| 1. |
- Aloisio, Angelo, et al.
(författare)
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Vibration issues in timber structures : A state-of-the-art review
- 2023
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Ingår i: Journal of Building Engineering. - 2352-7102. ; 76
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Forskningsöversikt (refereegranskat)abstract
- The increasing use of timber structures worldwide has brought attention to the challenges posed by their lightweight nature, making them more prone to vibrations than more massive structures. Consequently, significant research efforts have been dedicated to understanding and mitigating vibrations in timber structures, while scientific committees strive to establish suitable design regulations. This study aims to classify and identify the main research themes related to timber structure vibrations and highlight future research needs and directions. A bibliometric-based selection process briefly introduces each research topic, presenting the latest findings and proposals for vibration design in timber structures. The paper emphasizes the key outcomes and significant contributions to understanding and addressing vibration issues in timber structures. These findings serve as valuable guidance for researchers, designers, and regulatory bodies involved in designing and assessing timber structures subjected to vibrations.
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| 2. |
- Alyaseen, Ahmad, et al.
(författare)
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High-performance self-compacting concrete with recycled coarse aggregate : Soft-computing analysis of compressive strength
- 2023
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Ingår i: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 77
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Tidskriftsartikel (refereegranskat)abstract
- The growth of cities and industrialization has led to an increase in demand for concrete, resulting in resource depletion and environmental issues. Sustainable alternatives such as using recycled concrete aggregate (RCA) and industrial waste have been proposed to meet construction material demands while adhering to building codes and promoting sustainability. However, compressive strength (CS) is a crucial property of concrete, and the design parameters have different effects on CS for various grades. Recently, researchers have focused on partially replacing natural coarse aggregate (NCA) with RCA in concrete to achieve sustainability goals. This study aims to examine the influence of design parameters (w/c: water-cement ratio, w/b: water-binder ratio, A/c: total aggregate-cement ratio, FA/CA: fine-coarse aggregate ratio, SP: superplasticizer, w/s: water-solid ratio and RCA%) on concrete CS and address controversies in the insights gained from pairwise comparisons using Pearson's correlation coefficient (PCC) analysis. Additionally, five techniques (M5P, RF, SVM, LR, and ANNs) were used to predict the CS of high-performance self-compacting concrete (HP-SCC) with RCA, and the results were compared with an ANNs-based model as was the commonly used one in literature. The approaches were assessed based on their accuracy measured using correlation coefficient (CC), mean absolute error (MAE), Root Mean Square Error (RMSE), Mean absolute percentage error (MAPE), Scatter index (SI), and comprehensive measure (COM) indicators. Accordingly, the analysis indicated that SVM-PUK-based model is the most appropriate and effective technique to predict the CS of HP-SCC for the given datasets, with CC = 0.894, 0.900, MAE = 1.721, 3.813, RMSE = 5.137, 6.306, and MAPE = 4.5%, 7.6% for the training and testing stages, respectively. The uncertainty analysis results were 21%, 20.7%, 19%, 22%, and 19% for M5P, RF, SVM, LR, and ANN-based models, respectively, whereby all of them were under threshold of 35%. Moreover, according to sensitivity analysis, w/c, w/b, and w/s variables influences the most on CS prediction, while the RCA(%) variable has the least impact.
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| 3. |
- Gamil, Yaser, et al.
(författare)
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Experimental based assessment of formwork pressure theoretical design models for self-compacting concrete
- 2023
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Ingår i: Journal of Building Engineering. - : Elsevier Ltd. - 2352-7102. ; 68
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Tidskriftsartikel (refereegranskat)abstract
- Self-Compacting Concrete (SCC) offers favourable properties which help accelerate the casting time, especially in congested reinforced structures but when casting with SCC uncertainty remains a challenge on the behaviour of its formwork pressure. Researchers have introduced several design models to predict pressure and its behaviour. This research aims to assess the design models that have been reported in the literature. The assessment was carried out through a series of rigorous laboratory tests and the results from the tests served as input for the mathematical model evaluation. Twelve concrete columns with 2 m height were cast in the laboratory to study the effect of varying the input parameters in the existing design models. The formwork pressure was documented by a pressure monitoring system, with the capacity to produce instant results for real-time remote monitoring of the pressure development during and after concrete casting. The formwork pressures were calculated according to the current design models and were compared with pressure data acquitted from the laboratory tests. The results showed that the pressure predicted by the design models was typically greater than the pressure observed during the laboratory tests. The DIN18218 design model showed a relatively close approximation of the pressure distribution over the formwork height and casting time. The limitation of the models is observed when the casting rate varies, and models are sensitive to the input parameters. Thus, additional development of the current design models is needed to enable reliable estimations of the pressure, for example, in the case of low and high casting rates. The laboratory tests also showed that high casting rates and high slump flows generate higher pressures whereas higher thixotropy results in faster pressure reduction during construction.
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| 4. |
- Homod, Raad Z., et al.
(författare)
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Deep clustering of cooperative multi-agent reinforcement learning to optimize multi chiller HVAC systems for smart buildings energy management
- 2023
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 65
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Tidskriftsartikel (refereegranskat)abstract
- Chillers are responsible for almost half of the total energy demand in buildings. Hence, the obligation of control systems of multi-chiller due to changes indoor environments is one of the most significant parts of a smart building. Such a controller is described as a nonlinear and multi-objective algorithm, and its fabrication is crucial to achieving the optimal balance between indoor thermal comfort and running a minimum number of chillers. This work proposes deep clustering of cooperative multi-agent reinforcement learning (DCCMARL) as well-suited to such system control, which supports centralized control by learning of agents. In MARL, since the learning of agents is based on discrete sets of actions and stats, this drawback significantly affects the model of agents for representing their actions with efficient performance. This drawback becomes considerably worse when increasing the number of agents, due to the increased complexity of solving MARL, which makes modeling policy very challenging. Therefore, the DCCMARL of multi-objective reinforcement learning is leveraging powerful frameworks of a hybrid clustering algorithm to deal with complexity and uncertainty, which is a critical factor that influences to the achievement of high levels of a performance action. The results showed that the ability of agents to manipulate the behavior of the smart building could improve indoor thermal conditions, as well as save energy up to 44.5% compared to conventional methods. It seems reasonable to conclude that agents' performance is influenced by what type of model structure.
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| 5. |
- Lidelöw, Sofia, et al.
(författare)
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The promise of BIM? Searching for realized benefits in the Nordic architecture, engineering, construction, and operation industries
- 2023
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 76
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Tidskriftsartikel (refereegranskat)abstract
- Benefits of BIM are not being achieved as expected in the mainstream architecture, engineering, construction, and operation (AECO) industries. Here, we aim to contrast expected and realized BIM benefits in AECO companies and discuss explanations for why benefits proposed in literature have, or have not, been realized. A qualitative research approach is applied to collect and analyse interview data from 47 companies in Finland, Norway and Sweden. Findings show that realized benefits typically occur “within the current practice” of individual organizations' project-related work. In contrast, expected but not realized benefits are long-term, lifecycle oriented and challenge current business and practice. Our proposed explanations acknowledge that fully realizing the expected benefits of BIM suggested in the technology-driven research is restrained by the current sector state-of-practice and assumes a high degree of BIM maturity among all cooperating companies. Thus, we discuss how explanations relate to the fundamental change required to radically leverage the benefits of BIM, challenging both current ways of work and the ubiquitous assumption of clients as drivers for BIM implementation in the sector. Based on our research, we argue that client demand is insufficient to realize the promise of BIM. Suggested research implications include a need for greater supply-driven logic among suppliers of BIM expert services, and the integration of multi-disciplinary competencies within and beyond the traditional disciplines. The research demonstrates the gap between state-of-the-art BIM predicted in literature and mainstream industry's adoption and highlights the importance of extending BIM research to better account for socio-organizational and process aspects of benefits and adoption.
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| 6. |
- Liu, Zhan, et al.
(författare)
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Experimental test on the performance of a −80 °C cascade refrigeration unit using refrigerants R290-R170 for COVID-19 vaccines storage
- 2023
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Ingår i: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 63
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Tidskriftsartikel (refereegranskat)abstract
- With the urgent demand for ultralow-temperature refrigerators worldwide, the operation reliability and stability of the refrigeration system becomes greatly crucial. In this study, a -80 oC ultralow-temperature cascade refrigeration system (CRS) is developed. From aspects of global warming potential (GWP) and ozone depletion potential (ODP), the environmentally friendly refrigerants R290 and R170 are utilized in the high-temperature cycle and low-temperature cycle of CRS. The experimental measurement is conducted in a Type-laboratory with a dry bulb temperature of 25.0 °C and a wet bulb temperature of 20.2 °C. The pull-down and stable operation performance of the CRS freezer are experimentally investigated. Both the inlet and outlet temperature and pressure of two compressors are monitored, and the operation characteristic of the CRS is analyzed. With some temperature test points arranged in the freezer, the temperature drop and temperature fluctuation variation of air are assessed. The operation power consumption of the CRS is also measured during the whole process. It shows that the −80 °C temperature can be generated and realized by the developed ultralow-temperature freezer.
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| 7. |
- Lu, Chujie, et al.
(författare)
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A hybrid ensemble learning framework for zero-energy potential prediction of photovoltaic direct-driven air conditioners
- 2023
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 64
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Tidskriftsartikel (refereegranskat)abstract
- Integrating renewable energy is a promising solution for buildings to achieve the net-zero-energy goal. Expanding real-time matching between renewable energy generation and building energy demand can help realize more enormous zero-energy potential in practice. However, there are few studies to investigate the real-time energy matching in renewable energy building design. Therefore, in this study, a hybrid ensemble learning framework is proposed for analyzing and predicting zero-energy potential in the real-time matching of photovoltaic direct-driven air conditioner (PVAC) systems. First, the datasets of zero-energy probability (ZEP) are generated under the three main climate regions in China, which are with consideration of the load flexibility of air conditioners and based on six important design variables. Second, a novel ensemble learning method named Extreme Gradient Boosting (XGBoost) is selected to predict ZEP and the Bayesian Optimization (BO) is adopted to identify the optimal hyperparameters and further improve the prediction performance. The statistical analysis shows that ZEP distributions are very different from one region to another one and the PVAC systems in Beijing are the easiest to achieve the zero-energy goal. Among all the variables, PV capacity is the most significant and positively related to ZEP. The prediction results show BO-XGBoost achieves more than 99% accuracy and outperforms other benchmark models in the ZEP prediction of three cities. In a word, this paper reveals BO-XGBoost is the most effective model for ZEP prediction and provides the framework for designers to utilize zero-energy potential analysis and prediction for the first time.
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| 8. |
- Rajczakowska, Magdalena, et al.
(författare)
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Autogenous self-healing of thermally damaged cement paste with carbon nanomaterials subjected to different environmental stimulators
- 2023
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Ingår i: Journal of Building Engineering. - : Elsevier Ltd. - 2352-7102. ; 72
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Tidskriftsartikel (refereegranskat)abstract
- Autogenous self-healing of post-fire damaged concrete enables structure performance auto-recovery leading to reduced repair costs, less generated waste, and lower CO2 emissions. In this paper, to improve the efficiency of this process and understand the underlying mechanism, the self-healing of 0.1 wt% MWCNT-modified and pure cement paste subjected to novel environmental stimulators was tested. High-temperature damage was induced at 200 °C and 400 °C, followed by a self-healing cyclic treatment with water, a mixture of water with phosphate-based retarding admixture, and limewater. The self-healing efficiency of the proposed solutions were compared based on crack closure, strength regains, porosity, and chemical composition changes. The surface crack closure after 200 °C varied between 33% and 60%, whereas for 400 °C, only retarding admixture exposure obtained over 50% crack closure and the most considerable decrease in average crack width of 33% for MWCNT-modified paste. The highest values of compressive strength recovery, equal to 18% and 14%, exceeding the intact specimen's compressive strength, were observed for the MWCNT-modified paste healed in water and limewater. Water exposure with an extended wetting phase enhanced the compressive strength recovery of the MWCNT-modified materials. Strong (r = 0.87) and moderate (r = 0.52) positive correlations were observed between temperature loading and compressive and flexural strength recovery parameters, respectively. Higher porosity and interconnected crack network, caused by high temperature, facilitated the self-healing process. Porosity changes before and after healing were pronounced in contrast to the amount of unhydrated cement, which did not exhibit noticeable changes. The healing mechanism included three processes: calcite formation, further hydration inside the cracks, and rehydration of the bulk cement paste.Previous article in issue
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| 9. |
- Trask, Catherine M., et al.
(författare)
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Digital technologies in construction : A systematic mapping review of evidence for improved occupational health and safety
- 2023
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Ingår i: Journal of Building Engineering. - : Elsevier Ltd. - 2352-7102. ; 80
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Forskningsöversikt (refereegranskat)abstract
- There is accelerating development of digital Occupational Health and Safety (OHS) interventions in construction, but it is not clear whether they reduce the risk of injury and illness. This systematic mapping review summarized the state of the evidence and developed recommendations for practitioners and researchers. During a keyword search of scientific databases, 392 unique records were identified and 24 (∼6%) were included in the review. The review was conducted within an Evidence Maturity framework developed for public health interventions, which outlines criteria for intervention. Studies are characterized by innovative application of a wide variety of technologies throughout pre-construction planning, construction execution, and worker training. Targeted hazards primarily included falls, struck-by incidents, and location-based hazards. Most studies focused on technology development and provided low to no evidence of improved work conditions or reduced injury/illness among construction workers. More evidence is needed before the digital solutions are promoted for widespread use. In order to achieve this, more attention need to be paid on the conflicting logics between the evidence maturity framework and the project logic in the construction practice.
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| 10. |
- Wang, Yue, 1996-, et al.
(författare)
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Birch plywood as gusset plates in glulam frame via mechanical connectors : A combined experimental and numerical study
- 2023
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Ingår i: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 65, s. 105744-
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Tidskriftsartikel (refereegranskat)abstract
- Birch is a short-lived hardwood species widespread in the Northern Hemisphere. Plywood made from birch has superior mechanical properties compared with that made from most softwoods, which makes it suitable for structural application. In this study, the feasibility of using birch plywood as gusset plates in timber-timber connections is presented. Test frames consisting of birch plywood gussets and glulam beams connected by nails were built and tested. A 2D analytical model based on truss theory and a 3D finite element model were proposed and constructed. Both models showed satisfactory agreements with the test results in terms of stiffness and strength. Tensile failure on the birch plywood gussets along the outermost row of nail holes was observed in the experiment. The observed failure modes and the stress distributions in the 3D numerical model suggest that the spreading angle (Whitmore effective width) theory should be considered in the design phase of birch plywood gusset plates. Besides, a modified spreading angle theory is proposed to both approximate the stress distribution and predict the load-bearing capacity.
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