| 1. |
- Hagentoft, Carl-Eric, 1958, et al.
(författare)
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A conceptual model for how to design for building envelope characteristics. Impact of thermal comfort intervals and thermal mass on commercial buildings in U.S. climates
- 2021
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Ingår i: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 35
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents a simplified conceptual model for energy demand calculations based on building envelope characteristics, thermal mass and local climate. It is based on a network model and lumped analysis of the dynamic process. Characteristic parameters for the buildings are suggested; Driving temperature (DT), Driving temperature difference, (DTD), External Load Temperature (ELT), and Thermal Load Resistance (TLR). The Building Envelope Performance (BEP0), based on a controlled constant indoor temperature is introduced. Solution techniques using stable explicit forward differences based on analytical solutions are derived. The conceptual model has been used for mapping the Driving temperature difference and introduced two performance factors α and β. The first factor represents the effect of thermal comfort interval and thermal mass on the energy demand. The latter represents the ratio between cooling and heating energy demand. These three parameters and factors have been visualized on U.S. maps and enable a possibility to communicate the demand of energy, and cooling and the coupling to building characteristics, in a concise way.
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| 2. |
- Jalilzadehazhari, Elaheh, 1985-, et al.
(författare)
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Subsidies Required For Installing Renewable Energy Supply Systems Considering Variations In Future Climate Conditions
- 2021
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102 .- 2352-7102. ; 35, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Improving the energy performance of detached houses is expected to play an important role in achieving energy and climate targets in Sweden. The majority of detached houses require energy renovations due to technical deteriorations in heating, ventilation, and air conditioning systems approaching the ends of their lives. Renewable energy supply system implementation leads to total energy use reduction. No previous studies provided information regarding how possible climate futures could affect subsidies required to implement these systems. This study compared the performance of an air-to-water heat pump (ASHP), a ground-source heat pump (GSHP), and an integrated system of a ground-source heat pump and photovoltaic solar panels (GSHP-PV) in reducing the total energy use of a detached house, which was initially supplied by an electric boiler. The performances of the supply systems were analysed in regard to three different climate scenarios, following the Special Report of Emissions Scenarios, A2 storyline. The effects of three different interest rates and two different lifetimes on subsidies were also investigated for all three energy supply systems. The GSHP-PV system was the most efficient system, as it secured 97%–100% of the total energy consumption, followed by GSHP and AWHP. The analyses of the results showed that variations in future climate conditions changed the subsidies required to install the supply systems. Furthermore, the results showed that changes in lifetime had greater impact on subsidies than interest rate growth.
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| 3. |
- Johansson, Pernilla, et al.
(författare)
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How well do mould models predict mould growth in buildings, considering the end-user perspective?
- 2021
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Ingår i: Journal of Building Engineering. - : Elsevier Ltd. - 2352-7102. ; 40
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Tidskriftsartikel (refereegranskat)abstract
- Mould growth results from a complex interaction between environmental factors, material properties, and mould fungi characteristics. These interactions must be considered during the design, construction and maintenance of a building to prevent growth. Mould prediction models aim to predict whether mould will grow on a specific material in a part of building with a known, or simulated, relative humidity and temperature. They are often used in the design phase. Several models are available. There is limited research on the performance of the models in real buildings. This study aimed to evaluate six different models, using data from five building parts. The predictions on whether mould growth was expected or not were compared to actual mould growth observations on five building materials. The study was performed as a round-robin. Most models underestimated the possibility for mould when humidity and temperature varied a lot by time. The outcome also depended on the end-user, who needs to make assumptions and parameter values choices on, for example, material susceptibility for mould growth. Therefore, using the same climate data, mould growth prediction may differ depending on who makes the prediction. One model, MOGLI model, where input data comes from laboratory tests and no such assumptions must be made, predicted correct in most cases. One conclusion of the study is that when predictions are made in practice, the results must be used cautiously. More knowledge is needed to understand, and more accurately model, the relationships between the moisture and temperature variations in buildings and the risk for mould growth.
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| 4. |
- Sadrizadeh, Sasan, et al.
(författare)
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A systematic review of operating room ventilation
- 2021
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Ingår i: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 40, s. 102693-
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Forskningsöversikt (refereegranskat)abstract
- Ventilation systems are the primary way of eliminating airborne pathogenic particles in an operating room (OR). However, such systems can be complex due to factors such as different surgical instruments, diverse room sizes, various staff counts, types of clothing used, different surgical types and duration, medications, and patient conditions. OR ventilation should provide a thermally comfortable environment for the surgical staff team members while preventing the patient from suffering from any extreme hypothermia. Many technical, logistical, and ethical implications need to be considered in the early stage of designing a ventilation system for an OR. Years of research and a significant number of publications have highlighted the controversy and disagreement among infection specialists, design engineers, and ventilation experts in this context. This review article aims to provide a good understanding of OR ventilation systems in the context of air quality and infection control from existing research and provide multidimensional insights for appropriate design and operation of the OR. To this end, we have conducted a systematic review of the literature, covering 253 articles in this context. Systematic review and meta-analyses were used to map the evidence and identify research gaps in the existing clinical, practical, and engineering knowledge. The present study is categorized into six research focuses: ventilation system, thermal comfort, staff work practice and obstacles, door operation and passage, air cleaning technology, emission rate, and clothing systems. In the conclusion, we summarize the key limitations of the existing studies and insights for future research direction.
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| 5. |
- Shahreza, Seyedmohammad Kahangi, et al.
(författare)
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Experimental investigation of water absorption and penetration in clay brick masonry under simulated uniform water spray exposure
- 2021
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Ingår i: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 43, s. 102583-102583
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we performed an experimental investigation of water absorption and penetration in clay brick masonry exposed to cyclic water spraying by employing a newly developed test setup. Several parameters, including brick absorption properties and different mortar joint profiles, were investigated. The specimens were exposed to a uniform water spray rate ranging between 1.7 and 3.8 l/m2/h, and water absorption and dampness patches on the non-exposed backside (the protected side) of the specimens monitored continuously. The results indicate that the amount of absorbed water is highly dependent on the water absorption coefficient and absorption capacity of the bricks, whereas the mortar joint profiles do not influence water absorption. The first dampness patches on the specimens' backside appeared in the vicinity of the head joint, and the time until the first patch appeared correlated well with water content levels. Accordingly, the first visible dampness patches appeared on the specimens' backside at water content levels corresponding to 50%–60% of full saturation level. Additionally, the specimens' backside reached 90% dampness at water content levels corresponding to 95% of full saturation level. As a feature attributed to the absence of known defects and zero differential air pressure, no measurable amounts of penetrated water could be collected at the specimens’ backside. The newly developed test setup might facilitate verification of moisture simulations and provide a basis for rational decision-making concerning clay brick masonry design and maintenance.
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| 6. |
- Song, Shoutan, et al.
(författare)
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Experimental study on cyclic response of concrete frames reinforced by Steel-CFRP hybrid reinforcement
- 2021
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 34
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Tidskriftsartikel (refereegranskat)abstract
- A novel section with Steel-carbon fiber reinforced polymer (CFRP) hybrid reinforcement is introduced. CFRP longitudinal reinforcements are placed in the outer layer of the section, while steel reinforcements are arranged in the inner layer. The new type section is utilized to reduce the residual deformation of anti-seismic structures and improve the durability of structures. Cyclic loading tests are conducted on the four concrete frame structure with an axial compression ratio of 0.31. Seismic performances of concrete frames with steel reinforcements, steel-CFRP hybrid reinforcements and CFRP reinforcements are compared and studied. The major objectives of study are focus on the performance of CFRP reinforcements under the axial compression ratio of 0.31 and the ductility, energy dissipation, strength degradation, unloading stiffness, residual deformation of the frame structure with different reinforcement modes. Test results showed that as compared with the steel reinforced concrete frame, Steel-CFRP hybrid reinforced concrete frame exhibited excellent post-earthquake repairabilities, comparable hysteretic energy dissipation abilities and reasonable strength degradation. Furthermore, when the axial compression ratio is 0.31, the ultimate tensile strength of CFRP reinforcements calculated in accordance with the bearing capacity is 27.2%-32% of the static ultimate tensile strength. The concrete frame with ideal mechanical properties can be obtained by reasonable allocation of steel and CFRP reinforcement.
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| 7. |
- Tran, Nghia P., et al.
(författare)
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A critical review on drying shrinkage mitigation strategies in cement-based materials
- 2021
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 38
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Forskningsöversikt (refereegranskat)abstract
- Drying shrinkage deformation due to moisture migration is a major concern in cementitious materials and can lead to a high probability of cracking, resulting in a deterioration in long-term performance and serviceability. In this paper, the primary mechanisms of drying shrinkage, mitigation strategies and the research gaps are elucidated to provide a comprehensive understanding of the factors influencing drying shrinkage and identify research strategies to assist in the development of novel shrinkage-resistant concrete. The use of shrinkage-reducing admixture is identified as the high-efficiency methodology. This reduces the surface tension of the liquid in the capillary pore, resulting in a 20–50% drying shrinkage reduction when applied with a dosage up to 3%. It can achieve even greater efficiency by combining the admixture with expansive agents to provide synergistic effects, giving mitigation of drying shrinkage of up to 80%. Replacing cement with supplementary cementitious materials, up to 35%, is also an effective approach to mitigate drying shrinkage, giving a reduction between 5–42%. The reinforcing effect of novel carbon-nanotubes, albeit at a small dosage (0.1% w.t), can effectively strengthen the C–S–H gel matrix, resulting in a drying shrinkage reduction of 15–21%. Introducing internal restraints using fibres or aggregate also demonstrates high effectiveness for drying shrinkage mitigation. Furthermore, coupled CO2-water curing or coating the concrete surface to prevent moisture loss provides an innovative approach to drying shrinkage reduction at an early age (50–70%). Finally, to avert time-dependent deformation, the use of superplasticizer (less than 1%) based on the polycarboxylate polymer is suggested.
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| 8. |
- Wang, Tianxiang, 1995-, et al.
(författare)
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An innovative timber-steel hybrid beam consisting of glulam mechanically reinforced by means of steel rod : Analytical and preliminary numerical investigations
- 2021
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Ingår i: Journal of Building Engineering. - : Elsevier Ltd. - 2352-7102. ; 43
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Tidskriftsartikel (refereegranskat)abstract
- There is an increasing interest in large-dimensional timber structural elements within the construction sector in order to fulfil the combined demand of sustainability, open spaces and architectural flexibility. Current timber technology allows for efficient production of long-size beams, but many problems are related to their overall high costs due to difficulties in transportation, manufacturing on site and handling during the mounting phase. Hence, the aim of this work is to propose and study an innovative timber-steel hybrid structural element composed of shorter pieces of beams connected and reinforced by means of a system consisting of steel shear keys and steel rods. The small timber elements and steel devices can be prefabricated with low costs and easily assembled into large elements at the construction sites. The proposed system can also be used for retrofitting of existing timber members when it is necessary to increase their strength, stiffness and ductility. The structural behavior of the proposed system was therefore studied both as a connection and as a retrofitting technique, which were analyzed via two types of hybrid beams, one with a splice at mid-span and one without, separately. A simple glulam beam with the same geometrical characteristics of the two hybrid structures was also investigated for the comparison of the structural behavior. The analytical results show that the hybrid beams with and without splice have both obtained significant increasement in the stiffness, strength and ductility. The numerical analyses are limited in the elastic stage due to the elastic mechanical properties assigned to the structural components. The numerical results show good agreement with the analytical ones for each type of beam in terms of the stiffness in the elastic stage. Finally, the influence of the parameters such as the distance between shear keys, slip modulus of shear keys and diameter of rod, on the structural behavior of hybrid beams is discussed in this paper.
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| 9. |
- Yang, Bin, et al.
(författare)
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Influence of relayed fans and low level exhausts on performance of attachment ventilation under heating mode
- 2021
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- Compared with displacement ventilation, attachment ventilation characterized by high supply air momentum has the potential to generate warm air lake on the floor under winter heating mode. However, the airflow can not keep attaching to the floor and moves upwards by thermal buoyancy. The influence of relayed fans and low level exhausts on performance of attachment ventilation under heating mode was explored. One/two relayed fans and five dimensionless exhaust heights were investigated. Performance evaluating index include vertical temperature gradient, temperature efficiency, predicted mean vote (PMV), predicted percentage of dissatisfied (PPD) and Draught risk (DR). Simulation results showed that relayed fans and low level exhausts effectively increase the attachment length of warm air lake in winter. Operation of relayed fans reduces vertical temperature difference, maintaining the head and foot temperature difference less than 3 °C. Low level exhausts effectively increase occupant zone temperature, reduce airflow short circuit and improve temperature efficiency. The operation of relayed fans slightly increase the temperature efficiency under high level exhausts. Two relayed fans decrease the temperature efficiency under low level exhausts. Better performance can be achieved by using only one relayed fan.
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| 10. |
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