Search Results (27)

With the aim of reducing the environmental impact of buildings, the appropriate selection of building materials is essential, as a building is a complex system composed of various materials. With this background, a multi-criteria decision-making approach has recently gained traction. This study demonstrated the effect of building material selection on both environmental and economic parameters of a building in the context of Japan. A comparative analysis of five structural frame options was conducted utilizing a reference building model to assess the implication of material choices. The findings indicated that wooden frame options are advantageous in environmental aspects compared to non-wooden frames, provided that sustainable forestry practices and appropriate recycling scenarios are implemented. Conversely, it was found that a Cross Laminated Timber (CLT) frame is the most expensive option. This suggests that a hybrid approach, which combines various frame materials, could yield a more effective solution in terms of both environmental and economic sustainability. In addition, it was highlighted that building envelopes, such as foundation, exterior wall, and roof, should be prioritized to enhance the sustainability of a building from a material perspective. Furthermore, gypsum board, commonly used for sheathing building elements, should be selected with careful consideration of its environmental impact. Full article

Cross-laminated timber (CLT) is gaining popularity as a sustainable alternative to traditional building materials. However, the decline of natural vegetation and the growth of plantation hardwoods has led the researchers to consider alternatives. This study presents a comparative analysis of bending and rolling shear performance of homogenous poplar (Populus nigra L.) CLT and hybrid CLT, with maple (Acer platanoides L.), in the outer layer and poplar in the core, compared to spruce (Picea abies (L.), H. Karst.) CLT. The CLT panels were prepared using one-component polyurethane (1C-PUR) and melamine adhesive (ME). Poplar CLT exhibited equal or better properties than spruce CLT. The outer maple layer in the hybrid CLT enhanced the global bending modulus (E_mg) and bending strength (f_m) by 74% and 37%, respectively, due to its higher modulus of elasticity better shear resistance by reducing the cross-layer stress concentrations and rolling shear failure. Additionally, both the adhesive types and wood species significantly influenced the f_m, E_mg, and rolling shear strength (f_r) independently, while their interaction effect was found to be non-significant. The experimental bending stiffness was higher than the theoretical values. The shear analogy method provided the most accurate results for bending and shear strengths, while bending stiffness was best predicted by the modified gamma method, with minor variations. The finite-element models (FEMs) also produced results with a deviation of only 10%. Full article

The building and construction sector accounts for nearly 40% of global greenhouse gas emissions, with steel-framed buildings being a significant contributor due to high CO₂ emissions during production. To mitigate this issue, integrating Cross-Laminated Timber (CLT) into structural systems has emerged as a sustainable alternative. CLT, known for its carbon sequestration properties, offers an environmentally friendly replacement for reinforced-concrete slabs, particularly when paired with steel structures to enhance material reuse and reduce lifecycle impacts. This study focuses on hybrid systems combining H-shaped steel beams and CLT floor panels connected using high-strength friction bolts. A four-point bending test, simulating a secondary beam, was conducted, demonstrating that the composite effect significantly enhances flexural stiffness and strength. Additionally, a simplified method for evaluating the flexural stiffness and yielding strength of these composite beams, based on material and joint properties, was shown to successfully evaluate the test results. Full article

Massive construction systems have always characterized traditional architecture and are currently the most prevalent, straightforward, and cost-effective in many Mediterranean countries. However, in recent years, the construction industry has gradually shifted towards using lightweight, dry construction techniques. This study aims to assess the effects on energy consumption, comfort levels, and environmental sustainability resulting from the adoption of five high-performance construction systems in a multi-family residential building: (i) reinforced concrete structure with low-transmittance thermal block infill; (ii) reinforced concrete structure with light-clay bricks and outer thermal insulation; (iii) steel frame; (iv) cross-laminated timber (CLT); (v) timber-steel hybrid structure. To achieve this goal, a multidisciplinary approach was employed, including the analysis of thermal parameters, the evaluation of indoor comfort through the adaptive model and Fanger’s PMV, and the quantification of environmental and economic impacts through life cycle assessment and life cycle cost applied in a long-term analysis (ranging from 30 to 100 years). The results highlight that heavyweight construction systems are the most effective in terms of comfort, cost, and long-term environmental impact (100 years), while lightweight construction systems generally have higher construction costs, provide lower short-term environmental impacts (30 years), and offer intermediate comfort depending on the thermal mass. Full article

Timber–concrete hybrid structures are commonly employed in multi-story timber buildings; however, further research is necessary to fully understand the seismic performance of these structures as well as the dynamic properties of the floor. The two dynamic concerns, seismic effects and the vibration of floors in hybrid structures, are key issues, in view of which this study aimed to investigate the small-seismic-response spectra and elastic time histories in a high-rise timber hybrid building, specifically the medical technology building of Jiangsu Provincial Rehabilitation Hospital in China. The dynamic characteristics of a localized cross-laminated timber (CLT) floor were tested in situ, and the impacts of human-induced vibration were quantified. Comprehensive theoretical analysis results reveal that the basic vibration pattern of the structure was mainly translational in nature and that the period ratio, inter-story displacement angle, and shear-to-weight ratio all met the demands of the Chinese timber building design code. The experimental test results show that the vertical natural frequency of the CLT floor was about 15.96 Hz and thus met appropriate requirements with respect to natural frequency. However, peak floor acceleration was found to be high under the conditions of a single person walking quickly, a single person trotting, and multiple persons walking randomly. In light of these findings, the floor should be paved with a fine-grained concrete building surface, according to design requirements, so that its serviceability might be improved. Overall, the relevant analytical methods presented in this paper provide guidance and practical reference for the seismic analysis of timber hybrid structures, as well as vibration serviceability analysis for CLT floors. Full article

As the era of sixth-generation (6G) communications approaches, there will be an unprecedented increase in the number of wireless internet-connected devices and a sharp rise in mobile data traffic. Faced with the scarcity of spectrum resources in traditional communication networks and challenges such as rapidly establishing communications after disasters, this study leverages unmanned aerial vehicles (UAVs) to promote an integrated multi-hop communication system combining free-space optical (FSO) communication, terahertz (THz) technology, and intelligent reflecting surface (IRS). This innovative amalgamation capitalizes on the flexibility of UAVs, the deployability of IRS, and the complementary strengths of FSO and THz communications. We have developed a comprehensive channel model that includes the effects of atmospheric turbulence, attenuation, pointing errors, and angle-of-arrival (AOA) fluctuations. Furthermore, we have derived probability density functions (PDFs) and cumulative distribution functions (CDFs) for various switching techniques. Employing advanced methods such as Gaussian–Laguerre quadrature and the central limit theorem (CLT), we have calculated key performance indicators including the average outage probability, bit error rate (BER), and channel capacity. The numerical results demonstrate that IRS significantly enhances the performance of the UAV-based hybrid FSO/THz system. The research indicates that optimizing the number of IRS elements can substantially increase throughput and reliability while minimizing switching costs. Additionally, the multi-hop approach specifically addresses the line-of-sight (LoS) dependency limitations inherent in FSO and THz systems by utilizing UAVs as dynamic relay points. This strategy effectively bridges longer distances, overcoming physical and atmospheric obstacles, and ensures stable communication links even under adverse conditions. This study underscores that the enhanced multi-hop FSO/THz link is highly effective for emergency communications after disasters, addressing the challenge of scarce spectrum resources. By strategically deploying UAVs as relay points in a multi-hop configuration, the system achieves greater flexibility and resilience, making it highly suitable for critical communication scenarios where traditional networks might fail. Full article

Information that is complicated and ambiguous entails high cognitive load. Trying to understand such information can involve a lot of cognitive effort. An alternative to expending a lot of cognitive effort is to engage in motivated cognition, which can involve selective attention to new information that matches existing beliefs. In accordance with principles of least action related to management of cognitive effort, another alternative is to give up trying to understand new information with high cognitive load. In either case, high cognitive load can limit potential for understanding of new information and learning from new information. Cognitive Load Theory (CLT) provides a framework for relating the characteristics of information to human cognitive load. Although CLT has been developed through more than three decades of scientific research, it has not been applied comprehensively to improve the explainability, transparency, interpretability, and shared interpretability (ETISI) of machine learning models and their outputs. Here, in order to illustrate the broad relevance of CLT to ETISI, it is applied to analyze a type of hybrid machine learning called Algebraic Machine Learning (AML). This is the example because AML has characteristics that offer high potential for ETISI. However, application of CLT reveals potential for high cognitive load that can limit ETISI even when AML is used in conjunction with decision trees. Following the AML example, the general relevance of CLT to machine learning ETISI is discussed with the examples of SHapley Additive exPlanations (SHAP), Local Interpretable Model-Agnostic Explanations (LIME), and the Contextual Importance and Utility (CIU) method. Overall, it is argued in this Perspective paper that CLT can provide science-based design principles that can contribute to improving the ETISI of all types of machine learning. Full article

Softwood is widely employed in construction and faces high demand. Australia is grappling with substantial timber scarcity, specifically related to radiata pine, which is the dominant structural timber in the construction sector. However, Australia has a significant hardwood population, which can be utilized to reduce the high demand for radiata pine. This paper aims to investigate the bond properties of both Australian softwood (radiata pine) and hardwood (shining gum). It also discusses the potential to combine softwood and hardwood in glue or cross-laminated timber by evaluating the bond properties of the radiata pine–shining gum interface. For hardwood, the effect of primer is also investigated to determine its efficacy in improving failure mode, bond strength, and stiffness. Lastly, both glulam and cross-laminated timber bonding scenarios are simulated for bond testing by examining the effect of relative fibre orientation on the bond properties of the aforementioned species individually and in combination. Instead of conventional block shear testing, which is predominantly used for same-species bond testing, push-out testing is adopted in this study. However, a comparison with block shear testing is also made in this article. The results indicated that the use of primer on hardwood reduced the inconsistencies in the bond properties and improved wood-side failure rates. It was also concluded that the effect of fibre orientation in a CLT scenario with combined hardwood and softwood failure modes can vary significantly, which leads to a higher standard deviation in the results. Nevertheless, this study outlines the challenges and opportunities for producing hardwood–softwood hybrid glue or cross-laminated timber. Full article

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. Full article

In this study, the vibration serviceability of multi-storey timber buildings is addressed. The core of this study pertains to the preparation of a comprehensive finite element model to predict modal properties for an accurate vibration serviceability checking. To that end, findings obtained from studying three multi-storey timber buildings are summarized and discussed. Two of the buildings (of seven and eight storeys) consist entirely of cross-laminated timber (CLT), while the third is a five-storey hybrid CLT-concrete building. Thanks to the detailed finite element models and modal testing results, one has the capability to conduct sensitivity analyses, classical and Bayesian model updating, and uncertainty quantifications. With these methodologies, influential modelling parameters as well as the sources of modelling error were identified. This allowed for conclusions to be drawn about the in-plane shear stiffness of the constructed walls (whose higher value causes the natural frequencies to increase by up to 25%), the soil deformability (which may cause the natural frequencies to drop by up to 20%), and the perpendicular-to-the-grain deformation of floor slabs (which may lead to an overestimation of a fundamental frequency by up to 8%). Full article

Given that CLT is a relatively recent innovation, there is a notable scarcity of market research in Finland. Presently, there is a limited body of literature that provides a thorough comprehension of the present state, varied applications, and anticipated future developments concerning the use of CLT within the Finnish construction sector. The limited availability of research data underscores the need for more extensive studies to fill this knowledge gap and provide a more nuanced insight into the evolving landscape of CLT adoption within the Finnish construction industry. This article aims to fill this gap through semi-structured, in-depth interviews with 15 Finnish experts. Key findings highlighted that (1) the hierarchical order of familiarity with CLT among construction professionals in Finland, ranging from highest to lowest, was identified as follows: architects, engineers, developers, builders, and contractors; (2) a pronounced necessity exists for heightened expertise and training within the realm of CLT; (3) CLT was considered a promising option in endeavors aimed at mitigating the impacts of climate crises; (4) CLT showcased adaptability to environments marked by highly fluctuating climatic conditions, emphasizing the importance of a comprehensive approach, including proactive maintenance strategies; (5) Finland adopted commendable and forward-looking sustainable practices in forest management; (6) the adaptability of CLT across a wide range of building categories; (7) the perceived vulnerabilities in CLT construction primarily included a lack of cost-competitiveness, insufficient sound insulation, and inadequate production volume; and (8) key future market prospects encompassed the versatility of CLT, increasing demand propelled by environmental considerations, and collaborative advancements in hybrid construction techniques. This article will contribute to the greater usage of CLT in the building industry in Finland by revealing the challenges, potential, and future outlook of CLT use. Full article

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. Full article

The evolution toward small-diameter and fast-growing plantation timbers such as the Pinus elliotti var. elliottii (Engelm) × Pinus caribaea var. hondurensis (Sénéclauze) (PEE×PCH) hybrids around the world is producing large volumes of core wood that are falling short of structural sawn timber grading requirements. Engineered timber products such as cross-laminated timber (CLT) and glue-laminated (glulam) offer potential solutions to value-adding this resource, but the bond performance of this feedstock and the extent to which current standards and guides address its common characteristics for bond performance need to be understood. This study investigated the bond quality and performance of clear defect-free, low stiffness out-of-grade PEE×PCH and evaluated this performance using the pass/fail criteria of the CLT bond performance requirements of three national CLT standards. 5-layer CLT delamination samples and shear block test samples were glued using one-component polyurethane (PUR). This process was repeated for common occurring characteristics in this resource of resin, knots, and pith to understand their impact and inform an evaluation on the need to restrict their inclusion. Clear samples had an average glue line delamination of 2.9% and an average glue line wood failure of 96.7%. Resin achieved 9.3% and 92.6%, respectively. While knots had the lowest performance at 24.4% and 77.4%, respectively. When pith was at or adjacent to the glue line, wood failure occurred through the pith and its immediate surrounding fiber. Shear strength and wood failure tests were carried out on glulam and CLT-oriented samples. CLT knot samples were tested in two load orientations. Glulam-oriented samples in clear, resin, pith, and knots achieved an average shear strength of 8.5 MPa, 8.2 MPa, 7.9 MPa, and 8.2 MPa, respectively, and wood failure of 86%, 85%, 90%, and 69%, respectively. CLT-oriented samples in clear and resin both achieved average shear strengths of 4.0 MPa; 0°-loaded and 90°-loaded pith samples achieved 3.6 MPa and 2.4 MPa, while 0°-loaded and 90°-loaded knot samples achieved 4.2 MPa and 4.7 MPa respectively. Average wood failures were 90%, 89%, 96%, 96%, 83%, and 51%, respectively. PRG320 was found to be the most restrictive standard. Resin, knots, and pith were not addressed in the evaluation of delamination or shear strength in any standard, and PRG320 was the only standard to restrict these characteristics over and above structural grading rules. The amount and type of characteristics present vary considerably in structurally graded wood, and even more so for this out-of-grade resource. It was determined that the negative impact that resin, knots, and pith have on bond quality and bond performance calls for some restriction of their inclusion in order to achieve the author’s interpretation of the intended bond performance requirements of the CLT standards, which currently do not address these characteristics well or at all. A proposed modification to the PRG320 effective bond area was presented as a proactive solution. Full article

Floor vibration, although not a safety concern, is a prevalent performance complaint in multi-story structures. With the increasing use of mass timber construction, various types of long-span timber floors (LSTFs), including plain cross-laminated timber (CLT), CLT with secondary beams (ribbed-deck), and hybrid systems such as timber–concrete composite (TCC) and CLT on-steel-support beams, are gaining popularity. However, due to limited knowledge regarding their vibration characteristics and acceptance criteria, these construction types are often overlooked during the design stage by architects, engineers, and builders. Existing standards and guidelines primarily calibrated for steel and concrete floors lack a validated and calibrated method for evaluating the vibration performance of LSTFs. Nonetheless, it is essential for structural engineers to address vibration concerns during the design stage and potentially investigate excessive vibration in existing buildings, providing mitigation solutions. This article provides a comprehensive overview, discussion, and analysis of the measurement, analysis, design, perception, and acceptability of vibration of timber floors as outlined in international standards and commonly used guidelines. Experimental and theoretical case studies, including vibration measurements of a CLT floor and a comparison of vibration acceptability in lightweight timber floors using different methods, are reported. The results highlight discrepancies between simplified equation calculations and modal analysis observations, underscoring the limitations of relying solely on simplified equations. Furthermore, it is observed that current modal superposition methods tend to be conservative in predicting floor acceleration and velocity responses. Recommendations are provided for future research in the field to enhance floor vibration assessment techniques, aiming for improved design optimization and occupant comfort. Full article

Metaheuristic algorithms have been hybridized with the standard K-means to address the latter’s challenges in finding a solution to automatic clustering problems. However, the distance calculations required in the standard K-means phase of the hybrid clustering algorithms increase as the number of clusters increases, and the associated computational cost rises in proportion to the dataset dimensionality. The use of the standard K-means algorithm in the metaheuristic-based K-means hybrid algorithm for the automatic clustering of high-dimensional real-world datasets poses a great challenge to the clustering performance of the resultant hybrid algorithms in terms of computational cost. Reducing the computation time required in the K-means phase of the hybrid algorithm for the automatic clustering of high-dimensional datasets will inevitably reduce the algorithm’s complexity. In this paper, a preprocessing phase is introduced into the K-means phase of an improved firefly-based K-means hybrid algorithm using the concept of the central limit theorem to partition the high-dimensional dataset into subgroups of randomly formed subsets on which the K-means algorithm is applied to obtain representative cluster centers for the final clustering procedure. The enhanced firefly algorithm (FA) is hybridized with the CLT-based K-means algorithm to automatically determine the optimum number of cluster centroids and generate corresponding optimum initial cluster centroids for the K-means algorithm to achieve optimal global convergence. Twenty high-dimensional datasets from the UCI machine learning repository are used to investigate the performance of the proposed algorithm. The empirical results indicate that the hybrid FA-K-means clustering method demonstrates statistically significant superiority in the employed performance measures and reducing computation time cost for clustering high-dimensional dataset problems, compared to other advanced hybrid search variants. Full article