Cross-laminated Timber Products Research Articles

Evaluation of bending and shear properties of mixed softwood & hardwood cross-laminated timbers

The current version of PRG-320 Standard for Performance-Rated Cross-Laminated Timber (CLT) that governs CLT manufacturing and design, limits production to softwood species. As a result, the growing demand for CLT production could strain the supply of softwood lumber in the US within the next decade. The inclusion of hardwood in CLT production alongside softwood could be a potential solution to this problem. This paper investigates the bending and shear test results of three- and five-layer mixed species CLT beams manufactured using various combinations of yellow-poplar and southern pine. The beams were evaluated for bending strength, bending stiffness, shear strength, and shear stiffness, as well as quality control testing of moisture content, specific gravity, resistance to shear by compression loading and resistance to delamination. The experimental values for all CLT groups, adjusted according to the Allowable Stress Design (ASD) to ensure stress limits are not exceeded, were greater than those calculated using the shear analogy method. The only exceptions were bending stiffness values for the groups with all layers of southern pine and those with outer layers of southern pine and inner layers of yellow-poplar (see Table 1 for layups codes), where the differences remained within a minor range of 4 %. Although, wood failure percentages in resistance to shear by compression loading fell below the maximum value of 80 %, and face delamination percentages in resistance to delamination were above the minimum value of 5 % according to the corresponding standards. The mechanical properties of all CLT beams met or exceeded shear analogy values. The test results indicated that yellow-poplar could be a viable alternative to southern pine in the production of CLT due to its similar specific gravity. This suggests that mixed-species CLT can maintain or enhance structural performance while addressing material shortages. Furthermore, the use of yellow-poplar in CLT production promotes sustainable forestry practices, supports resource diversification, and encourages innovation in construction methods. These findings have significant practical implications for the timber and construction industries, contributing to cost efficiency and environmental sustainability.

Innovation ecosystems beyond construction projects – a case study of Swedish cross laminated timber building networks

ABSTRACT While innovation ecosystems have been proven effective for driving innovation in high-tech industries, their application in construction with cross laminated timber (CLT) products have received limited attention, with most studies adopting a broad perspective on ecosystems, encompassing the entire supply network around individual building projects. This study explores niche innovation ecosystems within the context of construction with CLT products. Data from 15 CLT-based building projects in mid Sweden were collected through observations and interviews and analysed using a method combining existing theory on innovation ecosystem structure with social network analysis. Innovation ecosystem structure was identified within five of the projects, encompassing two unique ecosystems. These ecosystems feature interorganisational links and actor-level expected value capture in two dimensions: value creation within the standard contractual framework of the projects and the innovation ecosystem superimposed on these projects. The novel method bridges the gap between innovation ecosystem research and CLT practices. The findings reveal that niche innovation ecosystems interact with CLT-based building projects through collaborative efforts across multiple projects and partners. These ecosystems feature alignment links that indicate both intra – and inter-project interdependencies, potentially driving innovation in construction. Role extensions within these ecosystems highlight the complexity and adaptability required in the construction industry.

Gluing parameters optimization and failure mechanism of cross-laminated timber prepared with Chinese fir

Cross-laminated timber (CLT) has become a popular engineered wood product, mainly prepared from imported wood in China. More extensive research is needed to improve the local production of cross-laminated timber with fast-growing coniferous wood species. Chinese fir (Cunninghamia lanceolata) and one component polyurethane (1C-PUR) adhesive were selected to prepare CLT under different process parameters. International standard methods, scanning electron microscopy (SEM), optical microscopy (LM), confocal laser scanning microscopy (CLSM), and nanoindentation (NI) were applied. The bonding performance and failure mechanism of Chinese fir CLT were investigated and clarified. The results showed that the optimal gluing parameters for preparing CLT from Chinese fir wood were 160 g/m2 of glue, 0.9 MPa of pressure, and 180 minutes of pressing time. Failure of CLT made from Chinese fir lumber was mainly due to the shear failure of the vertical layer board. Cracks often appeared in the earlywood cells near the boundary between earlywood and latewood. The impact of adhesive penetration on the mechanical properties of the wood cell wall showed that adhesive penetration increased the elastic modulus of the cell wall at earlywood and latewood cells.

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.

Face bonding strength of cross laminated northern hardwoods and softwoods lumber

Producing cross-laminated timber (CLT) has opened a new market for the lumber industry in North America, while few hardwood species have been studied in the U.S. for CLT production. Combining hardwood species in mixed hardwood CLT or in hybrid CLT can be a solution to boost the market of the undervalued hardwoods. However, the knowledge gap on bonding hardwoods needs to be filled to provide evidence of feasibility. This study focused on the face bonding properties of the cross laminations made of seven hardwood species and two softwood species from the Great Lakes region using two commercial structural adhesives, the phenol resorcinol adhesive (the Resorcinol) and the melamine urea formaldehyde adhesive (the Melamine). A total of 45 combinations of the selected species were studied for the bonding strength (shear under compression) and the percentage of wood failure. For single species samples, the bond strength was positively related to the specific gravity of wood and the bond strength of hardwoods was 33% and 82% stronger than that of softwoods bonded with the Resorcinol and the Melamine respectively. The mixed hardwoods showed higher bonding strength (the Melamine: 5.45 MPa, the Resorcinol: 5.28 MPa) than mixed softwoods (the Melamine: 2.8 MPa and the Resorcinol: 2.7 MPa). Among the Resorcinol bonded mixed combinations, 54% had a percentage of wood failure less than 80%, while the Melamine bonded had only 4 out of 22 which had a percentage of wood failure less than 80%. The overall bonding strength of the hybrid combinations was 5% weaker than that of the mixed hardwoods. All hybrid combinations bonded with the Melamine met the 80% wood failure criterium, but some bonded with the Resorcinol had a percentage of wood failure less than 80%. Anatomical features, especially pore distribution, played a key role in the bonding performance. However, the Melamine adhesive consistently achieved over 80% wood failure across all pore distribution types.

Measurement and analysis mechanical properties of cross-laminated timber (CLT) product: Case study on typical lampung lamina arrangement

Recently, the development of cross-laminated timber (CLT) products that can substitute large-dimensional wood for structures and reduce waste of wood products with small dimensions and pieces continues to be developed, and demand from industries continues to increase. Therefore, this study aims to measure and analyze the mechanical properties of cross-laminated timber (CLT) products designed with a typical arrangement of the Lampung region, Indonesia, called a screen arrangement. Measurement and analysis of mechanical properties include measuring load tests and analyzing moments and stiffness of CLT products intended for floor and beam structures. The screen-type wood arrangement used in the product consists of an inner screen arrangement, an outer screen arrangement, and a standing screen arrangement with polyvinyl acetate adhesive. Load test measurements were carried out using a universal testing machine (UTM) and moment and bending stress analysis using engineering mechanics. Generally, the results show that CLT products with standing screens have smaller mechanical properties than those intended for floors and beams. This research shows that the typical CLT arrangement of the Lampung region (Indonesia), in the form of a screen, has strong mechanical properties and characteristics that can be compared with other arrangements.

Producing Hardwood Cross-Laminated Timber (HCLT) Mats from Low-Grade Red Oak Lumber

Abstract The use of cross-laminated timber (CLT) has significantly grown in North America, but hardwood species have not yet been deemed a viable raw material for manufacturing CLT panels. Therefore, softwood species continue to serve as the only approved material for CLT in structural applications according to ANSI/APA PRG-320. Nonstructural CLT products that utilize low-grade lumber from hardwood species, are a good option for introducing hardwoods into the CLT market. Of the hardwood species located within Appalachia, northern red oak (Quercus rubra) is readily available. The purpose of this research was to develop hardwood cross-laminated timber mats utilizing low-grade red oak lumber. In order to manufacture red oak CLT mats, the best adhesive and bonding parameters had to be identified. Overall, sample CLT panels were made using three adhesives with nine different setups for each adhesive. The sample panels were processed into smaller blocks and separated for cyclic delamination and shear-block tests following the ANSI/APA PRG-320 standards. This research determined that a phenol–resorcinol formaldehyde (PRF) adhesive produced the lowest percentage of delamination, satisfying the delamination requirements. The PRF adhesive also produced the largest percentage of wood failure in shear-block testing, however, the results fell short of meeting the requirements. A Taguchi statistical analysis was used to predict the optimal bonding parameters for each adhesive. The optimized bonding parameters for the polyurethane (PUR) adhesive produced favorable results, indicating the delamination results have the potential to nearly meet the standard requirements, while the predicted shear results would exceed the requirements.

The Bending Properties of Hybrid Cross-Laminated Timber (CLT) Using Various Species Combinations.

Cross-laminated timber (CLT) has become a massive commercial success in recent years due to its high performance, technological advantages, and low environmental impact. The finite softwood raw material supply has motivated researchers to find alternatives. This study presents an investigation of the viability of some Hungarian hardwood materials, such as CLT materials. Homogeneous beech, poplar, and spruce panels, as well as their combinations, were created using a polyurethane adhesive. The experimental results show the clear potential of Hungarian poplar, which performed much better than spruce. Poplar's modulus of elasticity (MOE) and modulus of rupture (MOR) values reached or exceeded those of high-grade commercial softwood CLT. The bending properties of beech and hybrid beech-poplar panels far exceeded the performance of commercial panels, which shows the excellent potential of high-density hardwoods for high-performance CLT production. Beech-spruce hybrid panels seriously underperformed. This was caused by gluing issues, probably due to the large density differences between the two species, as evidenced by the glueline failure exhibited by most of these specimens during testing. The average panel density proved to be the best predictor of mechanical performance, except for beech-spruce hybrid panels.

Producing structural grade hardwood lumber as a raw material for cross-laminated timber: Yield and economic analysis

The economic feasibility of producing structural-grade hardwood lumber (SGHL) that qualifies as a raw material for structurally rated cross-laminated timber (CLT) was examined. 126 yellow poplar logs from diameters 12 to 15 inches were selected and divided into test and control samples. A log yield study was then conducted of the yield and revenue generated when producing lumber graded with National Hardwood Lumber Association (NHLA) rules, SGHL rules, and a mix of both rules (NHLA and SGHL-graded lumber). Producing mix-grade lumber added approximately 27% more revenue than producing NHLA-grade lumber on average if sawmills adopt a cant sawing method. Mix-grade lumber production resulted in 32% of the total volume produced as SGHL and the remaining 68% as NHLA lumber. As a result, 2 Common and lower-grade lumber board footage was reduced to only 29% in test samples and remained converted into SGHL compared to more than 85% of 2 Common and lower-grade lumber boards for control samples. 95% of the SGHL produced as mixed-graded lumber with NHLA-grade lumber met the specifications required to produce structural CLT, and the remaining 5% can be utilized to produce non-structural grade CLTs if they meet the minimum requirement of the materials for CLT production.

Effect of Glue Spread on Bonding Strength, Delamination, and Wood Failure of Jabon Wood-Based Cross-Laminated Timber Using Cold-Setting Melamine-Based Adhesive.

Cross-laminated timber (CLT) has become a popular engineered wood product due to its innovative properties and rapid development, which involves the use of various wood species and adhesives. This study aimed to assess the effect of glue application on the bonding strength, delamination, and wood failure of CLT made from jabon wood and bonded with a cold-setting melamine-based adhesive at three different rates: 250, 280, and 300 g/m2. The adhesive was composed of melamine-formaldehyde (MF) by adding 5% citric acid, 3% polymeric 4,4-methylene diphenyl diisocyanate (pMDI), and 10% wheat flour. Adding these ingredients increased the adhesive viscosity and decreased the gelation time. The CLT samples, made using cold pressing in the melamine-based adhesive at a pressure of 1.0 MPa for 2 h, were evaluated as per the standard EN 16531:2021. The results revealed that a higher glue spread resulted in a greater bonding strength, lower delamination, and a higher wood failure. The glue spread was shown to have a more significant influence on wood failure compared with delamination and the bonding strength. The application of 300 g/m2 glue spread (MF-1) on the jabon CLT led to a product that met the standard requirements. The use of modified MF in cold-setting adhesive produced a potential product that could be a feasible option for future CLT production in terms of its lower heat energy consumption.

Identifying Optimal Locations for Hardwood CLT Plants in Tennessee: Application of a Spatially Explicit Framework

Abstract The prospect of using mass timber products, such as cross-laminated timber (CLT), for building material has increased in recent years because of the advantage of these products over their substitutes in terms of structural rigidity, cost efficiency, and climate benefits. However, the American National Standard developed for CLT currently applies to softwood only. With the expected increase in the market for CLT, the supply chain needs to address the projected rise in demand for hardwood as well. Promoting the production of hardwood mass timber like CLT requires studying the feasibility of quality hardwood lumber supply and identifying the optimal locations for investing capital in CLT manufacturing plants. By presenting a case from Tennessee, this study provides a spatially explicit framework to use a variety of factors such as transportation networks, proximity to sawmills, sawmill capacity, and roundwood supply to identify optimal CLT plant locations. Specifically, fuzzy multicriteria analysis was used to identify potential locations, which provided inputs for a location-allocation model to identify optimal locations for CLT plants. Among the several potential locations, three optimal locations suitable for CLT plants were identified with 12,504 thousand cubic feet (MCF) annual production potential of CLT panels in Tennessee. Although increasing transportation distance for lumber procurement would increase CLT production capacity, it would also result in increased lumber supply costs. Potential investors and regional planners interested in using hardwood forest products can benefit from these findings to locate suitable sites for new investment.

Multivariate Image Analysis Applied to Cross-Laminated Timber: Combined Hyperspectral Near-Infrared and X-ray Computed Tomography

Engineered wood products, such as cross-laminated timber (CLT), are becoming more popular in the designs of modern sustainable buildings. This increased production of CLT requires more robust, yet less labour-intensive means to assess the material characteristics of whole CLT panels. In exploring ways of improving efficiency, this study explores multivariate image analysis (MIA) via partial least squares discriminant analysis (PLS-DA) machine learning as a means to classify CLT material features. CLT panels underwent nondestructive testing using near-infrared (NIR) hyperspectral imaging and X-ray computed tomography (CT) analysis. MIA was performed on these results to build predictive models for wood features, such as fibre alignment and knot type. The models showed that it was possible to classify material features on the surface of CLT using NIR alone; whilst when combined with X-ray data, it enhanced the predictive ability of material features throughout the CLT volume. These first results from such modelling have the potential to help map the chemical and physical material properties of CLT, improving the manufacturing efficiency of the product and allowing greater sustainability of engineered wood products.

Economic Ripple Effects Analysis of Cross-Laminated Timber Manufacturing in Japan

Japan has been actively promoting the various uses of timber to efficiently utilize its plantation forests and contribute to its climate commitments. Cross-laminated timber (CLT), owing to its unique structural characteristics and environmental advantages, has received widespread attention in Japan. Being a high-value-added timber, CLT’s value chain involves various industries, including forestry, timber processing, transportation, construction, and civil engineering. However, the economic impact associated with the increasing production and use of CLT is ambiguous. Targeting CLT manufacturers in Japan, this study evaluated the economic ripple effects of CLT through an input–output analysis, which is a method that is used to evaluate the independent association between different economic sectors and industries. An extended input–output table was established according to the survey of revenue and expenditure data of the largest CLT manufacturers in Japan in 2020. The result was compared with the glued-laminated timber (GLT) scenario at the same final demand value. The results showed that activities not elsewhere classified, timber, logs, road freight transport (except self-transport), and wholesale trade were the top five sectors that had the largest economic impact on CLT manufacturing. Our research has implications for policies and programs to promote the revival of forestry and sustainable development of the timber industry in Japan.

Properties of mixed species/density cross laminated timber made of rubberwood and coconut wood

The utilization of rubberwood (Hevea brasiliensis) and coconut wood (Cocos nucifera L.), the essential economic crops in Thailand and tropical countries, was proposed for manufacturing mixed species/density cross-laminated timber (CLT) for building construction. Six 3-layer CLT configurations, which are composed of either medium-density (600 – 799 kg/m3) rubberwood (MRB) or coconut wood (MCC) or high-density (800 – 999 kg/m3) coconut wood (HCC) laminations, were determined considering the mechanical properties and material costs. The outer layers of the control MCC CLT were replaced with either MRB or HCC to improve its mechanical properties, while either outer or core layers of the control MRB CLT were replaced with HCC to reduce its material cost. The material properties of the three wood types and the six CLT configurations were examined. The densities of the produced CLTs were not affected by the chosen manufacturing parameters showing a strong correlation to the lamination's density. From the bonding performance perspective, the mixed-species approach significantly increased the average wood failure percentage of the control MRB CLT. However, only the control MCC CLT achieved the average wood failure percentage greater than 80%, as required in North America's CLT standard. The compressive strength properties of the CLTs in their major strength directions, σclt, were governed by the outer laminations' parallel-to-grain compressive strength. Unlike softwood CLTs, neglecting the load sharing contribution of the core layer in the σclt estimation resulted in 15% underestimation. Rolling shear strength, τrs, was determined by the core laminations regardless of the CLT layups. MRB achieved the highest τrs followed by HCC and MCC, and all values were significantly larger than the common softwood used in CLT production. The results imply that the mixed species/density approaches can effectively improve the mechanical properties of the coconut wood CLT and reduce the material cost of rubberwood CLT without compromising structural performance.

Life Cycle Regional Economic Impacts of Bridge Repair Using Cross-Laminated Timber Floor Slabs: A Case Study in Akita Prefecture, Japan

Recently, cross-laminated timber (CLT) has attracted attention as a civil engineering material in Japan. In particular, the use of CLT floor slabs for bridge repair is expected to have regional economic impacts throughout their life cycle, but their economic impacts have not been evaluated. In this study, the life cycle regional economic impacts of using non-waterproofed CLT, waterproofed CLT, and reinforced concrete (RC) floor slabs for bridge repair in Akita Prefecture, Japan, were compared. Using past-to-present input–output tables, we quantitatively evaluated the economic impacts over the life cycle of floor slabs by estimating the future input–output tables for construction, maintenance, and disposal. The results showed that the construction and maintenance costs (final demand increase) of CLT floor slabs are higher than those of RC slabs, but the regional economic impact is larger. In addition, the non-waterproofed CLT must be renewed every time it is maintained. Therefore, the demand for CLT production in the prefecture will increase, and the economic impact will be larger than that of the other two floor slabs. This demand for CLT production will not only redound to the benefit of the forestry and wood industry but also the revitalization of regional economies.

Rolling Shear Properties of Cross-Laminated Timber Made from Australian Plantation Eucalyptus nitens under Planar Shear Test

With the increasing availability of fast-growing Eucalyptus plantation logs in Australia in recent years, the timber manufacturing sector has become interested in discovering the opportunities of producing value-added timber products from this resource. Cross-laminated timber (CLT) could be a potential sustainable product recovered from this resource and supply material for commercial buildings. Shear of the inner cross-laminates, known as rolling shear, is one of the governing factors in serviceability and limit state design for this product under out-of-plane loading. This study evaluated the rolling shear (RS) properties of CLT with heterogonous layup configurations using different structural grade Eucalyptus nitens (E. nitens) timber under the planar shear test. Based on the results, Gr and τr values were shown to be significantly correlated with the density of the CLT panel. There was also a positive correlation between the RS modulus and MOR of the CLT panel. The specimens with high MOE in the top and bottom layers indicated the highest τr and Fmax values. This indicated that using high-grade boards in the top and bottom lamellae plays an important role in increasing the RS strength, whereas using them in the cross-layer has a positive contribution in increasing shear modulus. The maximum observed RS strength and modulus ranged from 2.8–3.4 MPa and 54.3–67.9 MPa, respectively, exceeding the RS characteristic values of the resource. The results obtained in this study were comparable to those recommended in European standards for softwood CLT, demonstrating the potential use for eucalypt timber boards in CLT production. This paper provides an important insight into supporting the potential engineering applications of CLT panel products fabricated with eucalypt plantation.

Understanding the Impacts of Plant Capacities and Uncertainties on the Techno-Economic Analysis of Cross-Laminated Timber Production in the Southern U.S.

Understanding the economic feasibility of cross-laminated timber (CLT), an emerging and sustainable alternative to concrete and steel, is critical for the rapid expansion of the mass timber industry. However, previous studies on economic performance of CLT have not fully considered the variations in the feedstock, plant capacities, manufacturing parameters, and capital and operating costs. This study fills this gap by developing a techno-economic analysis of producing CLT panels in the Southern United States. The effects of those variations on minimum selling price (MSP) of CLT panels are explored by Monte Carlo simulation. The results show that, across all the plant capacities from 30,000 to 150,000 m3/year, the MSP ranges from $345 to $609/m3 with a ±6%–9% range caused by the variations in feedstocks, key manufacturing parameters, capital and operating cost. The MSP decreases significantly along the increasing capacities. A sensitivity analysis exhibits that the lumber price, lumber preparing loss, plant capacity, and the installed costs of layering and gluing, finishing, and miscellaneous, are the top driving factors to CLT MSP. Supported by Geographic Information System, this study also studies the transportation cost of delivering CLT to customers under three CLT demanding levels (1%, 5%, 15%). The results show that the transportation cost is 1%–8% of the MSP. Lower demanding level or higher plant capacity can increase the transportation cost due to average longer delivering distance. When considering the delivered cost that sums MSP and transportation cost, larger plant capacity does not necessarily generate lower delivered cost.

American tulipwood (Liriodendron tulipifera L.) as an innovative material in CLT technology

American tulipwood (Liriodendron tulipifera L.) as an innovative material in CLT technology. CLT (cross laminated timber, X-Lam) is one type of engineered wood products. The first idea of CLT was presented in the seventies of the last century. It is manufactured with timber boards placed side by side commonly with 3, 5 and 7 layers glued at 90 degrees to adjacent layer. The CLT production technology was developed for softwood. The main species in CLT production is Norway spruce (Picea abies L.) and less often White fir (Abies alba Mill.). Hardwood is also used more and more for production of CLT, most often, the wood of Silver birch (Betula pendula Roth.), Ash (Fraxinus excelsior L.), poplars (Populus spp.), Locust tree (Robinia pseudoacacia L.). This paper describes the suitability of cheap tulipwood (Liriodendron tulipifera L.) as a raw material for the production of CLT. Examples of the use of this type of panels in construction are also presented. The tulipwood has similar physical characteristics to softwood, for which CLT production technologies were previously developed. This makes it possible to use the technology previously for softwood CLT was developed. In addition, the tulipwood is characterized by aesthetic visual quality (wood surface similar to marble). Thanks to this, CLT boards to make exposed surfaces can be used.

CLT construction without weather protection requires extensive moisture control

This study examines how cross-laminated timber (CLT) constructions, including joints, connections and attachment points, are affected by precipitation during construction. The case studies are based on moisture content measurements and material sampling as well as microbiological analysis during the structure’s construction stage. The study does not include remediation control. The field measurements show microbiological growth in all buildings and almost all floor structures that were investigated. Of a total of 200 measuring points analysed, half had mould growth and around a third had moderate or extensive growth. The moisture content measurements for one of the locations with the largest percentage of elevated or high moisture content was at the top of the floor structure in the bottom gap between timbers in the CLT top layer. This is one example of several materials or construction components where there is limited possibility of dry out. Based on the outcome, it would appear difficult, or impossible, to avoid the appearance of microbial growth during construction with CLT without weather protection. Previous studies indicate that microbiological analysis of CLT is extremely rare in both laboratory and field studies, which implies that there are obvious shortcomings in the scientific work. The fact that mould growth is often invisible needs to be disseminated, especially in practical studies. However, there seems to be a good level of awareness in the literature that theoretical studies often conduct mould growth risk evaluations. There do not appear to be any moisture safety assembly methods or solutions for CLT construction that do not have weather protection or a declaration of the critical moisture conditions for CLT products.

Numerical Analysis on Global Serviceability Behaviours of Tall CLT Buildings to the Eurocodes and UK National Annexes

Cross-laminated timber (CLT) is an innovative engineered timber product and has been widely used for constructing tall timber buildings due to its excellent structural performance and good strength with its multi-layers of boards in both perpendicular directions. However, the global serviceability performance of tall timber buildings constructed from CLT products for the lift core, walls, and floors under wind load is not well known yet, even though it is crucial in a design. In this study, the finite element software SAP2000 is used to numerically simulate the global static and dynamic serviceability behaviours of a 30-storey tall CLT building assumed in Glasgow, Scotland, UK. The maximum horizontal storey displacement due to wind is only 16.6% of the design limit and the maximum global horizontal displacement is only 13.8% of the limit set to the Eurocodes. The first three lowest vibrational frequencies, modes and shapes were obtained, with the fundamental frequency being 19.9% larger than the code-recommended value. Accordingly, the peak acceleration of the building due to wind was determined as per the Eurocodes and ISO standard. The results show that the global serviceability behaviours of the building satisfy the requirements of the Eurocodes and other design standards. Parametric studies on the peak accelerations of the tall CLT building were also conducted by varying the timber material properties and building masses. By increasing the timber grade for CLT members, the generalised building mass and the generalised building stiffness can all be adopted to lower the peak accelerations at the top level of the building, so as to reduce human perceptions of the wind-induced vibrations with respect to the peak acceleration.