2. thin-walled cassette, 3. T-sections, and 4. slab on beam. Key performance metrics of depth, mass, stiffness, vibration response, fire performance and global warming potential were assessed. The mechanical performance of two high-strength plantation hardwood varieties (Eucalyptus nitens and Eucalyptus globulus) were determined experimentally and subsequently used to re-calculate performance criteria for the previously assessed typologies. Substantial improvements over the typical softwood varieties were identified, particularly in structural efficiency, global warming potential and fire performance. This highlights the potential for value adding to plantation hardwoods by using them in high-performance long-span engineered floor products.

Comparison of Embodied Carbon Footprint of a Mass Timber Building Structure with a Steel Equivalent

The main purpose of this study is to quantify and compare the embodied carbon (EC) from the materials used or designed to build the Adohi Hall, a residence building located on the University of Arkansas campus in Fayetteville, AR. It has been constructed as a mass timber structure. It is compared to the same building design with a steel frame for this study. Based on the defined goal and scope of the project, all materials used in the building structure are compared for their global warming potential (GWP) impact by applying a life cycle assessment (LCA) using a cradle-to-construction site system boundary. This comparative building LCA comprises the product stage (including raw material extraction, processing, transporting, and manufacturing) plus transportation to the construction site (nodule A1–A4, according to standard EN 15804 definitions). In this study, GWP is primarily assessed with the exclusion of other environmental factors. Tally®, as one of the most popular LCA tools for buildings, is used in this comparative LCA analysis. In this study, the substitution of mass timber for a steel structure with a corrugated steel deck and concrete topping offers a promising opportunity to understand the GWP impact of each structure. Mass timber structures exhibit superior environmental attributes considering the carbon dioxide equivalent (CO2 eq). Emissions per square meter of gross floor area for mass timber stand at 198 kg, in stark contrast to the 243 kg CO2 eq recorded for steel structures. This means the mass timber building achieved a 19% reduction in carbon emissions compared to the functional equivalent steel structure within the building modules A1 to A4 studied. When considering carbon storage, about 2757 tonnes of CO2 eq are stored in the mass timber building, presenting further benefits of carbon emission delays for the life span of the structure. The substitution benefit from this construction case was studied through the displacement factor (DF) quantification following the standard process. A 0.28 DF was obtained when using mass timber over steel in the structure. This study provides insights into making more environmentally efficient decisions in buildings and helps in the move forward to reduce greenhouse gas (GHG) emissions and address GWP mitigation.

EXPERIMENTAL STUDY ON THE WOODEN MEMBER CONNECTION METHOD IN SEISMIC PANEL DAMPERS FOR STEEL STRUCTURES

Recently, government of Japan has encouraged using forest resources to expand the use of timber. Although moderate-or large-scale buildings are generally steel constructed structures, the authors proposed using cross-laminated timber (CLT) as support members for seismic panel damper systems. The benefits of employing mass timber as support members include the effective utilization of forest resources and a reduction in the building weight. To investigate the shear transfer performance between the shear panel damper and the mass timber, 16 specimens were meticulously prepared. Based on the test results, steel types such as H-shaped steel, circular tube, cruciform steel and steel plate were shown to be effective as the shear connector. In cases where H-shaped steel, circular tubes, and cruciform steel are utilized as shear connectors, significant labor is required for welding to the H-shaped steel and cutting into the mass timber, demanding time and effort from workers. Ensuring the shear connector section has high stiffness is crucial to maintain the energy dissipation capacity of the shear panel. Steel plates offer an advantage in their flexibility to control both strength and stiffness through the size of the plate used.

EXPERIMENTAL STUDY ON THE WOODEN MEMBER CONNECTION METHOD IN SEISMIC PANEL DAMPERS FOR STEEL STRUCTURES

Recently, government of Japan has encouraged using forest resources to expand the use of timber. Although moderate-or large-scale buildings are generally steel constructed structures, the authors proposed using cross-laminated timber (CLT) as support members for seismic panel damper systems. The benefits of employing mass timber as support members include the effective utilization of forest resources and a reduction in the building weight. To investigate the shear transfer performance between the shear panel damper and the mass timber, 16 specimens were meticulously prepared. Based on the test results, steel types such as H-shaped steel, circular tube, cruciform steel and steel plate were shown to be effective as the shear connector. In cases where H-shaped steel, circular tubes, and cruciform steel are utilized as shear connectors, significant labor is required for welding to the H-shaped steel and cutting into the mass timber, demanding time and effort from workers. Ensuring the shear connector section has high stiffness is crucial to maintain the energy dissipation capacity of the shear panel. Steel plates offer an advantage in their flexibility to control both strength and stiffness through the size of the plate used.

Comparison of using two LCA software programs to assess the environmental impacts of two institutional buildings

The current trends in climate change have captured the attention of stakeholders across multiple industries, including the building sector. With the introduction of innovative building materials such as mass timber products (MTPs), it has become essential to evaluate their environmental performance. In response, a variety of life cycle assessment (LCA) software programs are available to meet this need. However, it is crucial to understand how different LCA software and databases might influence the results. This study was aimed at exploring the impact of two widely used LCA software programs, SimaPro and Athena Impact Estimator, on LCA results. Two buildings were employed to conduct this study, a traditional institutional building and a mass timber building currently under construction. By comparing the numerical outputs from both software programs, it was discovered that while both could reach similar conclusions regarding the environmental impacts of a building, their use is limited to comparative purposes only. The software programs produced distinct numerical values in their outputs and attributed the sources of impacts differently, indicating they cannot be used interchangeably. However, either SimaPro or Athena Impact Estimator was suitable for estimating the global warming potential of a building during stages A1 to A3.

Nonlinear analysis model of the progressive damage of aluminum–wood sandwich structures under high-speed impact conditions

The impact responses of various protective structures composed of 2A12 aluminum alloy and wood laminates were studied experimentally. The experiments were conducted using different impact energies. By varying the sandwich material thickness and using two different bullet shapes, the effects of the sandwich material’s damage process and the core layer thickness on the protective performance were studied. The multilayer structure’s core layer failure condition was determined using the improved 3D Hashin criterion and a finite element model was established using Abaqus software. Tensile and three-point bending tests were conducted and the progressive damage model was verified statically. The model was then verified dynamically using the Hopkinson bar test. The mechanical properties of the materials under high dynamic strain rates were obtained through action loading testing of the specimens at different loading rates. The loading waveform was analyzed and a stress-strain relationship diagram was drawn at various strain rates. By verifying the experimental data, a numerical model that could capture the deformation and failure details during crushing was established, and the composite target plate impact failure mode and the trajectory change law were described. This study could lead to use of a new impact damage prediction method for laminates.

Numerical parametric study of cross-laminated timber diaphragms under in-plane loading

Cross-Laminated Timber (CLT) is a mass timber product that has gained recognition as a viable structural product for tall and large structures. While CLT provides several advantages, such as being eco-friendly, lightweight, and improving thermal insulation compared to other primary structural materials, its application in the horizontal diaphragms, specifically for floors and roofs, has not been thoroughly investigated. This paper presents the development of a detailed finite element (FE) model capable of simulating the response of CLT diaphragms under in-plane loading. The accuracy of the developed models was evaluated through comparison with available experimental data. Additionally, a comprehensive parametric study was conducted to examine the influence of various factors, including connection stiffness, boundary condition, panel installation pattern, and panel thickness, on the in-plane deflection of the CLT diaphragm. The research indicates that panel-to-panel connections play a more critical role in determining the stiffness of CLT structures than panel-to-beam connections. Furthermore, it was demonstrated that the deflection of CLT panels was influenced by different parameters depending on the orientation of the applied load. When the load is applied perpendicular to the panel length, panel thickness influences the diaphragm deformation. Conversely, when the load is applied parallel to the panel length, the panel-to-panel connection stiffness has a more significant effect on the deformation of the diaphragm. Findings also revealed that staggered CLT panel layouts provided more load distribution and higher capacity compared to non-staggered layouts when the load was applied perpendicular to the panel length.

Characterization of Asoka (Saraca Indica L.) branch wood for pulp and paper manufacturing

Asoka (Saraca indica L.) branch wood was evaluated for its chemical composition, morphological features, kraft pulping behavior, and physical properties. The Asoka used in this study contained low amounts of cellulose and hemicellulose, but higher amounts of lignin and ash. It was found that the morphological indices of Asoka branch wood were mostly adequate for pulping and papermaking. The pulping of this wood was performed using chemi-mechanical pulping (CMP), conventional kraft pulping, and soda pulping processes under different conditions, i.e., active alkali and anthraquinone (AQ) addition. The results showed that alkaline pupling and CMP provided low screened yield values. Acceptable kappa numbers and reject levels were obtained at 22% active alkali of soda and kraft-AQ pulpings. CMP pulp showed higher brightness and screened yield than that of alkaline pulps. Alkaline pulpings of Asoka branch wood provided slightly different strength properties of paper sheets than those of CMP pulp. Based on the findings, it can be concluded that Asoka branch wood is more suitable as a raw material for mechanical pulping than it is for alkaline pulping.

Meta-analysis of temperature, heat release rate, delamination and auto-extinction of timber compartments

A meta-analysis was conducted on 100 structural mass timber compartment fire experiments. The analysis investigated temperature, heat release rate, auto-extinction and delamination. Dissimilarities in the compartment geometry, ventilation, and exposed timber surfaces of these experiments could be accounted for using two parameters, α and %AO (applicable to near cubic, ventilation-controlled compartments) defined as the shape-modified ventilation factor and opening ratio. The correlation coefficient for the total heat release rate (HRR) with the area of timber for the large and medium scale data was 0.97 and 0.74, respectively. Similarly, the correlation of medium scale data for the contribution of timber to the heat release rate was 0.90. A statistical analysis revealed a higher probability for auto-extinction to occur for exposure levels below 20%. Above 20% exposure, the risk for sustained flaming and delamination increase substantially. Auto-extinction was shown to depend strongly on delamination, with a 93% probability of occurrence given no delamination. The use of PUR HBS adhesive was shown to cause delamination in 73% of the cases, with PUR HBX delaminating in 33% of cases.

Design Analysis of Mass Timber and Volumetric Modular Strategies as Counterproposals for an Existing Reinforced Concrete Hotel

Design Analysis of Mass Timber and Volumetric Modular Strategies as Counterproposals for an Existing Reinforced Concrete Hotel

Impact of Insulation Strategies of Cross-Laminated Timber Assemblies on Energy Use, Peak Demand, and Carbon Emissions

Cross-Laminated Timber (CLT) panels have many structural benefits but do not have much thermal resistance. We have developed a solution to insulate CLT structures that uses high-performance insulation panels that provide R-values up to R40/inch. The CLT panels are made of layers of wood laminates (three, five, seven or more). The solution replaces some of the wood laminates in the CLT production with the insulation panels in a staggered fashion so that the wood laminates maintain contact throughout the panel, ensuring the CLT panel’s structural integrity. The insulated CLT panels have factory-installed water-resistive barriers reducing the installation time by eliminating installing insulation and water-resistive barriers on site. Per simulations, the CLT/insulation panel achieved code-required insulation levels with commonly available insulation materials. The significance of the thermal mass of CLT/insulation hybrid building envelopes was quantified by comparing the whole building energy performance and peak demand of traditional low mass and CLT wall assemblies resulting in up to 7% reduction in peak demand for cooling in Knoxville, TN, in a multifamily building. Buildings contribute over 40 percent of carbon emissions. The proposed CLT/insulation hybrid building envelope addresses both operational and embodied carbon by having high thermal resistances due to the embedded insulation sections and eliminating the use of high embodied carbon materials such as steel and concrete. The carbon benefit is estimated.

High‐fidelity finite element modeling of the seismic response of prefabricated steel stairs

AbstractAdvancing the seismic resilience of building systems is an active area of research in earthquake engineering. Ensuring safe egress in and out of buildings during extreme events, such as an earthquake, is essential to supporting this effort. To this end, understanding the seismic response of stairs facilitates the robust design of egress systems to ensure they can remain operable after an earthquake. From prior earthquake events and physical experiments, it is understood that stairs with a flight to landing fixed connection at multiple levels within a building are prone to damage. In addition, the stair system with flight to landing fixed attachments may affect the dynamic behavior of the building. To accommodate seismic inter‐story drifts, a kinematically free connection between the stairs and landing has been proposed. Herein this connection is referred to as a drift‐compatible stair connection. To investigate and aid in the design of such a connection, a unique set of shake table experiments were conducted at the University of Nevada, Reno. In this paper, an overview of these tests is presented, and a high‐fidelity finite element model of the tested stair system is used to predict the responses measured during these experiments. Developed in Abaqus, the robustness of the modeled stair unit is investigated considering a variety of contrasting connections, namely, drift‐compatible connections, fixed ends and one end fixed and the other free. Results from these numerical simulations offer guidance towards development of simplified models of multi‐level stair subsystems. Such models are needed when investigating seismic resilience of building systems across a wider range of hazard levels. Furthermore, best practices observed utilizing the models developed and evaluated herein against experimental data will be useful for subsequent analysis of larger stair tower models, such as the 10‐story stair system implemented in the NHERI Tall Wood mass timber building with post‐tensioned rocking walls, conducted in 2023 at the UC San Diego Large High‐Performance Outdoor Shake Table.

Monotonic testing of single shear-plane CLT-to-CLT joint with hardwood dowels

Reducing embodied carbon emissions in buildings and striving for carbon neutrality through sustainable design has become a primary goal in the construction industry. The industry is expanding its use of wood-engineered products, such as cross-laminated timber (CLT) to achieve those sustainability goals. Furthermore, replacing steel fasteners with lower embodied carbon alternatives is gaining increased attention in timber engineering. This paper aims to quantify the mechanical behavior of single shear-plane CLT-to-CLT joints using hardwood dowels. The study includes 154 single shear-plane experimental tests with four different CLT species, two hardwood dowel species, and two dowel diameters. The test specimens were subjected to cyclic and monotonic loading until failure, and mechanical properties such as yielding and ultimate strength, serviceability and yielding stiffness, and ductility were quantified. The hardwood dowel CLT-to-CLT joints demonstrated high strength with up to 10.3 kN (2.3 kips) capacity per dowel and lateral stiffness of up to 5.2 kN/mm (30.8 k/in) per dowel. This strength and stiffness are roughly equivalent to or exceed values for mass timber wood screws, making hardwood dowels a good alternative. In addition, the observed mean ductility of joints ranged from 2.4 to 4.5. Finally, analytical equations for the joints' yielding strength, lateral serviceability stiffness, and yielding stiffness were derived with non-linear regression analysis and validated using the experimental test results.

A New Moment-Resisting Glulam Beam-End Connection Utilizing Mechanically Fastened Steel Rods—An Experimental Study

A new moment-resisting mass timber connection was designed based on the principles of force equilibrium in applied mechanics. The connection configuration utilizing two mechanically fastened threaded steel rods embedded into the end of a glulam beam section was experimentally investigated in this study. A gradually increasing transverse load was applied to the free end of a cantilevered beam, causing a bending moment on the beam-end connection until failure. Four different connection configurations were examined, each replicated twice to verify results. The beam connection parameters investigated were rod anchorage length (200 and 250 mm) and square washer size (38.1 and 50.8 mm). Test results show that increasing the washer size increased the connection bending strength by increments more significantly than those due to increasing the rod anchorage length. However, the connection configurations with the smaller-size washer, which failed mainly due to wood crushing under the washer, had higher ductility ratios than those with the larger-size washer, which failed due to steel rod yielding. In a real-life scenario, a structural element such as a glulam beam is usually loaded to approximately 50% to 70% of its design capacity, considering a reasonable margin of safety. The study estimates a maximum possible bending moment utilization factor for the strongest connection configuration that ranged between 34% and 48% compared to the maximum moment resistance of a supported glulam beam spanning an average length of 4.0 m to 6.0 m (a common span length in framed timber buildings) and has a cross-section size same as the one utilized in this study. This utilization factor is quite large for a timber connection, and thus, confirms a considerable moment-resisting capability of the new configuration developed in this study.

Analysis of location, feedstock availability, and economic impacts of potential mass timber processing facilities in Michigan

Mass timber, an engineered wood product, offers exceptional strength and versatility as a building material, is lightweight, which makes it easy to transport and assemble, is aesthetically appealing, and offers the potential to reduce GHG emissions. This study attempts to identify the potential locations for mass timber production in Michigan, estimate the available feedstock, and evaluate the economic impacts of mass timber production on the state's economy. Procurement zones for all softwood lumber producers in Michigan were identified and overlaid to create competition hotspots for the softwood sawtimber industry. Two potential locations were identified for mass timber production within the state. Forest Inventory and Analysis (FIA) data was used to estimate the annual sustainable availability of softwood (ASAW) for mass timber production. Finally, IMPLAN was used to assess the economic impacts associated with mass timber production in Michigan. We identified two sawmills for mass timber production and concluded that there is sufficient ASAW for mass timber production in these facilities. Producing 12,429 m3 of mass timber supports at least 93 total jobs (35 direct, 29 indirect, and 29 induced) with a total output of $12.52 million in Michigan's economy. Similarly, upgrading the capacity of existing sawmills to supply lumber for mass timber production will result in 34 additional jobs with a total output of $5.63 million.

The potential use of mass timber in mid-to high-rise construction and the associated carbon benefits in the United States.

Nonresidential and mid- to high-rise multifamily residential structures in the United States currently use little wood per unit floor area installed, because earlier building codes lacked provisions for structural wood use in those types of buildings. However, revisions to the International Building Code allow for increased wood use in the form of mass timber, as structural and fire safety concerns have been addressed through new science-based design standards and through newly specified construction materials and measures. This study used multiple models to describe alternative futures for new construction, mass timber adoption rates, and the associated carbon benefits in higher than three-story buildings in the United States. The use of mass timber, in place of traditional constructions (i.e., structures dominated by concrete and steel), in projected new higher than three-story buildings was shown to provide combined carbon benefits (i.e., global warming mitigation benefits), including avoided embodied carbon emissions due to the substitution of non-wood alternatives and additional biogenic carbon storage in mass timber materials, of between 9.9 and 16.5 million t CO2e/yr spanning 50 years, 2020 to 2070. These carbon benefits equate to 12% to 20% of the total U.S. harvested wood products carbon storage for 2020. Future research is needed to understand how greater mass timber adoption leads to changes in forest product markets, land use, and total forest sector carbon.