Solomon Sackey, PhD, A.M.ASCE | Kyungpook National University (original) (raw)

Papers by Solomon Sackey, PhD, A.M.ASCE

Research paper thumbnail of Duration Estimate at Completion: Improving Earned Value Management Forecasting Accuracy

KSCE Journal of Civil Engineering

Earned Value Management (EVM) has been established as a project management technique for project ... more Earned Value Management (EVM) has been established as a project management technique for project monitoring and control. The traditional EVM performs well in forecasting Cost Performance index and other cost metrics. However, in terms of schedule performance, the accuracy of the forecasted schedule metrics through the traditional EVM approach are always questionable. The schedule performance is not measured in time unit but rather in monetary units or uses cost information, which may cause misleading in the interpretation of the EVM schedule metrics. The schedule performance is not accurately forecasted, resulting in underestimating the estimate at completion (t). Even the renowned Earned Schedule also uses cost as a proxy to determine the earned schedule. This paper presents a new EVM tool, Duration estimate at completion (DEAC-model) developed to accurately forecast the time estimate at completion. DEAC-model uses the actual time spent on each activity, either in progress or upon completion, where the Performance is measured in time units. The benefits of DEAC-model to project management team and researchers are that it can be used: 1) to forecast schedule metrics accurately so that resources can be effectively allocated to complete the remaining activities, 2) as a gauge to assess if the project can be completed within the plan schedule, and 3) to apply time series and simple linear regression model concepts using excel worksheet syntax to forecast duration estimate at completion that is easily applicable.

Research paper thumbnail of Schedule Risk Analysis using a Proposed Modified Variance and Mean of the Original Program Evaluation and Review Technique Model

KSCE Journal of Civil Engineering

Research paper thumbnail of Development of an Expert System Tool for the Selection of Procurement System in Large-Scale Construction Projects (ESCONPROCS)

KSCE Journal of Civil Engineering

Research paper thumbnail of Environmental and Economic Performance of Asphalt Shingle and Clay Tile Roofing Sheets Using Life Cycle Assessment Approach and TOPSIS

Journal of Construction Engineering and Management

Research paper thumbnail of Life Cycle Assessment for the Production Phase of Nano-Silica-Modified Asphalt Mixtures

Applied Sciences

To combat the rutting effect and other distresses in asphalt concrete pavement, certain modifiers... more To combat the rutting effect and other distresses in asphalt concrete pavement, certain modifiers and additives have been developed to modify the asphalt mixture to improve its performance. Although few additives exist, nanomaterials have recently attracted significant attention from the pavement industry. Several experimental studies have shown that the use of nanomaterials to modify asphalt binder results in an improved oxidative aging property, increased resistance to the rutting effect, and improves the rheological properties of the asphalt mixture. However, despite the numerous benefits of using nanomaterials in asphalt binders and materials, there are various uncertainties regarding the environmental impacts of nano-modified asphalt mixtures (NMAM). Therefore, this study assessed a Nano-Silica-Modified Asphalt Mixtures in terms of materials production emissions through the Life Cycle Assessment methodology (LCA), and the results were compared to a conventional asphalt mixture ...

Research paper thumbnail of IOP Conference Series: Earth and Environmental Science

The refrigeration system is one of the most important systems in industry. Developers are constan... more The refrigeration system is one of the most important systems in industry. Developers are constantly seeking for how to avoid the damage to the environment. Magnetic refrigeration is an emerging, environment-friendly technology based on a magnetic solid that acts as a refrigerant by magneto-caloric effect (MCE). In the case of ferromagnetic materials, MCE warms as the magnetic moments of the atom are aligned by the application of a magnetic field. There are two types of magnetic phase changes that may occur at the Curie point: first order magnetic transition (FOMT) and second order magnetic transition (SOMT). The reference cycle for magnetic refrigeration is AMR (Active Magnetic Regenerative cycle), where the magnetic material matrix works both as a refrigerating medium and as a heat regenerating medium, while the fluid flowing in the porous matrix works as a heat transfer medium. Regeneration can be accomplished by blowing a heat transfer fluid in a reciprocating fashion through the regenerator made of magnetocaloric material that is alternately magnetized and demagnetized. Many magnetic refrigeration prototypes with different designs and software models have been built in different parts of the world. In this paper, the authors try to shed light on the magnetic refrigeration and show its effectiveness compared with conventional refrigeration methods.

Research paper thumbnail of IOP Conference Series: Earth and Environmental Science

The refrigeration system is one of the most important systems in industry. Developers are constan... more The refrigeration system is one of the most important systems in industry. Developers are constantly seeking for how to avoid the damage to the environment. Magnetic refrigeration is an emerging, environment-friendly technology based on a magnetic solid that acts as a refrigerant by magneto-caloric effect (MCE). In the case of ferromagnetic materials, MCE warms as the magnetic moments of the atom are aligned by the application of a magnetic field. There are two types of magnetic phase changes that may occur at the Curie point: first order magnetic transition (FOMT) and second order magnetic transition (SOMT). The reference cycle for magnetic refrigeration is AMR (Active Magnetic Regenerative cycle), where the magnetic material matrix works both as a refrigerating medium and as a heat regenerating medium, while the fluid flowing in the porous matrix works as a heat transfer medium. Regeneration can be accomplished by blowing a heat transfer fluid in a reciprocating fashion through the regenerator made of magnetocaloric material that is alternately magnetized and demagnetized. Many magnetic refrigeration prototypes with different designs and software models have been built in different parts of the world. In this paper, the authors try to shed light on the magnetic refrigeration and show its effectiveness compared with conventional refrigeration methods.

Research paper thumbnail of Duration Estimate at Completion: Improving Earned Value Management Forecasting Accuracy

KSCE Journal of Civil Engineering, 2020

Earned Value Management (EVM) has been established as a project management technique for project ... more Earned Value Management (EVM) has been established as a project management technique for project monitoring and control. The traditional EVM performs well in forecasting Cost Performance index and other cost metrics. However, in terms of schedule performance, the accuracy of the forecasted schedule metrics through the traditional EVM approach are always questionable. The schedule performance is not measured in time unit but rather in monetary units or uses cost information, which may cause misleading in the interpretation of the EVM schedule metrics. The schedule performance is not accurately forecasted, resulting in underestimating the estimate at completion (t). Even the renowned Earned Schedule also uses cost as a proxy to determine the earned schedule. This paper presents a new EVM tool, Duration estimate at completion (DEAC-model) developed to accurately forecast the time estimate at completion. DEAC-model uses the actual time spent on each activity, either in progress or upon completion, where the Performance is measured in time units. The benefits of DEAC-model to project management team and researchers are that it can be used: 1) to forecast schedule metrics accurately so that resources can be effectively allocated to complete the remaining activities, 2) as a gauge to assess if the project can be completed within the plan schedule, and 3) to apply time series and simple linear regression model concepts using excel worksheet syntax to forecast duration estimate at completion that is easily applicable

Research paper thumbnail of Life Cycle Assessment for the Production Phase of Nano-Silica-Modified Asphalt Mixtures

Applied Sciences Journal, 2019

Featured Application: The application of LCA to NMAM has the potential to guide decision-makers o... more Featured Application: The application of LCA to NMAM has the potential to guide decision-makers on the selection of pavement modification additives to realize the benefits of using nanomaterials in pavements while avoiding potential environmental risks.
Abstract: To combat the rutting effect and other distresses in asphalt concrete pavement, certain modifiers and additives have been developed to modify the asphalt mixture to improve its performance. Although few additives exist, nanomaterials have recently attracted significant attention from the pavement industry. Several experimental studies have shown that the use of nanomaterials to modify asphalt binder results in an improved oxidative aging property, increased resistance to the rutting effect, and improves the rheological properties of the asphalt mixture. However, despite the numerous benefits of using nanomaterials in asphalt binders and materials, there are various uncertainties regarding the environmental impacts of nano-modified asphalt mixtures (NMAM). Therefore, this study assessed a Nano-Silica-Modified Asphalt Mixtures in terms of materials production emissions through the Life Cycle Assessment methodology (LCA), and the results were compared to a conventional asphalt mixture to understand the impact contribution of nano-silica in asphalt mixtures. To be able to compare the relative significance of each impact category, the normalized score for each impact category was calculated using the impact scores and the normalization factors. The results showed that NMAM had a global warming potential of 7.44563 × 10 3 kg CO 2-Eq per functional unit (FU) compared to 7.41900 × 10 3 kg CO 2-Eq per functional unit of the conventional asphalt mixture. The application of LCA to NMAM has the potential to guide decision-makers on the selection of pavement modification additives to realize the benefits of using nanomaterials in pavements while avoiding potential environmental risks.

Research paper thumbnail of Heuristic-based multiobjective time-cost optimization problem considering risk and uncertainty impact

Australian Journal of Science and Technology, 2019

It is the goal of project planners to complete a project at a minimal time and cost. Additional d... more It is the goal of project planners to complete a project at a minimal time and cost. Additional demand for resources which result in increased cost is required to complete the project within a shorter time period. This problem of time-cost trade-off (TCT) has led to several studies conducted to find an optimal solution using different optimization techniques such as the heuristic method and other optimization techniques. However, in these studies using the heuristic method, the researchers mainly use deterministic activity durations to model the TCT problem. TCT analysis using deterministic durations will only produce deceiving results which are unrealistic. With activity durations likely to deviate from actual durations, this study presents a heuristic-based approach for time-cost optimization by taking into account the impact of risk and uncertainty of activity duration. This was done using a probabilistic approach through simulation to develop realistic durations and use these durations as input to reschedule the critical path method network. A numerical example problem was applied and the results were compared to existing studies to understand the impact of risk and uncertainty on TCT analysis. This approach will guide decision-makers in making efficient and effective decisions in TCT optimization problems.

Research paper thumbnail of Schedule Risk Analysis using a Proposed Modified Variance and Mean of the Original Program Evaluation and Review Technique Model

KSCE Journal of Civil Engineering, 2019

The Program Evaluation and Review Technique (PERT) model uses parameters such as the specified pr... more The Program Evaluation and Review Technique (PERT) model uses parameters such as the specified project completion time, mean, and variance to estimate the probability of project completion time. However, this model uses a weighted average and unweighted value in the variance, which is based on six sigma of the mean. Despite many proposed modifications to improve the traditional PERT model, the hidden error in the calculation of the variance and mean of the PERT approach has not been adequately addressed. This error leads to underestimation of the schedule risk. Considering the impact of variance and mean on the probability of project completion times, this study contributes to the improvement of the accuracy of schedule risk estimation by proposing a modified variance and mean of the original PERT model. The original PERT model was first used to estimate the project completion time. However, using the proposed modified model to estimate the completion time, a 95% confidence interval assumption and the corresponding distribution within ±2 standard deviation of the mean and standard or Z values were employed to model the new mean and variance equations. To prove the validity of the proposed modified variance and mean assumptions, we performed a schedule risk analysis through simulation using Oracle Crystal Ball for comparison. The results showed that the proposed PERT model had a better mean error rate of 2.46% as compared to 3.31% of the original PERT model.

Research paper thumbnail of Environmental and Economic Performance of Asphalt Shingle and Clay Tile Roofing Sheets Using Life Cycle Assessment Approach and TOPSIS

The construction industry utilizes many materials that go through different manufacturing and tra... more The construction industry utilizes many materials that go through different manufacturing and transportation processes. Selecting and using environmentally friendly or green building materials is one way to reduce the inimical environmental effects associated with the construction industry. However, environmental preference cannot be used as the only criterion in selecting a building material. As cost is an important factor, environmental performance needs to be balanced against the economic performance. The decisions on material selection, therefore, need improvement. This study analyzed and compared the environmental and economic performance of asphalt shingle and clay tile roofing materials using the building for environmental and economic sustainability (BEES) model. The results were then used to develop a combined performance score using the technique for order preference by similarity to ideal solution (TOPSIS) to assist decisions pertaining to the selection of the best material based on the performance score. To present another decision criteria to compare and select a roof material, the study utilized the contingent valuation method (CVM) to estimate the environmental cost associated with these alternative materials. The simulation results showed that clay tile had a better environmental performance score of 0.3525 points ðptsÞ=unit compared to the score of 0.4135 pts=unit for asphalt shingles; however, asphalt shingles had a better overall performance score of 0.5985 pts against 0.4153 pts for the clay tile. Merging environmental and economic considerations to a common score as presented in this study will help improve and contribute to the quality of decision making in that it provides a substantial basis to select the most suitable, cost-effective roofing material.

Research paper thumbnail of Development of an Expert System tool for the selection of Procurement System in Large- Scale Construction Projects. (ESCONPROCS)

The human knowledge of a specific domain is dissipated either in books and journals or exists in ... more The human knowledge of a specific domain is dissipated either in books and journals or exists in the minds of few human experts. Expert system technology, which is of late becoming an important tool, uses the power of the human brain to store knowledge electronically so that information regarding decision-making can easily be accessed at anywhere and at any time. More often than not most decisions in the industry are based on just subjective decisions. But since each project is different from the other, there is the need to integrate heuristic approach in other to arrive at better decisions. Therefore the system, ESCONPROCS (Expert system for construction procurement selection) which is an expert system tool was developed based on extensive literature review of the available procurement systems as well as clients' priorities and other external factors that influence the selection of an appropriate procurement system. An expert survey was conducted and their responses were used to provide a recommendation for the rules. The system, ESCONPROCS is developed to assist decision-maker (client) reaches a more informed decision on procurement system selection and contracting.

Conference Presentations by Solomon Sackey, PhD, A.M.ASCE

Research paper thumbnail of IOP Conference Series: Earth and Environmental Science The Environmental Load Characteristic Analysis of LCA-based IPC Girder Bridge

The carbon emission amount of the Republic of Korea ranks 8th in the world including... more The carbon emission amount of the Republic of Korea ranks 8th in the world including China and the US and accordingly, the government announced its emission reduction plan by 37% compared to BAU (8.51 million tons) by 2030. As a result of the emission trading scheme that has been implemented since 2015, efforts are being made to reduce environmental load. Accordingly, this study analyzed the material-specific environmental load distribution and environmental impact category for 60 IPC girder bridges of national road constructions in
Korea by utilizing the life cycle assessment (LCA) method. The analysis result was found to be in the order of ready-mixed concrete (RMC) (64.00%), rebar (9.1%), timber (7.8%) and plywood (5.6%). As for environmental impact category-specific result, it was found to be in the order of global warming (50.60%), abiotic resource depletion (32.20%), photochemical oxidant creation (POC) (10.10%) and human toxicity (HT) (7.10%), thereby considered to be helpful when selecting the form of bridge while considering environmental load during the planning and design phases

Research paper thumbnail of Duration Estimate at Completion: Improving Earned Value Management Forecasting Accuracy

KSCE Journal of Civil Engineering

Earned Value Management (EVM) has been established as a project management technique for project ... more Earned Value Management (EVM) has been established as a project management technique for project monitoring and control. The traditional EVM performs well in forecasting Cost Performance index and other cost metrics. However, in terms of schedule performance, the accuracy of the forecasted schedule metrics through the traditional EVM approach are always questionable. The schedule performance is not measured in time unit but rather in monetary units or uses cost information, which may cause misleading in the interpretation of the EVM schedule metrics. The schedule performance is not accurately forecasted, resulting in underestimating the estimate at completion (t). Even the renowned Earned Schedule also uses cost as a proxy to determine the earned schedule. This paper presents a new EVM tool, Duration estimate at completion (DEAC-model) developed to accurately forecast the time estimate at completion. DEAC-model uses the actual time spent on each activity, either in progress or upon completion, where the Performance is measured in time units. The benefits of DEAC-model to project management team and researchers are that it can be used: 1) to forecast schedule metrics accurately so that resources can be effectively allocated to complete the remaining activities, 2) as a gauge to assess if the project can be completed within the plan schedule, and 3) to apply time series and simple linear regression model concepts using excel worksheet syntax to forecast duration estimate at completion that is easily applicable.

Research paper thumbnail of Schedule Risk Analysis using a Proposed Modified Variance and Mean of the Original Program Evaluation and Review Technique Model

KSCE Journal of Civil Engineering

Research paper thumbnail of Development of an Expert System Tool for the Selection of Procurement System in Large-Scale Construction Projects (ESCONPROCS)

KSCE Journal of Civil Engineering

Research paper thumbnail of Environmental and Economic Performance of Asphalt Shingle and Clay Tile Roofing Sheets Using Life Cycle Assessment Approach and TOPSIS

Journal of Construction Engineering and Management

Research paper thumbnail of Life Cycle Assessment for the Production Phase of Nano-Silica-Modified Asphalt Mixtures

Applied Sciences

To combat the rutting effect and other distresses in asphalt concrete pavement, certain modifiers... more To combat the rutting effect and other distresses in asphalt concrete pavement, certain modifiers and additives have been developed to modify the asphalt mixture to improve its performance. Although few additives exist, nanomaterials have recently attracted significant attention from the pavement industry. Several experimental studies have shown that the use of nanomaterials to modify asphalt binder results in an improved oxidative aging property, increased resistance to the rutting effect, and improves the rheological properties of the asphalt mixture. However, despite the numerous benefits of using nanomaterials in asphalt binders and materials, there are various uncertainties regarding the environmental impacts of nano-modified asphalt mixtures (NMAM). Therefore, this study assessed a Nano-Silica-Modified Asphalt Mixtures in terms of materials production emissions through the Life Cycle Assessment methodology (LCA), and the results were compared to a conventional asphalt mixture ...

Research paper thumbnail of IOP Conference Series: Earth and Environmental Science

The refrigeration system is one of the most important systems in industry. Developers are constan... more The refrigeration system is one of the most important systems in industry. Developers are constantly seeking for how to avoid the damage to the environment. Magnetic refrigeration is an emerging, environment-friendly technology based on a magnetic solid that acts as a refrigerant by magneto-caloric effect (MCE). In the case of ferromagnetic materials, MCE warms as the magnetic moments of the atom are aligned by the application of a magnetic field. There are two types of magnetic phase changes that may occur at the Curie point: first order magnetic transition (FOMT) and second order magnetic transition (SOMT). The reference cycle for magnetic refrigeration is AMR (Active Magnetic Regenerative cycle), where the magnetic material matrix works both as a refrigerating medium and as a heat regenerating medium, while the fluid flowing in the porous matrix works as a heat transfer medium. Regeneration can be accomplished by blowing a heat transfer fluid in a reciprocating fashion through the regenerator made of magnetocaloric material that is alternately magnetized and demagnetized. Many magnetic refrigeration prototypes with different designs and software models have been built in different parts of the world. In this paper, the authors try to shed light on the magnetic refrigeration and show its effectiveness compared with conventional refrigeration methods.

Research paper thumbnail of IOP Conference Series: Earth and Environmental Science

The refrigeration system is one of the most important systems in industry. Developers are constan... more The refrigeration system is one of the most important systems in industry. Developers are constantly seeking for how to avoid the damage to the environment. Magnetic refrigeration is an emerging, environment-friendly technology based on a magnetic solid that acts as a refrigerant by magneto-caloric effect (MCE). In the case of ferromagnetic materials, MCE warms as the magnetic moments of the atom are aligned by the application of a magnetic field. There are two types of magnetic phase changes that may occur at the Curie point: first order magnetic transition (FOMT) and second order magnetic transition (SOMT). The reference cycle for magnetic refrigeration is AMR (Active Magnetic Regenerative cycle), where the magnetic material matrix works both as a refrigerating medium and as a heat regenerating medium, while the fluid flowing in the porous matrix works as a heat transfer medium. Regeneration can be accomplished by blowing a heat transfer fluid in a reciprocating fashion through the regenerator made of magnetocaloric material that is alternately magnetized and demagnetized. Many magnetic refrigeration prototypes with different designs and software models have been built in different parts of the world. In this paper, the authors try to shed light on the magnetic refrigeration and show its effectiveness compared with conventional refrigeration methods.

Research paper thumbnail of Duration Estimate at Completion: Improving Earned Value Management Forecasting Accuracy

KSCE Journal of Civil Engineering, 2020

Earned Value Management (EVM) has been established as a project management technique for project ... more Earned Value Management (EVM) has been established as a project management technique for project monitoring and control. The traditional EVM performs well in forecasting Cost Performance index and other cost metrics. However, in terms of schedule performance, the accuracy of the forecasted schedule metrics through the traditional EVM approach are always questionable. The schedule performance is not measured in time unit but rather in monetary units or uses cost information, which may cause misleading in the interpretation of the EVM schedule metrics. The schedule performance is not accurately forecasted, resulting in underestimating the estimate at completion (t). Even the renowned Earned Schedule also uses cost as a proxy to determine the earned schedule. This paper presents a new EVM tool, Duration estimate at completion (DEAC-model) developed to accurately forecast the time estimate at completion. DEAC-model uses the actual time spent on each activity, either in progress or upon completion, where the Performance is measured in time units. The benefits of DEAC-model to project management team and researchers are that it can be used: 1) to forecast schedule metrics accurately so that resources can be effectively allocated to complete the remaining activities, 2) as a gauge to assess if the project can be completed within the plan schedule, and 3) to apply time series and simple linear regression model concepts using excel worksheet syntax to forecast duration estimate at completion that is easily applicable

Research paper thumbnail of Life Cycle Assessment for the Production Phase of Nano-Silica-Modified Asphalt Mixtures

Applied Sciences Journal, 2019

Featured Application: The application of LCA to NMAM has the potential to guide decision-makers o... more Featured Application: The application of LCA to NMAM has the potential to guide decision-makers on the selection of pavement modification additives to realize the benefits of using nanomaterials in pavements while avoiding potential environmental risks.
Abstract: To combat the rutting effect and other distresses in asphalt concrete pavement, certain modifiers and additives have been developed to modify the asphalt mixture to improve its performance. Although few additives exist, nanomaterials have recently attracted significant attention from the pavement industry. Several experimental studies have shown that the use of nanomaterials to modify asphalt binder results in an improved oxidative aging property, increased resistance to the rutting effect, and improves the rheological properties of the asphalt mixture. However, despite the numerous benefits of using nanomaterials in asphalt binders and materials, there are various uncertainties regarding the environmental impacts of nano-modified asphalt mixtures (NMAM). Therefore, this study assessed a Nano-Silica-Modified Asphalt Mixtures in terms of materials production emissions through the Life Cycle Assessment methodology (LCA), and the results were compared to a conventional asphalt mixture to understand the impact contribution of nano-silica in asphalt mixtures. To be able to compare the relative significance of each impact category, the normalized score for each impact category was calculated using the impact scores and the normalization factors. The results showed that NMAM had a global warming potential of 7.44563 × 10 3 kg CO 2-Eq per functional unit (FU) compared to 7.41900 × 10 3 kg CO 2-Eq per functional unit of the conventional asphalt mixture. The application of LCA to NMAM has the potential to guide decision-makers on the selection of pavement modification additives to realize the benefits of using nanomaterials in pavements while avoiding potential environmental risks.

Research paper thumbnail of Heuristic-based multiobjective time-cost optimization problem considering risk and uncertainty impact

Australian Journal of Science and Technology, 2019

It is the goal of project planners to complete a project at a minimal time and cost. Additional d... more It is the goal of project planners to complete a project at a minimal time and cost. Additional demand for resources which result in increased cost is required to complete the project within a shorter time period. This problem of time-cost trade-off (TCT) has led to several studies conducted to find an optimal solution using different optimization techniques such as the heuristic method and other optimization techniques. However, in these studies using the heuristic method, the researchers mainly use deterministic activity durations to model the TCT problem. TCT analysis using deterministic durations will only produce deceiving results which are unrealistic. With activity durations likely to deviate from actual durations, this study presents a heuristic-based approach for time-cost optimization by taking into account the impact of risk and uncertainty of activity duration. This was done using a probabilistic approach through simulation to develop realistic durations and use these durations as input to reschedule the critical path method network. A numerical example problem was applied and the results were compared to existing studies to understand the impact of risk and uncertainty on TCT analysis. This approach will guide decision-makers in making efficient and effective decisions in TCT optimization problems.

Research paper thumbnail of Schedule Risk Analysis using a Proposed Modified Variance and Mean of the Original Program Evaluation and Review Technique Model

KSCE Journal of Civil Engineering, 2019

The Program Evaluation and Review Technique (PERT) model uses parameters such as the specified pr... more The Program Evaluation and Review Technique (PERT) model uses parameters such as the specified project completion time, mean, and variance to estimate the probability of project completion time. However, this model uses a weighted average and unweighted value in the variance, which is based on six sigma of the mean. Despite many proposed modifications to improve the traditional PERT model, the hidden error in the calculation of the variance and mean of the PERT approach has not been adequately addressed. This error leads to underestimation of the schedule risk. Considering the impact of variance and mean on the probability of project completion times, this study contributes to the improvement of the accuracy of schedule risk estimation by proposing a modified variance and mean of the original PERT model. The original PERT model was first used to estimate the project completion time. However, using the proposed modified model to estimate the completion time, a 95% confidence interval assumption and the corresponding distribution within ±2 standard deviation of the mean and standard or Z values were employed to model the new mean and variance equations. To prove the validity of the proposed modified variance and mean assumptions, we performed a schedule risk analysis through simulation using Oracle Crystal Ball for comparison. The results showed that the proposed PERT model had a better mean error rate of 2.46% as compared to 3.31% of the original PERT model.

Research paper thumbnail of Environmental and Economic Performance of Asphalt Shingle and Clay Tile Roofing Sheets Using Life Cycle Assessment Approach and TOPSIS

The construction industry utilizes many materials that go through different manufacturing and tra... more The construction industry utilizes many materials that go through different manufacturing and transportation processes. Selecting and using environmentally friendly or green building materials is one way to reduce the inimical environmental effects associated with the construction industry. However, environmental preference cannot be used as the only criterion in selecting a building material. As cost is an important factor, environmental performance needs to be balanced against the economic performance. The decisions on material selection, therefore, need improvement. This study analyzed and compared the environmental and economic performance of asphalt shingle and clay tile roofing materials using the building for environmental and economic sustainability (BEES) model. The results were then used to develop a combined performance score using the technique for order preference by similarity to ideal solution (TOPSIS) to assist decisions pertaining to the selection of the best material based on the performance score. To present another decision criteria to compare and select a roof material, the study utilized the contingent valuation method (CVM) to estimate the environmental cost associated with these alternative materials. The simulation results showed that clay tile had a better environmental performance score of 0.3525 points ðptsÞ=unit compared to the score of 0.4135 pts=unit for asphalt shingles; however, asphalt shingles had a better overall performance score of 0.5985 pts against 0.4153 pts for the clay tile. Merging environmental and economic considerations to a common score as presented in this study will help improve and contribute to the quality of decision making in that it provides a substantial basis to select the most suitable, cost-effective roofing material.

Research paper thumbnail of Development of an Expert System tool for the selection of Procurement System in Large- Scale Construction Projects. (ESCONPROCS)

The human knowledge of a specific domain is dissipated either in books and journals or exists in ... more The human knowledge of a specific domain is dissipated either in books and journals or exists in the minds of few human experts. Expert system technology, which is of late becoming an important tool, uses the power of the human brain to store knowledge electronically so that information regarding decision-making can easily be accessed at anywhere and at any time. More often than not most decisions in the industry are based on just subjective decisions. But since each project is different from the other, there is the need to integrate heuristic approach in other to arrive at better decisions. Therefore the system, ESCONPROCS (Expert system for construction procurement selection) which is an expert system tool was developed based on extensive literature review of the available procurement systems as well as clients' priorities and other external factors that influence the selection of an appropriate procurement system. An expert survey was conducted and their responses were used to provide a recommendation for the rules. The system, ESCONPROCS is developed to assist decision-maker (client) reaches a more informed decision on procurement system selection and contracting.

Research paper thumbnail of IOP Conference Series: Earth and Environmental Science The Environmental Load Characteristic Analysis of LCA-based IPC Girder Bridge

The carbon emission amount of the Republic of Korea ranks 8th in the world including... more The carbon emission amount of the Republic of Korea ranks 8th in the world including China and the US and accordingly, the government announced its emission reduction plan by 37% compared to BAU (8.51 million tons) by 2030. As a result of the emission trading scheme that has been implemented since 2015, efforts are being made to reduce environmental load. Accordingly, this study analyzed the material-specific environmental load distribution and environmental impact category for 60 IPC girder bridges of national road constructions in
Korea by utilizing the life cycle assessment (LCA) method. The analysis result was found to be in the order of ready-mixed concrete (RMC) (64.00%), rebar (9.1%), timber (7.8%) and plywood (5.6%). As for environmental impact category-specific result, it was found to be in the order of global warming (50.60%), abiotic resource depletion (32.20%), photochemical oxidant creation (POC) (10.10%) and human toxicity (HT) (7.10%), thereby considered to be helpful when selecting the form of bridge while considering environmental load during the planning and design phases