| 1. |
- Bayat Pour, Mohsen, et al.
(författare)
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Impact of extruded mortar joints on the hygrothermal performance of brick veneer walls : A probabilistic study
- 2024
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Ingår i: Journal of Building Engineering. - 2352-7102. ; 94
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Tidskriftsartikel (refereegranskat)abstract
- Mortar extrusion during bricklaying, resulting from suboptimal workmanship, may act as a bridge linking clay brick masonry claddings and adjacent layers (e.g., insulation or weather-resistant barriers), thereby, facilitating water penetration into the adjacent layer owing to wind-driven rain (WDR). Despite the significant effect of water penetration on the hygrothermal performance of building envelopes, a consensus regarding the incorporation of WDR-induced water penetration into moisture safety designs and analyses remains lacking. In 2022, Kahangi Shahreza et al. tested two distinct brick types with three diverse mortar joint profiles. Consequently, they proposed a water penetration criterion that can be implemented in hygrothermal analysis of clay brick masonry. The research in this paper combines the results of their study with probabilistic hygrothermal analysis by investigating the influence of extruded mortar on mould growth for a timber frame wall with brick masonry cladding. Two water penetration criteria, including ASHRAE and experimental study (ES) based on Kahangi Shahreza's study, were implemented while considering the different climatic conditions in Sweden. A metamodel, established using the random forests (RF) machine learning algorithm, serves as a tool for mould sensitivity analysis. The results of the probabilistic mould growth analysis revealed a congruence between the ASHRAE and ES criteria for locations with high WDR loads. However, in scenarios involving low WDR loads, the ASHRAE criterion yielded a higher maximum mould index than the ES criterion. In addition, the linear and non-linear mould sensitivity analyses demonstrated a positive correlation between the increase in the extruded mortar depth and elevated maximum mould indices. Nevertheless, the strength of this correlation is subject to alterations based on the WDR loads and selected water penetration criteria.
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| 2. |
- Jonasson, Johannes, et al.
(författare)
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Mitigating footfall-induced vibrations in cross-laminated timber floor-panels by using beech or birch
- 2024
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Ingår i: Journal of Building Engineering. - 2352-7102. ; 86:108751
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Tidskriftsartikel (refereegranskat)abstract
- Long-span floors are particularly sensitive to footfall-induced vibrations, making their analysis and design critical for ensuring occupant comfort. Cross-laminated timber (CLT) panels have high stiffness relative to their self-weight and are commonly made of spruce. Hardwoods such as birch and beech possess higher stiffness and mass density, which can potentially improve the vibrational performance of CLT panels. In this study, the vibrational performance of CLT panels made of beech and birch with different mechanical properties was investigated using finite element (FE) models calibrated via experimental modal analysis (EMA) tests, yielding calibration with less than 1% error in natural frequencies. The study demonstrated that birch or beech laminations, compared with spruce ones, can provide a significant mitigation of vibrational responses, both for broadband (to approximately 40% of the spruce reference level) and footfall-induced vibrations (to approximately 20%–30% of the spruce reference level). It is noteworthy that low quality beech can result in a marked amplification that may nearly double the level of footfall-induced vibrations.
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| 3. |
- Karim, Ali Naman, 1992, et al.
(författare)
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Drying of an aerogel-based coating system in Swedish climates: Field tests and simulations
- 2024
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Ingår i: Journal of Building Engineering. - 2352-7102. ; 84
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Tidskriftsartikel (refereegranskat)abstract
- Aerogel-based coating mortars (ACM-systems) introduce new solutions for energy-retrofit of uninsulated building envelopes, preserving their characteristics while minimizing the material thickness. However, when introducing new solutions, the long-term durability needs to be investigated. The hygrothermal (heat and moisture) performance is one aspect that needs to be secured. The aim of this study is to investigate the hygrothermal performance, with specific focus on moisture drying, of an ACM-system for external applications in Swedish climates. A field test was conducted where an ACM-system with 40 mm of ACM was applied on the exterior of a brick masonry wall partition. The temperature and relative humidity in the wall were monitored for 15 months. Furthermore, numerical hygrothermal simulations were used to predict the early stage drying and long-term performance of the ACM-system in four Swedish climates. The field mea- surements showed that the built-in moisture dried out after approximately 6 months, after which the ACM-system followed the variations in the surrounding climate for the remaining period. The simulations predicted that the early stage drying time ranged from 134 to 336 days, depending on climate and time of application. Furthermore, the elevated relative humidity in the ACM due to rainwater absorption resulted in an average thermal conductivity of up to 9 % above the rated value. Consequently, mitigating water absorption at the exterior is crucial for enhancing the long- term thermal performance in high rain load scenarios.
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| 4. |
- Li, Yongqiang, et al.
(författare)
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Durability study of seawater and sea-sand concrete under the combined effects of carbonation and chloride redistribution
- 2024
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Ingår i: Journal of Building Engineering. - 2352-7102. ; 89
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Tidskriftsartikel (refereegranskat)abstract
- This study presents experimental and numerical investigations to comprehensively assess the impact of carbonation on the durability of chloride-blended seawater and sea-sand concrete. It reveals that carbonation leads to a reduction in pH and results in chloride redistribution along the carbonation depth. The microstructure of concrete after carbonation exhibits increased compaction, reduced porosity, and a refined pore structure. Rebar corrosion in this case is initiated by the excess of chloride ions, as proved by Raman results showing that corrosion product is composed of β-FeOOH. A mathematical model considering several affecting factors was proposed to predict the chloride redistribution in seawater and sea-sand concrete exposed to a carbonation environment, and the numerical results were fitted well with the experimental data. The initiation time for corrosion of the steel rebar is markedly shortened due to the combined effects of carbonation and chloride redistribution. It is verified that the ratio of [Cl−]/[OH−] is a key parameter in predicting corrosion initiation for chloride-blended concrete exposed to carbonation condition. The obtained results are expected to promote the resource utilization of seawater and sea-sand concrete in practical engineering.
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| 5. |
- Liu, Fei, et al.
(författare)
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Evolution of particle size distribution and water content for oily particles in machining workshops
- 2024
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Ingår i: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 84
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Tidskriftsartikel (refereegranskat)abstract
- The oily particles produced by aerosolization of the Metalworking fluids (MWFs) pose a threat to human health. To quantify the transmission of oily particles for developing mitigation strategy, the possible particle volatilization, adhesion and coagulation during air transmission should be determined. Therefore, this study firstly by measured the particle size distributions at and away from the emission source in the laboratory. Then, to further verify the results obtained in the laboratory, the particle size distributions of oily particles in a machining workshop were measured. Meanwhile, to better understand the source characteristic of oily particles, this investigation measured the water content of the oily particles in the machining workshop because such a parameter could affect the removal performance of oily particles by filtration. The results revealed that the particle size distributions of oily particles at different locations were similar regardless of the laboratory measurement or on-site measurement. Thus, the evolution of particle size distribution of oily particles during air transmission could be ignored. Besides, the oily particles in the air had a water content of 22.6 % when the MWFs with a water content of 95 % was used during turning process. Although the oily particles in the air contained a certain amount of water, they were difficult to volatilize. The oily particles in the air might mainly consist of pure oily particles and water-in-oil particles. The results in this study could provide guidance for developing better control strategies of oily particles in machining workshops.
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| 6. |
- Sarvašová Kvietková, M., et al.
(författare)
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The influence of the type of coating on thermally modified wood and the resulting durability of the surface treatment on a facade
- 2024
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 91
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Tidskriftsartikel (refereegranskat)abstract
- Many architects choose wooden façades to clad modern buildings, and Thermowood® is a popular choice for such applications. This study focuses on methods to prolong the “fresh” appearance of Thermowood® façades, specifically Thermo-ash (Fraxinus excelsior L.), Thermo-spruce (Picea abies (L.) Karst.) and Thermo-pine (Pinus silvestris L.). The study involves exposing three groups to natural weathering: one reference untreated group, one group with a thin-layer alkyd coating, and another with a thick-layer acrylate coating. The results indicated that a thick-layer acrylate coating was the most suitable treatment for Thermowood® surfaces, as this coating retained a better appearance and demonstrated superior coating durability. Furthermore, cost-benefit analysis (CBA) suggested a thick-layer acrylate coating proved to be the most suitable and cost-effective choice, based on architects’ desires, to maintain a “fresh/original” appearance.
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| 7. |
- Szeląg, Maciej, et al.
(författare)
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Macro- and microstructural evolution of cement paste modified with MWCNTs under thermal shock conditions
- 2024
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 93
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Tidskriftsartikel (refereegranskat)abstract
- The study investigates the influence of multi-walled carbon nanotubes (MWCNTs) on the macro- and microstructure of cement paste (CP) subjected to thermal shock conditions. CPs with 0–0.3 % MWCNTs content, exposed to a sudden temperature load in a range 50–600 °C, were analyzed in terms of mechanical properties, chemical and phase composition, air pore structure, and microstructure of cement hydration products (Si/Ca, Al/Ca, portlandite, unhydrated part of cement). The research found the optimum MWCNT range to be 0.05–0.1 %, enhancing CP's thermal performance by strengthening cement hydration products and their cohesion, by more the nucleation effect than bridging effect. With the application of MWCNTs, the density of the solid cement phase increased, and the amount of the unhydrated part of cement decreased by up to 21.5 %, at 0.1 % MWCNTs content. Unfortunately, the increase in the MWCNTs content resulted in an increase in the pore volume in the worst case, up to 12.7 %, but it did not negatively affect the strength parameters. The MWCNTs effect caused an increase in tensile strength (fcf) by up to 41.0 % at temperatures above 400 °C, where in the most favorable case improvement in compressive strength reached 16.7 %. The study showed that MWCNTs as an admixture to cement composites is suitable for environments where there is a high variability in terms of thermal loads.
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| 8. |
- Tu, Yongming, et al.
(författare)
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Nanoscale insights into NASH under high-velocity fluids erosion: A molecular dynamics study
- 2024
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 94
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Tidskriftsartikel (refereegranskat)abstract
- The poor durability of geopolymer is a major factor hindering its application, and erosion from high-velocity fluids exacerbates this drawback. This study aimed to characterize the microstructural features of geopolymer under high-velocity fluids erosion and investigate the influence of harmful ions on erosion damage. Models of geopolymer/water solution and geopolymer/NaCl solution were constructed to simulate the erosion of geopolymer by high-velocity fluids. The results indicated that under high-velocity fluids erosion, most of the atoms on the surface of the geopolymer experienced leaching, indicating destruction of the substrate. Additionally, water molecules in solution were able to form hydrogen bonds to the substrate surface, accelerating its degradation. Under NaCl solution erosion, Na ions interacted with the exposed bridging oxygen in the geopolymer, and ion exchange occurred between Na ions and the substrate, making the substrate more unstable and leaching more pronounced. The findings of this study provide nanoscale insights into the erosion resistance of geopolymer that could guide the development of new erosion-resistant materials and methods.
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| 9. |
- Vazquez, Elena, et al.
(författare)
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A review of and taxonomy for elastic kinetic building envelopes
- 2024
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 82
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Forskningsöversikt (refereegranskat)abstract
- Building envelopes are primarily responsible for buildings' energy consumption and environmental performance. Kinetic building shadings have emerged as an alternative for improved environmental performance in the past years, dynamically adjusting to changing outdoor conditions. Elastic kinetic systems rely on the flexible nature of their components to achieve motion and can be used in kinetic building shades. Unlike their rigid counterparts, these mechanisms can reduce the part count in kinetic systems (and, thereby, their mechanical complexity) and potentially adapt to synclastic and anticlastic surfaces. This manuscript reviews elastic kinetic systems used in building envelope design, that is, building envelope systems that rely on materials’ elastic properties to their advantage to achieve motion. The first section of the review includes an overview of biomimetics for kinetic building envelope design drawing parallels between plant kinematics and elastic kinetics in regard to material strategies and actuation. The second section of the review analyzes thirteen case studies regarding the level of development, materials used, and actuation strategies. The study showed that polymer-based composites are mainly used to construct elastic kinetics and that other low-carbon materials could be explored in future research. From the case study analysis, a taxonomy was developed to classify their actuation strategies (manual, pneumatic or mechanical, actuation with smart materials) and elastic mechanisms (linear and surface elements which can be compliant or bistable). An area for future work might consider abstracting actuation mechanisms from fast motile plants to offer insights for combining passive actuators with multi-stable elastic kinetics for fast adaptation in kinetic building envelopes.
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| 10. |
- Wang, Yue, 1996-, et al.
(författare)
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Design of birch plywood as gusset plates in timber-timber uniaxial tension connections : Influence of fastener pattern, face grain orientation, and discussions based on the Whitmore effective width theory
- 2024
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Ingår i: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 86
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Tidskriftsartikel (refereegranskat)abstract
- This study reveals timber-timber composite joints consisting of glulam pieces and birch plywood plates with three different load-to-face grain angles. Utilizing a similar number of fasteners and arranging the fastener array from narrow to wide, uniaxial tension specimens were manufactured with four different fastener patterns. The thickness of birch plywood was intentionally under-designed so that the failure modes for all connections were net tension failure of birch plywood plates. Thereafter, the influence of the fastener pattern and face grain orientation on the load-bearing capacity and stiffness of the investigated composite joints was studied. The load capacity and nominal strength generally increased when the nail patterns varied from narrow to wide. This observation was associated with the Whitmore effective width theory (load spread angle) in steel gusset plate design. Moreover, to derive valid analytical methods to predict the net-tension capacity of birch plywood plates, the classic spread angle model that assumes rectangular stress blocks and the modified spread angle model that considers the summation of stresses from each fastener row were discussed. Both models were adopted to predict the net tension capacity of investigated specimens at 0°. In addition, the stiffness of joints was measured and compared with slip modulus formulas in Eurocode 5. The measured local stiffness values were found to be independent of the fastener pattern and load-face grain angles. The analytical slip modulus assuming the case without predrilling exhibited a satisfactory prediction, while formulas assuming the case with predrilling tend to give overestimations.
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