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Sustainable Building Retrofit and Energy Optimization

A special issue of Sustainability (ISSN 2071-1050). This special issue belongs to the section "Sustainable Engineering and Science".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 42242

Special Issue Editors

Department of Engineering, Università degli Studi del Sannio, Piazza Roma 21, 82100 Benevento, Italy
Interests: thermodynamics; modeling of energy systems; energy optimization; energy efficiency; building performance simulation; building optimization; energy retrofit; sustainable design; cost-optimal analysis; energy policies
Special Issues, Collections and Topics in MDPI journals
Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
Interests: modeling of energy systems; energy optimization; energy efficiency; building performance simulation; building performance optimization; energy retrofit; sustainable design; cost-optimal analysis; HVAC systems; renewable energy source systems

Special Issue Information

Dear Colleagues,

You are already well aware that building energy optimization and sustainable development are on the same track. The building sector highly affects the critical issues of our generation, such as climate change, energy poverty, and the economic crisis. In most countries around the world, it is responsible for around 30–40% of energy consumption, with a similar share linked to greenhouse gas emissions. Therefore, the optimization of building energy design and retrofit is a “must” to promote sustainability. Indeed, such an achievement would yield substantial reductions of energy consumption, running costs, polluting emissions, other than improved indoor environmental quality. In this regard, a great deal of attention should be addressed to the energy retrofit of existing buildings, the turnover rate of the existing stock being very low (around 1%) in most countries, especially in developed ones. Finally, the words “sustainable”, “building”, “retrofit”, “energy”, and “optimization” (forming the SI title) provide concepts that need to be coupled to achieve a better life for us and our children.

In this frame, this Special Issue aims to propose a collection of worthy studies that combine the aforementioned concepts dealing with:

  • methodologies and/or case studies concerning sustainable building retrofit;
  • methodologies and/or case studies concerning the optimization of building energy retrofit;
  • methodologies and/or case studies concerning the energy retrofit of entire building stocks;
  • methodologies and/or case studies concerning the analysis and optimization of energy policies that drive building retrofit;
  • numerical/experimental studies addressing the investigation of innovative envelope components or energy systems for building retrofit.

Original papers related to the above topics and also dealing generally with methodologies, numerical and experimental investigations, case-studies addressing building retrofit are welcome.

Thank you for your contributions.

Prof. Gerardo Maria Mauro
Prof. Mohamed Hamdy
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sustainability is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • building retrofit
  • energy refurbishment
  • energy optimization
  • sustainability
  • energy efficiency
  • building energy performance
  • building performance simulation
  • building performance optimization
  • building envelope
  • energy systems
  • optimization methodologies

Published Papers (12 papers)

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Research

15 pages, 1127 KiB  
Article
Development of a Weight Factor Method for Sustainability Decisions in Building Renovation. Case Study Using Renobuild
by Alaa Khadra, Mårten Hugosson, Jan Akander and Jonn Are Myhren
Sustainability 2020, 12(17), 7194; https://doi.org/10.3390/su12177194 - 03 Sep 2020
Cited by 12 | Viewed by 2265
Abstract
Energy efficiency investments have become strategically important for the European Union. In particular, energy efficient renovation and investment in the existing building stock have become major challenges. Renovation of a building should involve a holistic and integrated design process, which considers all aspects [...] Read more.
Energy efficiency investments have become strategically important for the European Union. In particular, energy efficient renovation and investment in the existing building stock have become major challenges. Renovation of a building should involve a holistic and integrated design process, which considers all aspects of sustainability. The aim of this work is to suggest a mathematical model that weighs economic, social and ecological aspects into a measure that supports housing owners/decision makers to find the optimal renovation alternative from their perspective, taking factors such as budget, energy consumption, etc. into consideration. Multi-criteria decision-making (MCDM) concerns structuring and solving multiple-criteria decision problems. MCDM has become popular in energy planning as it enables the decision maker to pay attention to all the criteria available and make the appropriate decision as per the priority of the criteria. In this study, the concept is introduced based on economic, social and ecological aspects assessed during a renovation project. A pedagogical example illustrates the suggested numerical system for comparing different renovation alternatives. The suggested method will facilitate decision-making processes in renovation projects and will allow decision makers to choose the best renovation alternatives that are in line with their business ideas and principles. Full article
(This article belongs to the Special Issue Sustainable Building Retrofit and Energy Optimization)
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25 pages, 9440 KiB  
Article
Optimization Design and Test Bed of Fuzzy Control Rule Base for PV System MPPT in Micro Grid
by Jong-Chan Kim, Jun-Ho Huh and Jae-Sub Ko
Sustainability 2020, 12(9), 3763; https://doi.org/10.3390/su12093763 - 06 May 2020
Cited by 22 | Viewed by 2777
Abstract
This paper presents an optimal design of a fuzzy control rule base for tracking the maximum power point of a photovoltaic (PV) system. Fuzzy control is used for the maximum power point tracking (MPPT) of PV systems because it has the advantage of [...] Read more.
This paper presents an optimal design of a fuzzy control rule base for tracking the maximum power point of a photovoltaic (PV) system. Fuzzy control is used for the maximum power point tracking (MPPT) of PV systems because it has the advantage of processing nonlinear systems. The rule base of fuzzy control depends on the user or designer’s experience and determines the fuzzy control’s performance. In this paper, we divide the MPPT state of the PV system into four cases according to the operating conditions, and propose the rule base design of the fuzzy control according to each case. The proposed method in the paper tests the MPPT performance using artificial lighting and compares the results with the conventional control method (proportional and integral (PI) and perturbation & observation (P&O) method) to prove its effectiveness. Full article
(This article belongs to the Special Issue Sustainable Building Retrofit and Energy Optimization)
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19 pages, 4441 KiB  
Article
Effectiveness Evaluation of Financing Platform Operation of Buildings Energy Saving Transformation Using ANP-Fuzzy in China: An Empirical Study
by Handing Guo, Wanzhen Qiao and Yuehong Zheng
Sustainability 2020, 12(7), 2826; https://doi.org/10.3390/su12072826 - 02 Apr 2020
Cited by 4 | Viewed by 2481
Abstract
Building energy saving transformation is an inevitable requirement to achieve sustainable development, which can bring considerable economic, environmental, and social benefits. The key to healthy development of the market lies in the orderly operation of the financing platform. The effectiveness of the financing [...] Read more.
Building energy saving transformation is an inevitable requirement to achieve sustainable development, which can bring considerable economic, environmental, and social benefits. The key to healthy development of the market lies in the orderly operation of the financing platform. The effectiveness of the financing platform depends on scientific evaluation. Therefore, it is necessary to design a set of systematic and practical evaluation indicators for operational effectiveness of the buildings energy saving transformation financing platform, so as to provide reference for the effective operation of the financing platform, and provide measurement means for scholars to conduct quantitative research on the financing platform. This paper analyzes the effectiveness evaluation content for the financing platform operation of buildings energy saving transformation from the two levels of operation mechanism and operation subject behavior. Combined with the particularity of the financing platform of building energy saving transformation, the operational effectiveness evaluation index system of the financing platform is designed from three levels. The Analytic Network Process (ANP) method is applied to construct network structure, to describe element correlation, and to calculate index weight. The fuzzy comprehensive evaluation (Fuzzy) method was used to carry out quantitative evaluation of qualitative indicators. The Energy Performance Contracting (EPC) financing platform in Beijing was taken as an example to make an empirical analysis. The results show that the operational effectiveness evaluation system of the financing platform of buildings energy saving transformation constructed in this paper has certain practicability. In this evaluation system, scores of target consistency, the degree of information sharing among departments and coordination of operation mechanism are low. Finally, some policy suggestions are put forward to optimize financing platform of buildings energy saving transformation in China. Full article
(This article belongs to the Special Issue Sustainable Building Retrofit and Energy Optimization)
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16 pages, 5233 KiB  
Article
Retrofitting an Existing Office Building in the UAE Towards Achieving Low-Energy Building
by Maatouk Khoukhi, Abeer Fuad Darsaleh and Sara Ali
Sustainability 2020, 12(6), 2573; https://doi.org/10.3390/su12062573 - 24 Mar 2020
Cited by 16 | Viewed by 4210
Abstract
Retrofitting an existing building can oftentimes be more cost-effective than building a new facility. Since buildings consume a significant amount of energy, particularly for heating and cooling, and because existing buildings comprise the largest segment of the built environment, it is important to [...] Read more.
Retrofitting an existing building can oftentimes be more cost-effective than building a new facility. Since buildings consume a significant amount of energy, particularly for heating and cooling, and because existing buildings comprise the largest segment of the built environment, it is important to initiate energy conservation retrofits to reduce energy consumption and the cost of heating, cooling, and lighting buildings. However, conserving energy is not the only reason for retrofitting existing buildings. The goal should be to create a high-performance building by applying an integrated, whole-building design process to the project during the planning phase that ensures that all key design objectives are met. This paper presents a real case study of the retrofitting of an existing building to achieve lower energy consumption. Indeed, most of the constructed buildings in the UAE are unsuitable for the region, which is characterized by a very harsh climate that causes massive cooling loads and energy consumption due to an appropriate selection of design parameters at the design level. In this study, a monthly computer simulation of energy consumption of an office building in Sharjah was carried out under UAE weather conditions. Several parameters, including the building orientation, heating, ventilation, and air conditioning (HVAC) system, external shading, window-to-wall ratio, and the U-values of the walls and the roof, were investigated and optimized to achieve lower energy consumption. The simulation shows that the best case is 41.7% more efficient than the real (original) case and 30.6% more than the base case. The most sensitive parameter in the retrofitting alternatives is the roof component, which affects the energy savings by 8.49%, followed by the AC system with 8.34% energy savings if well selected using the base case. Among the selected five components, a new roof structure contributed the most to the decrease in the overall energy consumption (approximately 38%). This is followed by a new HVAC system, which leads to a 37% decrease, followed by a new wall type with insulation, resulting in a 20% decrease. Full article
(This article belongs to the Special Issue Sustainable Building Retrofit and Energy Optimization)
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24 pages, 19017 KiB  
Article
Comparative Whole Building Life Cycle Assessment of Energy Saving and Carbon Reduction Performance of Reinforced Concrete and Timber Stadiums—A Case Study in China
by Yu Dong, Tongyu Qin, Siyuan Zhou, Lu Huang, Rui Bo, Haibo Guo and Xunzhi Yin
Sustainability 2020, 12(4), 1566; https://doi.org/10.3390/su12041566 - 19 Feb 2020
Cited by 20 | Viewed by 4261
Abstract
Many stadiums will be built in China in the next few decades due to increasing public interest in physical exercise and the incentive policies issued by the government under its National Fitness Program. This paper investigates the energy saving and carbon reduction performance [...] Read more.
Many stadiums will be built in China in the next few decades due to increasing public interest in physical exercise and the incentive policies issued by the government under its National Fitness Program. This paper investigates the energy saving and carbon reduction performance of timber stadiums in China in comparison with stadiums constructed using conventional building materials, based on both life cycle energy assessment (LCEA) and life cycle carbon assessment (LCCA). The authors select five representative cities in five climate zones in China as the simulation environment, simulate energy use in the operation phase of stadiums constructed from reinforced concrete (RC) and timber, and compare the RC and timber stadiums in terms of their life cycle energy consumption and carbon emissions. The LCEA results reveal that the energy saving potential afforded by timber stadiums is 11.05%, 12.14%, 8.15%, 4.61% and 4.62% lower than those of RC buildings in “severely cold,” “cold,” “hot summer, cold winter,” “hot summer, warm winter,” and “temperate” regions, respectively. The LCCA results demonstrate that the carbon emissions of timber stadiums are 15.85%, 15.86%, 18.88%, 19.22% and 22.47% lower than those of RC buildings for the regions above, respectively. This demonstrates that in China, timber stadiums have better energy conservation and carbon reduction potential than RC stadiums, based on life cycle assessment. Thus, policy makers are advised to encourage the promotion of timber stadiums in China to achieve the goal of sustainable energy development for public buildings. Full article
(This article belongs to the Special Issue Sustainable Building Retrofit and Energy Optimization)
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35 pages, 9624 KiB  
Article
Maximizing Total Profit of Thermal Generation Units in Competitive Electric Market by Using a Proposed Particle Swarm Optimization
by Le Chi Kien, Thanh Long Duong, Van-Duc Phan and Thang Trung Nguyen
Sustainability 2020, 12(3), 1265; https://doi.org/10.3390/su12031265 - 10 Feb 2020
Cited by 3 | Viewed by 2454
Abstract
In the paper, a proposed particle swarm optimization (PPSO) is implemented for dealing with an economic load dispatch (ELD) problem considering the competitive electric market. The main task of the problem is to determine optimal power generation and optimal reserve generation of available [...] Read more.
In the paper, a proposed particle swarm optimization (PPSO) is implemented for dealing with an economic load dispatch (ELD) problem considering the competitive electric market. The main task of the problem is to determine optimal power generation and optimal reserve generation of available thermal generation units so that total profit of all the units is maximized. In addition, constraints, such as generation limit and reserve limit of each unit, power demand and reserve demand, must be exactly satisfied. PPSO is an improved version of conventional particle swarm optimization (PSO) by combining pseudo gradient method, constriction factor and a newly proposed position update method. On the other hand, in order to support PPSO to reach good results for the considered problem, a new constraint handling method (NCHM) is also proposed for determining maximum reserve generation and correcting reserve generation. Three test systems with 3, 10 and 20 units are employed to evaluate the real performance of PPSO. In addition to the comparisons with previous methods, salp swarm optimization (SSA), modified differential evolution (MDE) and eight other PSO methods are also implemented for comparisons. Through the result comparisons, two main contributions of the study are as follows: (1) NCHM is very effective for PSO methods to reach a high success rate and higher solution quality, (2) PPSO is more effective than other methods. Consequently, NCHM and PPSO are the useful combination for the considered problem. Full article
(This article belongs to the Special Issue Sustainable Building Retrofit and Energy Optimization)
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38 pages, 4907 KiB  
Article
Quantitative Analysis and Multi-Index Evaluation of the Green Building Envelope Performance in the Cold Area of China
by Shilei Lu, Zichen Wang and Tianshuai Zhang
Sustainability 2020, 12(1), 437; https://doi.org/10.3390/su12010437 - 06 Jan 2020
Cited by 10 | Viewed by 3815
Abstract
In China, relevant standards about building energy efficiency and green buildings have resulted in corresponding requirements for the envelope thermal performance. However, improvement of the thermal performance of the envelope is accompanied by an increase of the environmental impact and cost. This study [...] Read more.
In China, relevant standards about building energy efficiency and green buildings have resulted in corresponding requirements for the envelope thermal performance. However, improvement of the thermal performance of the envelope is accompanied by an increase of the environmental impact and cost. This study quantitatively analyzed the thermal performance, environmental impact, and cost of the green building envelope in cold areas and established a common practice database, as well as a multi-index evaluation model. The results show that the best thermal performance improvements are 40% in residential buildings and 30% in public buildings, respectively, based on the relevant standards. The exterior walls and windows have the greatest impact on building heat consumption. There is no significant correlation between the heat consumption and the comprehensive heat transfer coefficient of 10 green buildings. Therefore, the comprehensive heat loss coefficient is corrected. The verification results show that all errors except project 10 are within 15%. Additionally, the projects with balanced thermal performance improvement of exterior walls and windows showed a better performance. Finally, the best combination of residential building envelopes in the cold area was selected, using the evaluation model and quantitative database to calculate the comprehensive score. Full article
(This article belongs to the Special Issue Sustainable Building Retrofit and Energy Optimization)
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23 pages, 4480 KiB  
Article
Energy and Economic Analysis of Tropical Building Envelope Material in Compliance with Thailand’s Building Energy Code
by Pathomthat Chiradeja and Atthapol Ngaopitakkul
Sustainability 2019, 11(23), 6872; https://doi.org/10.3390/su11236872 - 03 Dec 2019
Cited by 11 | Viewed by 3919
Abstract
The building envelope has a direct impact on the overall energy consumption of a building. Thus, an improvement in the building envelope using energy-efficient material can yield the desired energy performance. This study is based on the materials and compositions used in building [...] Read more.
The building envelope has a direct impact on the overall energy consumption of a building. Thus, an improvement in the building envelope using energy-efficient material can yield the desired energy performance. This study is based on the materials and compositions used in building envelopes in compliance with the building energy code of Thailand. The building under study is an educational building located in Bangkok, Thailand. Both the energy and the economic aspects of retrofitted building envelopes are discussed in this study. The energy performance was evaluated by calculating the thermal transfer value and whole building energy consumption using the building energy code (BEC) software. The simulation was done under the assumption that the building envelope in the case study building was retrofitted with different materials and compositions. The study determines the feasibility of retrofitting buildings using energy-efficient material by utilizing the discounted payback period and internal rate of return (IRR) as indicators. The results show that retrofitted building envelopes in every case can reduce the whole building energy consumption. In the best envelope configuration, energy consumption can decrease by 65%. In addition, the economic potential is also high, with an IRR value of approximately 15% and a payback period of 23 less than nine years. These finding indicate that a building envelope made with energy-efficient material can achieve good results for both energy performance and economic feasibility. Full article
(This article belongs to the Special Issue Sustainable Building Retrofit and Energy Optimization)
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13 pages, 4010 KiB  
Article
Cooling Load Forecasting via Predictive Optimization of a Nonlinear Autoregressive Exogenous (NARX) Neural Network Model
by Jee-Heon Kim, Nam-Chul Seong and Wonchang Choi
Sustainability 2019, 11(23), 6535; https://doi.org/10.3390/su11236535 - 20 Nov 2019
Cited by 14 | Viewed by 1953
Abstract
Accurate calculations and predictions of heating and cooling loads in buildings play an important role in the development and implementation of building energy management plans. This study aims to improve the forecasting accuracy of cooling load predictions using an optimized nonlinear autoregressive exogenous [...] Read more.
Accurate calculations and predictions of heating and cooling loads in buildings play an important role in the development and implementation of building energy management plans. This study aims to improve the forecasting accuracy of cooling load predictions using an optimized nonlinear autoregressive exogenous (NARX) neural network model. The preprocessing of training data and optimization of parameters were investigated for model optimization. In predictive models of cooling loads, the removal of missing values and the adjustment of structural parameters have been shown to help improve the predictive performance of a neural network model. In this study, preprocessing the training data eliminated missing values for times when the heating, ventilation, and air-conditioning system is not running. Also, the structural and learning parameters were adjusted to optimize the model parameters. Full article
(This article belongs to the Special Issue Sustainable Building Retrofit and Energy Optimization)
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24 pages, 11005 KiB  
Article
A Study on the Improvement of Double-Skin Facade Operation for Reducing Heating Load in Winter
by Uk-Joo Sung and Seok-Hyun Kim
Sustainability 2019, 11(22), 6238; https://doi.org/10.3390/su11226238 - 07 Nov 2019
Cited by 4 | Viewed by 2593
Abstract
A double-skin facade makes it possible to gain irradiance through the glass on the outer side in summer, and to increase the temperature of air flowing in the cavity so as to induce the flow of air current. Therefore, a double-skin facade is [...] Read more.
A double-skin facade makes it possible to gain irradiance through the glass on the outer side in summer, and to increase the temperature of air flowing in the cavity so as to induce the flow of air current. Therefore, a double-skin facade is able to reduce the load of the outer skin, which is delivered from the outside to the inside in summer, and to serve as a buffer space for the internal and external environments in winter, and thereby prevent heat loss from the building envelope. Theoretical analysis was conducted to review the heat effects of a double-skin facade and to evaluate the performance of a plan for indoor load reduction. This study carried out a field measurement of a building with a double-skin facade and then analyzed the thermal phenomenon occurring in between the outer skin of the outside and the skin of the inside facing the building surface, according to the effects of irradiance going into the double-skin facade cavity. In order to propose an indoor air conditioning energy reduction plan using preheated air through the double-skin facade, this study utilized a building simulation to be implemented on the target building and then analyzed the effects of the improvement plan for the double-skin facade. A simulation model was suggested that implemented the aforementioned airflow network and analyzed the ventilation performance and energy performance according to the application of alternative plans and thermal effect. To find the actual state of operation of the double-skin facade in winter, this study measured the target building. A solar chimney-based double-skin facade was analyzed in winter. As a result, with the application of a solar chimney and a rise in its height, the available capacity of relatively larger solar heat increased, and therefore the proposed plan had excellent performance in terms of heating energy saving. When the thermal effect was applied to the solar chimney, the heating energy use effect of the solar irradiance of the double-skin facade was larger. When thermal effect was applied to a three-floor solar chimney, the heating energy use increased to about 7.6 times higher than that of the original performance of the double-skin facade. Full article
(This article belongs to the Special Issue Sustainable Building Retrofit and Energy Optimization)
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18 pages, 9631 KiB  
Article
New Building Cladding System Using Independent Tilted BIPV Panels with Battery Storage Capability
by Amy A. Kim, Dorothy A. Reed, Youngjun Choe, Shuoqi Wang and Carolina Recart
Sustainability 2019, 11(20), 5546; https://doi.org/10.3390/su11205546 - 09 Oct 2019
Cited by 11 | Viewed by 7782
Abstract
In order to meet renewable energy goals in the near future, the deployment of photovoltaic (PV) panels on buildings will dramatically increase. The objective of this paper is to introduce an improved design for PV cladding systems that will greatly contribute to meeting [...] Read more.
In order to meet renewable energy goals in the near future, the deployment of photovoltaic (PV) panels on buildings will dramatically increase. The objective of this paper is to introduce an improved design for PV cladding systems that will greatly contribute to meeting these renewable energy goals. Typically, building-integrated photovoltaic (BIPV) panels are vertically oriented as cladding and they are not coupled with individual storage batteries. The proposed cladding couples a tilted BIPV panel with one or more storage batteries at each building placement. Thus, the tilted BIPV plus battery system is independent of other power generation in the building and it is referred to as a “building perma-power link” (BPPL) cladding element. Each cladding panel is designed as a stand-alone system, which will be useful for installation, operation, and maintenance. The hyper-redundancy of multiple BPPL cladding panels for a typical building significantly enhances its overall energy resiliency. In order to foster manufacturing ease, each individual cladding unit has been designed at tilts of 45° and 60°. An example of a mid-rise building in Seattle, Washington is provided. The degree of building energy resiliency provided through multiple BPPLs is examined. Full article
(This article belongs to the Special Issue Sustainable Building Retrofit and Energy Optimization)
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19 pages, 4884 KiB  
Article
Axial Compression Performance of Post-Fire Concrete Columns Strengthened Using Thin-Walled Steel Tubes
by Yi Luo, Jiapeng Su, Yuye Xu, Tingru Ou and Xingqian Peng
Sustainability 2019, 11(18), 4971; https://doi.org/10.3390/su11184971 - 11 Sep 2019
Cited by 4 | Viewed by 2335
Abstract
For concrete columns damaged by fire, a strengthen technique using thin-walled steel tubes is proposed. To investigate the axial compression capacity of post-fire concrete columns strengthened using thin-walled steel tubes, considering tube thickness, the strengthening method, and section geometry, 12 specimens were fabricated, [...] Read more.
For concrete columns damaged by fire, a strengthen technique using thin-walled steel tubes is proposed. To investigate the axial compression capacity of post-fire concrete columns strengthened using thin-walled steel tubes, considering tube thickness, the strengthening method, and section geometry, 12 specimens were fabricated, of which two were control columns and 10 were exposed to fire in accordance with the ISO834 temperature curve. Subsequently, eight specimens were strengthened. Axial compression tests were conducted to provide a better understanding of the strengthening technique. The experiments indicated that: (1) Different failure modes were observed for different cross section geometry—local bucking for square sections, and shear failure for circular sections. (2) The stiffness, axial strength, and ultimate deformation capacity of the enhanced columns may be rehabilitated and even better than the undamaged ones. (3) Two enhancement methods were compared. The steel tubes act as restraints, are merely subjected to tension, and provide strong restraint to the core concrete. The tube carrying load together with the concrete columns are mainly subject to compression, and likely to buckle with longitudinal strain. Finally, axial compressive equations of post-fire reinforced concrete (RC) with thin-wall steel tubes, including both square sections and circle sections, were proposed on the mechanism of concrete filled steel tubes. Full article
(This article belongs to the Special Issue Sustainable Building Retrofit and Energy Optimization)
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