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Dr. Esther Obonyo
Rinker School of Building Construction, University of Florida, PO Box 115703 (or Rinker 304), Gainesville, FL 32611-5703, USA

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0 Productivity Improvement
0 green building materials
0 sustainable building technologies
0 earth-based bricks
0 sustainable composite and hybrid materials

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Journal article
Published: 14 July 2021 in Energies
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Different methods to achieve zero-energy and low carbon on the scale of a building are shown by most of the research works. Despite this, the recommendations generally offered by researchers do not always correspond to the realities found during the construction of new buildings in a determined region. Therefore, a standard may not be valid in all climate regions of the world. Being aware of this fact, a study was carried out to analyse the design of new buildings respecting the “zero-energy and low carbon emission” concept in tropical climatic regions when they are compared with a base case of temperate regions. To reach this objective, the comparison between real and simulated data from the different buildings studied was developed. The results showed that the renovation of existing residential buildings allows for reducing up to 35% of energy demand and a great quantity of CO2 emissions in both climate types. Despite this, the investment rate linked to the construction of zero-energy buildings in tropical zones is 12 times lower than in temperate zones and the payback was double. In particular, this effect can be related to the efficiency of photovoltaic panels, which is estimated to be, at least, 34% higher in tropical zones than temperate zones. Finally, this study highlights the interest and methodology to implement zero-energy buildings in tropical regions.

ACS Style

Modeste Nematchoua; José Orosa; Paola Ricciardi; Esther Obonyo; Eric Sambatra; Sigrid Reiter. Transition to Zero Energy and Low Carbon Emission in Residential Buildings Located in Tropical and Temperate Climates. Energies 2021, 14, 4253 .

AMA Style

Modeste Nematchoua, José Orosa, Paola Ricciardi, Esther Obonyo, Eric Sambatra, Sigrid Reiter. Transition to Zero Energy and Low Carbon Emission in Residential Buildings Located in Tropical and Temperate Climates. Energies. 2021; 14 (14):4253.

Chicago/Turabian Style

Modeste Nematchoua; José Orosa; Paola Ricciardi; Esther Obonyo; Eric Sambatra; Sigrid Reiter. 2021. "Transition to Zero Energy and Low Carbon Emission in Residential Buildings Located in Tropical and Temperate Climates." Energies 14, no. 14: 4253.

Journal article
Published: 13 February 2021 in Sensors
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Construction workers executing manual-intensive tasks are susceptible to musculoskeletal disorders (MSDs) due to overexposure to awkward postures. Automated posture recognition and assessment based on wearable sensor output can help reduce MSDs risks through early risk-factor detection. However, extant studies mainly focus on optimizing recognition models. There is a lack of studies exploring the design of a wearable sensing system that assesses the MSDs risks based on detected postures and then provides feedback for injury prevention. This study aims at investigating the design of an effective wearable MSDs prevention system. This study first proposes the design of a wearable inertial measurement unit (IMU) sensing system, then develops the prototype for end-user evaluation. Construction workers and managers evaluated a proposed system by interacting with wearable sensors and user interfaces (UIs), followed by an evaluation survey. The results suggest that wearable sensing is a promising approach for collecting motion data with low discomfort; posture-based MSDs risk assessment has a high potential in improving workers’ safety awareness; and mobile- and cloud-based UIs can deliver the risk assessment information to end-users with ease. This research contributes to the design, development, and validation of wearable sensing-based injury prevention systems, which may be adapted to other labor-intensive occupations.

ACS Style

Junqi Zhao; Esther Obonyo; Sven Bilén. Wearable Inertial Measurement Unit Sensing System for Musculoskeletal Disorders Prevention in Construction. Sensors 2021, 21, 1324 .

AMA Style

Junqi Zhao, Esther Obonyo, Sven Bilén. Wearable Inertial Measurement Unit Sensing System for Musculoskeletal Disorders Prevention in Construction. Sensors. 2021; 21 (4):1324.

Chicago/Turabian Style

Junqi Zhao; Esther Obonyo; Sven Bilén. 2021. "Wearable Inertial Measurement Unit Sensing System for Musculoskeletal Disorders Prevention in Construction." Sensors 21, no. 4: 1324.

Journal article
Published: 14 October 2020 in Cities & Health
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ACS Style

Esther Obonyo; James Mutunga. A global building network research for advancing healthy and affordable housing. Cities & Health 2020, 1 -4.

AMA Style

Esther Obonyo, James Mutunga. A global building network research for advancing healthy and affordable housing. Cities & Health. 2020; ():1-4.

Chicago/Turabian Style

Esther Obonyo; James Mutunga. 2020. "A global building network research for advancing healthy and affordable housing." Cities & Health , no. : 1-4.

Journal article
Published: 24 September 2020 in Advanced Engineering Informatics
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This paper proposes using Deep Neural Networks (DNN) models for recognizing construction workers’ postures from motion data captured by wearable Inertial Measurement Units (IMUs) sensors. The recognized awkward postures can be linked to known risks of Musculoskeletal Disorders among workers. Applying conventional Machine Learning (ML)-based models has shown promising results in recognizing workers’ postures. ML models are limited – they reply on heuristic feature engineering when constructing discriminative features for characterizing postures. This makes further improving the model performance regarding recognition accuracy challenging. In this paper, the authors investigate the feasibility of addressing this problem using a DNN model that, through integrating Convolutional Neural Networks (CNN) with Long Short-Term Memory (LSTM) layers, automates feature engineering and sequential pattern detection. The model’s recognition performance was evaluated using datasets collected from four workers on construction sites. The DNN model integrating one convolutional and two LSTM layers resulted in the best performance (measured by F1 Score). The proposed model outperformed baseline CNN and LSTM models suggesting that it leveraged the advantages of the two baseline models for effective feature learning. It improved benchmark ML models’ recognition performance by an average of 11% under personalized modelling. The recognition performance was also improved by 3% when the proposed model was applied to 8 types of postures across three subjects. These results support that the proposed DNN model has a high potential in addressing challenges for improving the recognition performance that was observed when using ML models.

ACS Style

Junqi Zhao; Esther Obonyo. Convolutional long short-term memory model for recognizing construction workers’ postures from wearable inertial measurement units. Advanced Engineering Informatics 2020, 46, 101177 .

AMA Style

Junqi Zhao, Esther Obonyo. Convolutional long short-term memory model for recognizing construction workers’ postures from wearable inertial measurement units. Advanced Engineering Informatics. 2020; 46 ():101177.

Chicago/Turabian Style

Junqi Zhao; Esther Obonyo. 2020. "Convolutional long short-term memory model for recognizing construction workers’ postures from wearable inertial measurement units." Advanced Engineering Informatics 46, no. : 101177.

Journal article
Published: 25 November 2019 in Renewable Energy
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Although the study of roofing systems (from coverings to structure of the roof) is of great significance to energy efficiency and sustainable development, design and construction of new roofs on top of existing roofs in buildings has not received sufficient attention. This study discusses re-roofing as one of the key options to reduce energy consumption and improve overall building performance. The more conventional choice and more frequently chosen option for building energy retrofit is vertical building envelope components, however, this paper presents the case study of a proposed retrofitting concept for the roof of an existing building. Using a simulation methodology, the research demonstrates how the proposed retrofitting concept improves the energy performance using electricity generated and external conduction gain as evaluation metrics. The proposed novel re-roofing concept consists of thermal insulation, waterproofing and electric energy generation properties. More specifically, the design concept includes a three-layer roofing system consisting of (from exterior toward interior): a PV panel, an EPDM membrane and an insulation layer. The main goal of this study is to develop a concept for an innovative re-roofing solution that demonstrates the feasibility of turning an old building into a watertight and energy producing system.

ACS Style

Shahryar Habibi; Esther Adhiambo Obonyo; Ali M. Memari. Design and development of energy efficient re-roofing solutions. Renewable Energy 2019, 151, 1209 -1219.

AMA Style

Shahryar Habibi, Esther Adhiambo Obonyo, Ali M. Memari. Design and development of energy efficient re-roofing solutions. Renewable Energy. 2019; 151 ():1209-1219.

Chicago/Turabian Style

Shahryar Habibi; Esther Adhiambo Obonyo; Ali M. Memari. 2019. "Design and development of energy efficient re-roofing solutions." Renewable Energy 151, no. : 1209-1219.

Review
Published: 21 December 2018 in Buildings
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Although significant efforts have been made to combat the spread of vector-borne diseases (VBDs), they still account for more than 17% of all infectious diseases. According to the World Health Organization (WHO), there were 216 million estimated cases in 2016. The efforts that resulted in these positive outcomes lack long-term financial sustainability because of the significant amount of funding involved. There is, therefore, a need for more cost-effective intervention. The authors contend that design decisions in the built environment can have a positive impact on the efforts directed at mitigating the risk of malaria in a more cost-effective manner. It is known that the built environment, through features such as openings, can propagate the spread of malaria. There have been some significant efforts directed at addressing this risk. This notwithstanding, an extensive review of closely related work established that built environment professionals have limited access to information on specific ways through which their design decisions can contribute to mitigating the risk of malaria. The validity of this hypothesis was tested through evaluating the opportunities for synergies in selected parts of East Africa. Secondary data derived from relevant urban health journals as well as repositories curated by leading health agencies such as WHO were synthesized and analyzed using a web of causation approach. The outcome of the analysis is a schema of primary and secondary source (risk) factors. The use of the web of causation approach revealed the existing factor-to-factor interactions that could have a reinforcing effect. This information was used to identify the critical linkages and interdependencies across different factors. The outcome of the analysis was mapped against risk factors that can be linked to decisions made during the six primary phases of the construction life cycle: Preliminary phase, conceptual design, detailed design, construction, facilities management, and end of life/disuse. A conceptual architecture for a decision support framework has been proposed and will be developed into a prototype in subsequent efforts.

ACS Style

Esther Obonyo; Sumit Pareek; Dawit Okubatsion Woldu. Decision Making within the Built Environment as a Strategy for Mitigating the Risk of Malaria and Other Vector-Borne Diseases. Buildings 2018, 9, 2 .

AMA Style

Esther Obonyo, Sumit Pareek, Dawit Okubatsion Woldu. Decision Making within the Built Environment as a Strategy for Mitigating the Risk of Malaria and Other Vector-Borne Diseases. Buildings. 2018; 9 (1):2.

Chicago/Turabian Style

Esther Obonyo; Sumit Pareek; Dawit Okubatsion Woldu. 2018. "Decision Making within the Built Environment as a Strategy for Mitigating the Risk of Malaria and Other Vector-Borne Diseases." Buildings 9, no. 1: 2.

Preprint
Published: 05 November 2018
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Although significant efforts have been made to combat the spread of vector-borne diseases (VBDs), they still account for more than 17% of all infectious diseases. According to the World Health Organization (WHO), there were 216 million estimated cases in 2016, which is a 9.3% decrease from the estimated cases reported one decade earlier. It is known that the built environment, through features such as openings, can propagate the spread of malaria. There have been some significant efforts directed at addressing this risk. This notwithstanding, there are some knowledge gaps that have resulted in a missed opportunity for synergistically tackling the problem of vectors through leveraging design decisions made by built environment professionals. This work assesses the extent to which design decisions in the built environment can have a positive impact on the efforts directed at mitigating the risk of malaria based on selected cases from East Africa. Secondary data derived from relevant urban health journals as well as repositories curated by leading health agencies such as WHO were synthesized and analyzed using a web of causation approach. The outcome of the analysis is a schema of primary and secondary source (risk) factors. The use of the web of causation approach revealed the existing factor-to-factor interactions that could have a reinforcing effect. This information was used to identify the critical linkages and interdependencies across different factors. The outcome of the analysis was mapped against risk factors that can be linked to decisions made during the six primary phases of the construction life cycle: preliminary phase, conceptual design, detailed design, construction, facilities management, and end of life/disuse. The findings of the research have established that 1) there is, in fact, a built environment–related opportunity that can be leveraged to advance the impact of malaria mitigation effort; 2) cross-disciplinary synergies are critical to managing the interdependencies and complexity of malaria risk factors that have a reinforcing effect; and 3) a knowledge-management framework that serves as a decision support tool would be valuable for sharing data under a push-and-pull mechanism, in which data shared in real time can address the timeliness of mitigating the spread of malaria at the earliest stages for the greatest impact. Based on the findings, a conceptual architecture for a decision support framework has been proposed. This will be developed into a knowledge-management platform in subsequent efforts.

ACS Style

Esther Obonyo; Sumit Pareek; Dawit Okubatsion Woldu. Decision Making within the Built Environment as a Strategy for Mitigating the Risk of Malaria and other Vector-Borne Diseases. 2018, 1 .

AMA Style

Esther Obonyo, Sumit Pareek, Dawit Okubatsion Woldu. Decision Making within the Built Environment as a Strategy for Mitigating the Risk of Malaria and other Vector-Borne Diseases. . 2018; ():1.

Chicago/Turabian Style

Esther Obonyo; Sumit Pareek; Dawit Okubatsion Woldu. 2018. "Decision Making within the Built Environment as a Strategy for Mitigating the Risk of Malaria and other Vector-Borne Diseases." , no. : 1.

Journal article
Published: 29 June 2015 in Materials & Design
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Earthen construction materials are often ecologically friendly and locally available. They are however weaker and poor in damage resilience compared to mainstream walling materials like fired bricks and concrete masonry units (CMU). Compressed earth blocks (CEB), a modern form of the adobe brick, are gaining popularity as a construction material globally because they are stronger and more dimensionally stable compared to earlier forms of earthen construction methods/techniques. Despite the strength improvement achieved through using CEBs over other traditional forms of earthen construction, they are still more brittle and weaker in bending and compression in comparison to CMU and fired bricks. This research investigated the potential of addressing some of the shortcomings of earthen construction materials by assessing the influence of polypropylene fibers on the strength, ductility, and deformability of CEBs. CEBs were produced using different fiber weight fractions and tested in both compression and bending. Overall, performance in bending and ductility were improved by the addition of fibers. The quantity of fibers present was found to have an influence on block strength, post-crack response, and deformability. The findings presented in this paper suggest that polypropylene fibers are a feasible fiber option for CEB production.

ACS Style

Peter Donkor; Esther Obonyo. Earthen construction materials: Assessing the feasibility of improving strength and deformability of compressed earth blocks using polypropylene fibers. Materials & Design 2015, 83, 813 -819.

AMA Style

Peter Donkor, Esther Obonyo. Earthen construction materials: Assessing the feasibility of improving strength and deformability of compressed earth blocks using polypropylene fibers. Materials & Design. 2015; 83 ():813-819.

Chicago/Turabian Style

Peter Donkor; Esther Obonyo. 2015. "Earthen construction materials: Assessing the feasibility of improving strength and deformability of compressed earth blocks using polypropylene fibers." Materials & Design 83, no. : 813-819.

Journal article
Published: 01 October 2014 in Cement and Concrete Composites
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ACS Style

Elie Kamseu; Maria Cannio; Esther A. Obonyo; Fey Tobias; Maria Chiara Bignozzi; Vincenzo M. Sglavo; Cristina Leonelli. Metakaolin-based inorganic polymer composite: Effects of fine aggregate composition and structure on porosity evolution, microstructure and mechanical properties. Cement and Concrete Composites 2014, 53, 258 -269.

AMA Style

Elie Kamseu, Maria Cannio, Esther A. Obonyo, Fey Tobias, Maria Chiara Bignozzi, Vincenzo M. Sglavo, Cristina Leonelli. Metakaolin-based inorganic polymer composite: Effects of fine aggregate composition and structure on porosity evolution, microstructure and mechanical properties. Cement and Concrete Composites. 2014; 53 ():258-269.

Chicago/Turabian Style

Elie Kamseu; Maria Cannio; Esther A. Obonyo; Fey Tobias; Maria Chiara Bignozzi; Vincenzo M. Sglavo; Cristina Leonelli. 2014. "Metakaolin-based inorganic polymer composite: Effects of fine aggregate composition and structure on porosity evolution, microstructure and mechanical properties." Cement and Concrete Composites 53, no. : 258-269.

Journal article
Published: 25 August 2014 in Sustainability
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Two iron-rich clayey materials (L1 and L2, with the main difference being the level of iron accumulation) have been studied for their suitability as solid precursors for inorganic polymer composites. L1, with the lower iron content, was calcined at 700°C for 4 h and used as replacement, in the range of 15–35 wt%, for both raw laterites in the formulations of geopolymeric composites. The different mixtures were activated with a highly concentrated alkaline solution containing sodium hydroxide and sodium silicate. River sand with semi-crystalline structure was added to form semi-dry pastes which were pressed to appropriate shape. X-ray diffraction, Infrared spectroscopy, Scanning Electron Microscopy and Mercury Intrusion Porosimetry results demonstrated the effectiveness of the calcined fraction of L1 to act as nucleation sites and extend the geopolymerization to the matrix composites. A highly compact matrix with low porosity and good stability in water, together with a strength comparable to that of standard concretes was obtained allowing for conclusions to be made on the quality of laterites as promising solid precursor for sustainable, environmentally-friendly, and cost-efficient structural materials.

ACS Style

Esther A. Obonyo; Elie Kamseu; Patrick N. Lemougna; Arlin B. Tchamba; Uphie C. Melo; Cristina Leonelli. A Sustainable Approach for the Geopolymerization of Natural Iron-Rich Aluminosilicate Materials. Sustainability 2014, 6, 5535 -5553.

AMA Style

Esther A. Obonyo, Elie Kamseu, Patrick N. Lemougna, Arlin B. Tchamba, Uphie C. Melo, Cristina Leonelli. A Sustainable Approach for the Geopolymerization of Natural Iron-Rich Aluminosilicate Materials. Sustainability. 2014; 6 (9):5535-5553.

Chicago/Turabian Style

Esther A. Obonyo; Elie Kamseu; Patrick N. Lemougna; Arlin B. Tchamba; Uphie C. Melo; Cristina Leonelli. 2014. "A Sustainable Approach for the Geopolymerization of Natural Iron-Rich Aluminosilicate Materials." Sustainability 6, no. 9: 5535-5553.

Proceedings article
Published: 13 May 2014 in Construction Research Congress 2014
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In addition to addressing the basic need of shelter, building envelopes must address concerns of load transfer, energy efficiency, durability, and resilience with respect to natural and human-produced disasters, among other structural and aesthetic concerns. This paper discusses the key barriers to the use of low-tech compressed earth blocks in a resilient and sustainable manner. The paper also presents a process improvement approach through which low-tech masonry approaches can be used to provide a context-appropriate, cost-effective resilient solution. Typical compressive strength values of masonry can range from 7 MPa to 20 MPa for commonly used concrete masonry units (CMU). Compressed earthen masonry usually peaks at somewhere between 3 and 5 MPa. When working with these lower numbers, general concerns arise from masonry being an elastic-brittle material and become more significant. This paper adopts a process improvement approach to propose a stabilization strategy that can be used to enhance the quality of blocks produced. Fibers are included in the blocks in this research to address susceptibility to local failure when the masonry is exposed to impact load from, for example, flying debris in a high wind region. The process improvement approach is used to optimize the use of fiber in compressed earth blocks and also explore the feasibility of using a low-strength, soil-cement mortar to achieve strength compatibility with the optimized blocks.

ACS Style

Esther Obonyo; Peter Donkor; Fabio Matta; Ece Erdogmus. Challenges, Opportunities, and Solutions in Low-cost Building Envelopes: A Case Study of Low-strength Masonry Systems. Construction Research Congress 2014 2014, 564 -573.

AMA Style

Esther Obonyo, Peter Donkor, Fabio Matta, Ece Erdogmus. Challenges, Opportunities, and Solutions in Low-cost Building Envelopes: A Case Study of Low-strength Masonry Systems. Construction Research Congress 2014. 2014; ():564-573.

Chicago/Turabian Style

Esther Obonyo; Peter Donkor; Fabio Matta; Ece Erdogmus. 2014. "Challenges, Opportunities, and Solutions in Low-cost Building Envelopes: A Case Study of Low-strength Masonry Systems." Construction Research Congress 2014 , no. : 564-573.

Conference paper
Published: 13 May 2014 in Construction Research Congress 2014
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Earthen masonry generally is brittle, weak, and poor in damage resilience. There is historical evidence that natural fibers, such as straw and horsehair, have been used to reinforce earthen masonry to prevent desiccation cracks and improve tensile strength. However, fibers also have been known to affect mechanical properties negatively, such as with compressive strength (an important quality control parameter for load-bearing masonry) by creating voids and lowering density. This paper reports on findings of a study directed at investigating the feasibility of avoiding such problems in compressed and stabilized earth blocks through optimizing the fiber length when using soil from Newberry, FL. Standard polypropylene fibers were selected for the study. The two lengths of fibers studied were 54 mm and 27 mm. The test results showed a general improvement in compressive strength of the fiber reinforced matrices compared to the unreinforced ones. Although an improvement in modulus of rupture (MOR) was observed for matrices reinforced with 54 mm fibers, results varied for the other fiber-reinforced matrices. An improvement in post-initial crack behavior was observed for all fiber-reinforced matrices compared to the unreinforced ones. The 54 mm fibers yielded the best results based on the influence on MOR, compressive strength, and deformability compared with the other matrices.

ACS Style

Peter Donkor; Esther Obonyo; Fabio Matta; Ece Erdogmus. Effect of Polypropylene Fiber Length on the Flexural and Compressive Strength of Compressed Stabilized Earth Blocks. Construction Research Congress 2014 2014, 1 .

AMA Style

Peter Donkor, Esther Obonyo, Fabio Matta, Ece Erdogmus. Effect of Polypropylene Fiber Length on the Flexural and Compressive Strength of Compressed Stabilized Earth Blocks. Construction Research Congress 2014. 2014; ():1.

Chicago/Turabian Style

Peter Donkor; Esther Obonyo; Fabio Matta; Ece Erdogmus. 2014. "Effect of Polypropylene Fiber Length on the Flexural and Compressive Strength of Compressed Stabilized Earth Blocks." Construction Research Congress 2014 , no. : 1.

Proceedings article
Published: 05 April 2013 in AEI 2013
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Standards and codes can play a key role in the social acceptability of earthen masonry. This notwithstanding, the existing regulatory framework for earth-based masonry construction is limited to derivatives of performance standards and codes that were developed for concrete masonry units. The discussion in this paper presented work directed at contributing the development of a reliable resting regime for interlocking bricks. The different testing regimes investigated include crushing full-sized blocks (horizontally), 2-inch and 1.18-inch cubes and units with filled recesses testing in compliance with the provisions of ASTM C140-12, Standard Test Methods for Sampling and Testing Concrete Masonry Units and Related Units. The findings have revealed that the numbers obtained for compressive strength change depending on the testing regime. In addition, the recorded values for compressive strengths were much higher when the samples were tested based on the provisions of ASTM C140-12, Standard Test Methods for Sampling and Testing Concrete Masonry Units and Related Units. As this procedure accounts for the unit geometric properties of the interlocking block, the results suggest that it is a more reliable testing regime.

ACS Style

E. A. Obonyo; P. Donkor; M. Baskaran; F. Amezugbe. Advancing the Structural Use of Earth-based Bricks: Assessing the Reliability of Existing Testing Procedures. AEI 2013 2013, 988 -996.

AMA Style

E. A. Obonyo, P. Donkor, M. Baskaran, F. Amezugbe. Advancing the Structural Use of Earth-based Bricks: Assessing the Reliability of Existing Testing Procedures. AEI 2013. 2013; ():988-996.

Chicago/Turabian Style

E. A. Obonyo; P. Donkor; M. Baskaran; F. Amezugbe. 2013. "Advancing the Structural Use of Earth-based Bricks: Assessing the Reliability of Existing Testing Procedures." AEI 2013 , no. : 988-996.

Journal article
Published: 01 March 2013 in Journal of Computing in Civil Engineering
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Many construction industry–specific, agent-based applications have been deployed to enhance knowledge systems. These applications are generally agent-centered multi-agent systems (ACMAS). Interaction between ACMAS agents is designed around the internal mental states of an agent and the relationship between these states and its overall behavior. Communication in this approach comprises speech acts whose meaning can be described in terms of the mental states of an agent. This interaction protocol makes it difficult for agents that have been implemented using different approaches to communicate. This paper reviews the potential for addressing this limitation through using organization-centered multi-agent systems (OCMAS) in which agent interaction is designed around macro-level concepts such as organizations, groups, communities, and roles. Although the use of organizational metaphors in agent-based application is still in its infancy, there are some emerging modeling tools that can be used to advance the existing agent-based applications into open MASs that exhibit the dynamic and flexible characteristics of open, distributed systems. The paper illustrates this potential by using a proof of concept based on decision support requirements for highway maintenance management.

ACS Style

E. Obonyo. Enhancing Intelligent Knowledge Systems Using Organization-Centered Agent Models. Journal of Computing in Civil Engineering 2013, 27, 196 -201.

AMA Style

E. Obonyo. Enhancing Intelligent Knowledge Systems Using Organization-Centered Agent Models. Journal of Computing in Civil Engineering. 2013; 27 (2):196-201.

Chicago/Turabian Style

E. Obonyo. 2013. "Enhancing Intelligent Knowledge Systems Using Organization-Centered Agent Models." Journal of Computing in Civil Engineering 27, no. 2: 196-201.

Proceedings article
Published: 11 June 2012 in Computing in Civil Engineering (2012)
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Maintaining the infrastructure involves managing structural elements requiring different maintenance strategies. Some elements have to be maintained at regular intervals based on a pre-programmed routine. Other elements are inspected at regular intervals and the specific the requirements for maintenance remain unknown until after the inspection. The latter complicates job scheduling as it disrupts existing programs for routine maintenance. Conventional maintenance planning systems lack dynamism and/ or fail to acknowledge all relations between actors, activities and resources. This paper discusses the potential of addressing these challenges using an organization-centered agent-modeling approach where different scenarios are encapsulated in agent models which captures: 1) global organization strategy and goals, and 2) the objectives and requirements of different stakeholders. Specific challenges of maintenance planning that cannot be fully addressed using conventional tools have been identified. The paper describes implemented of proof-of-concept organization-centered agent models that capture the requirements of maintenance planning.

ACS Style

E. Obonyo; C. Anumba. Organization-Centered Multi-Agent Systems for Dynamic Highway Maintenance Planning. Computing in Civil Engineering (2012) 2012, 1 .

AMA Style

E. Obonyo, C. Anumba. Organization-Centered Multi-Agent Systems for Dynamic Highway Maintenance Planning. Computing in Civil Engineering (2012). 2012; ():1.

Chicago/Turabian Style

E. Obonyo; C. Anumba. 2012. "Organization-Centered Multi-Agent Systems for Dynamic Highway Maintenance Planning." Computing in Civil Engineering (2012) , no. : 1.

Article
Published: 28 February 2012 in Architectural Engineering and Design Management
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The research reported in this article is based on an NSF (National Science Foundation) project aimed at advancing the structural use of earth-based technologies through addressing durability concerns within the hot and humid context. This article focuses on one aspect of the research directed at developing an enhanced, lignocellulosic fibre-reinforced, cementitious composite. In this research, soil–cement masonry is the cementitious matrix and coconut fibre (coir) the natural fibre. In the case study context, this cementitious composite is highly susceptible to physical damage due to intense rainfall and chemical deterioration that can be linked to the hydration of cement. The use of natural fibres, such as coir, compounds this problem. For the research to adequately address durability concern problems, accurate empirical data quantifying the damage to the natural fibre-reinforced cementitious composite are required. The discussion identifies the key knowledge gaps. It also describes the methodology adopted to produce and test the cementitious bricks investigated in the research. In addition to summarizing the main physical and mechanical properties, the findings presented in this article also (i) establish the bricks' resistance to wind-driven rain erosion and (ii) characterize the performance of the units on the basis of hydration-triggered chemical deterioration that can be expected in cement-stabilized earthen bricks. The article ends with a discussion of the key findings and a description of further research activities.

ACS Style

Esther Obonyo. Developing enhanced, lignocellulosic fibre reinforcement for low-cost, cementitious, construction materials. Architectural Engineering and Design Management 2012, 8, 30 -41.

AMA Style

Esther Obonyo. Developing enhanced, lignocellulosic fibre reinforcement for low-cost, cementitious, construction materials. Architectural Engineering and Design Management. 2012; 8 (1):30-41.

Chicago/Turabian Style

Esther Obonyo. 2012. "Developing enhanced, lignocellulosic fibre reinforcement for low-cost, cementitious, construction materials." Architectural Engineering and Design Management 8, no. 1: 30-41.

Proceedings article
Published: 16 June 2011 in Computing in Civil Engineering (2011)
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The ability to accurately determine the loading attributes of a truck (namely the axle configuration, the spacing between the axles, and the load imposed by each axle) while it is in motion is an important function for the design and structural health monitoring of bridges, and highways. Truck weigh-in-motion (WIM) as it is termed is an inverse problem where the load is identified from the observed response of the structure over which it is travelling. The problem has been reasonably well solved using neural network techniques, but there is still significant room for improvement in terms of reducing the number of misclassifications of trucks and increasing the precision of the axle spacing and load estimates. The problem can be formulated as an optimization problem. Genetic algorithms (GAs) are proven robust and efficient search optimization techniques. The potential of the GA approach for reverse identification of axle configuration and loading from bridge girder stress envelopes has been investigated and compared to an existing neural network solution. The investigation is a pilot study that considers a simply supported steel girder bridge with a concrete deck. The bending stresses of the bridge are simulated numerically and are used as the input for reverse modeling. The identification procedure is carried out using GAs by minimizing error between the measured bridge response and reconstructed bridge response. The performance of the GA depends on the tuning of genetic operators, hence different operator settings are considered and tuned for optimality. Advance strategies such as migration and multiple species with real coded representation variables are adopted to improve the performance. The effect of measurement parameters such as sampling frequency (50–400 Hz), levels of noise (5–25%), time varying load and measuring sections on accuracy of identification are also investigated. The performance of the GA approach is found to outperform the existing neural network solution. The significance of this is that, unlike the neural network approach, the GA solution can be applied to any bridge configuration for which a reasonable stress model exists. Moreover, the computational time for the GA is found to be on average 3–4 seconds which, although is several orders of magnitude slower than the neural network solution, it is well within what could be considered an acceptable delay for generating a solution.

ACS Style

G. Vala; I. Flood; E. Obonyo. Truck Weigh-in-Motion Using Reverse Modeling and Genetic Algorithms. Computing in Civil Engineering (2011) 2011, 219 -226.

AMA Style

G. Vala, I. Flood, E. Obonyo. Truck Weigh-in-Motion Using Reverse Modeling and Genetic Algorithms. Computing in Civil Engineering (2011). 2011; ():219-226.

Chicago/Turabian Style

G. Vala; I. Flood; E. Obonyo. 2011. "Truck Weigh-in-Motion Using Reverse Modeling and Genetic Algorithms." Computing in Civil Engineering (2011) , no. : 219-226.

Communication
Published: 30 March 2011 in Sustainability
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The paper is based on findings from research that assesses the potential for enhancing the performance of compressed earth bricks. A set of experiments was carried out to assess the potential for enhancing the bricks’ physical, mechanical and hygrothermal performance through the design of an optimal stabilization strategy. Three different types of bricks were fabricated: soil-cement, soil-cement-lime, and soil-cement-fiber. The different types of bricks did not exhibit significant differences in performances when assessed on the basis of porosity, density, water absorption, and compressive strength. However, upon exposure to elevated moisture and temperature conditions, the soil-cement-fiber bricks had the highest residual strength (87%). The soil-cement and soil-cement-lime bricks had residual strength values of 48.19 and 46.20% respectively. These results suggest that, like any other cement-based material, compressed earth brick properties are affected by hydration-triggered chemical and structural changes occurring in the matrix that would be difficult to isolate using tests that focus on “bulk” changes. The discussion in this paper presents findings from a research effort directed at quantifying the specific changes through an analysis of the microstructure.

ACS Style

Esther Obonyo. Optimizing the Physical, Mechanical and Hygrothermal Performance of Compressed Earth Bricks. Sustainability 2011, 3, 596 -604.

AMA Style

Esther Obonyo. Optimizing the Physical, Mechanical and Hygrothermal Performance of Compressed Earth Bricks. Sustainability. 2011; 3 (4):596-604.

Chicago/Turabian Style

Esther Obonyo. 2011. "Optimizing the Physical, Mechanical and Hygrothermal Performance of Compressed Earth Bricks." Sustainability 3, no. 4: 596-604.

Review
Published: 16 February 2011 in Sustainability
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Because of concerns over the construction industry‘s heavy use of cement and the general dissatisfaction with the performance of building envelopes with respect to durability, there is a growing demand for a novel class of ―green‖ binders. Geopolymer binders have re-emerged as binders that can be used as a replacement for Portland cement given their numerous advantages over the latter including lower carbon dioxide emissions, greater chemical and thermal resistance, combined with enhanced mechanical properties at both normal and extreme exposure conditions. The paper focuses on the use of geopolymer binders in building applications. It discusses the various options for starting materials and describes key engineering properties associated with geopolymer compositions that are ideal for structural applications. Specific properties, such as compressive strength, density, pore size distribution, cumulative water absorption, and acid resistance, are comparable to the specifications for structures incorporating conventional binders. This paper presents geopolymer binders, with their three dimensional microstructure, as material for structural elements that can be used to advance the realization of sustainable building systems.

ACS Style

Esther Obonyo; Elie Kamseu; Uphie C. Melo; Cristina Leonelli. Advancing the Use of Secondary Inputs in Geopolymer Binders for Sustainable Cementitious Composites: A Review. Sustainability 2011, 3, 410 -423.

AMA Style

Esther Obonyo, Elie Kamseu, Uphie C. Melo, Cristina Leonelli. Advancing the Use of Secondary Inputs in Geopolymer Binders for Sustainable Cementitious Composites: A Review. Sustainability. 2011; 3 (2):410-423.

Chicago/Turabian Style

Esther Obonyo; Elie Kamseu; Uphie C. Melo; Cristina Leonelli. 2011. "Advancing the Use of Secondary Inputs in Geopolymer Binders for Sustainable Cementitious Composites: A Review." Sustainability 3, no. 2: 410-423.

Communication
Published: 25 November 2010 in Sustainability
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The discussion in this paper is part of research directed at establishing optimal stabilization strategy for compressed bricks. The deployment context for the use of the compressed bricks was Dar es Salaam (Tanzania) where manually fabricated bricks are increasingly being used in low cost housing units. This discussion specifically focuses on strategies that can be used to counter deterioration due to wind-driven rain erosion. The impact of using cement, lime, fiber and a commercial stabilizing fluid was assessed. Factory-produced bricks were used for benchmarking. The durability of the bricks was assessed using the “modified” Bulletin 5 Spray Test. The different brick specimens were sprayed with water at 2.07 MPa and 4.14 MPa over one-hour time period while measuring the depth of erosion every 15 minutes. Factory-produced bricks hardly eroded at both 2.07 MPa and 4.14 MPa pressure levels. The maximum depth of erosion for Soil-Cement bricks ranged from a maximum of 0.5 mm at 2.07 MPa water pressure to 0.8 mm at 4.14 MPa. The maximum and minimum depths of erosion for Soil-Cement-Lime bricks were 25mm and 17 mm respectively. The inclusion of natural fiber in the bricks resulted in a sharp increase of the erosion depth to a maximum of 40 mm at 2.07 MPa and 55 mm at 4.14 Mpa. As the use of natural fibers and lime enhances some physio-mechanical properties, further research is necessary to determine ways of achieving this goal while maintaining acceptable levels of erosion resistance.

ACS Style

Esther Obonyo; Joseph Exelbirt; Malarvizhi Baskaran. Durability of Compressed Earth Bricks: Assessing Erosion Resistance Using the Modified Spray Testing. Sustainability 2010, 2, 3639 -3649.

AMA Style

Esther Obonyo, Joseph Exelbirt, Malarvizhi Baskaran. Durability of Compressed Earth Bricks: Assessing Erosion Resistance Using the Modified Spray Testing. Sustainability. 2010; 2 (12):3639-3649.

Chicago/Turabian Style

Esther Obonyo; Joseph Exelbirt; Malarvizhi Baskaran. 2010. "Durability of Compressed Earth Bricks: Assessing Erosion Resistance Using the Modified Spray Testing." Sustainability 2, no. 12: 3639-3649.