Papers by Waleed Mahfouz M. A. Youssef
The construction project management is about quality, timely, and costly managing construction in... more The construction project management is about quality, timely, and costly managing construction inputs and outputs. However, its achievement continues to present a major challenge to most large construction projects all over the world due to the high degrees of complexity and variability. For instance, delivery of construction projects has been adversely influenced by several drastic risks. A major and critical concern in the time scheduling process is the accurate determination of activities durations. This calls for a continuous improvement in the conventional techniques of estimating activity duration and in utilizing the deterministic scheduling. This thesis presents a comprehensive analysis of activities duration of construction projects in the Middle East countries. The analysis was carried out on twenty construction projects including more than 125,000 activities with a total budget of about fifteen billions Egyptian Pounds (EGP) and comprising all engineering, procurement and construction (EPC) activities. The thesis seeks to bridge the gap between theory and application and to utilize a probabilistic scheduling approach that yields reliable estimations of activity duration. The focus is to evaluate the actual behaviour of activities exposed to different types of risk and uncertainty and to derive regression models predicting activities’ durations categorized according to country, type of work, and to the Construction Specifications Institute (CSI) divisions. First, previous research on the causes of delay and the probabilistic analysis of activities in developing and developed countries has been compiled and critically reviewed. This review indicated that there is no generally accepted Probability Density Function (PDF) to represent the activity duration through the simulation process. However, Beta and Triangular distributions were the mostly used PDF’s. Then, activity and project durations of different projects such as hospitals, hotels, stadiums, highways, malls, and high rise buildings in Egypt, Kuwait, Saudi Arabia, UAE, Qatar and Oman were analysed. The analysis considered the estimated durations, the actual durations, and the budgets of the EPC activities. It also included the quantitative analysis of causes of delay on the performance of seven repetitive construction activities in a housing project that is composed of 1271 similar houses in Kuwait. Besides, statistical analysis and curve fitting of the estimated versus the actual durations of activities were conducted. In addition, the study developed predictive regression models to estimate the statistics of activities durations. Finally, a special program that uses the concluded PDF and regression models to predict the project’s overall durations at different levels of confidence was developed. It is found that the three most influencing risks on the time performance of construction activities in Kuwait are: (1) inadequate planning and time scheduling; (2) slow financial and payment procedures; and (3) fluctuation of productivity levels. In addition, it is found that the best PDF to represent activities in construction projects is the lognormal distribution, while the second best PDF is the gamma distribution. Besides, it is shown that the normal distribution has the lowest level of confidence. Furthermore, it is found that as the estimated duration decreases, the relative duration slippage increases. The ratio of the highest, actual activity duration to the corresponding mean duration is always more than 4 for projects in the Middle East, which differs from that suggested in previous studies (1.25). As a general rule, the forecasted project’s overall duration- based on the proposed regression models and utilizing lognormal distribution- tends to be greater than that calculated using conventionally estimated activities. Nevertheless, validation tests showed that the forecasted projects’ durations are good estimates of the real ones. Consequently, these forecasted projects’ durations could oblige contractors to implement different methodologies and alternative plans to reduce the project’s duration.
International Journal of BIM and Engineering Science, 2021
Currently, the world encounters the outbreak of an unprecedented epidemic named novel coronavirus... more Currently, the world encounters the outbreak of an unprecedented epidemic named novel coronavirus COVID -19. World Health Organization (WHO) advises maintaining social distancing, preserving personal hygiene, and staying informed with the latest guidelines. WHO also reports the patients with robust immunity can combat the virus. However, the workers in the construction industry work and live in a crowded and non-hygiene environment. Moreover, they are characterized by illiteracy, a dearth of awareness, and chronic health problems that prove weak immunity. Therefore, this study aims to find the relationship between the virus and the prevailing conditions and the environment of the construction industry, under focus, and study so that the construction industry is not a vulnerability gap that may exacerbate the crisis. An extensive literature exploration for the latest research deals with coronavirus, the construction industry ergonomics, and its relevant diseases. This study makes rob...
International Journal of Construction Engineering and Management, 2013
Construction projects' cost and degree of complexity are mounted rapidly in North Africa and Arab... more Construction projects' cost and degree of complexity are mounted rapidly in North Africa and Arabian Gulf Countries inducing higher potential levels of risks to costs and time overruns; therefore, greater attention must be directed to control both time and cost. The conventional techniques for estimating activity's duration and time scheduling have been proved themselves as unreliable techniques in front of growing construction projects' challenge. Simu lation techniques have been utilized to provide reliable solutions for risky construction project scheduling. Beta and Norma l Probability Density Functions (PDF) have been widely utilized in the past to represent the activities' duration included in simu lation process. This paper presents a statistical analysis for construction activities estimated and actual durations in North African and Arabian Gu lf countries. The analysis was carried out on twenty construction projects including more than 125,000 activities representing all engineering, p rocurement and construction (EPC) activ ities. The statistical analysis of results proved that the most appropriate PDF to rep resent the duration of activities is the Lognormal distribution followed by the Ga mma distribution. However, utilizing Beta o r Norma l PDF may be ut ilized at lower confidence level. The analysis man ifests that about 40% of the activit ies contribute to the delay of the whole pro ject.
International Journal of BIM and Engineering Science, 2021
Currently, the world encounters the outbreak of an unprecedented epidemic named novel coronavirus... more Currently, the world encounters the outbreak of an unprecedented epidemic named novel coronavirus COVID-19. World Health Organization (WHO) advises maintaining social distancing, preserving personal hygiene, and staying informed with the latest guidelines. WHO also reports the patients with robust immunity can combat the virus. However, the workers in the construction industry work and live in a crowded and non-hygiene environment. Moreover, they are characterized by illiteracy, a dearth of awareness, and chronic health problems that prove weak immunity. Therefore, this study aims to find the relationship between the virus and the prevailing conditions and the environment of the construction industry, under focus, and study so that the construction industry is not a vulnerability gap that may exacerbate the crisis. An extensive literature exploration for the latest research deals with coronavirus, the construction industry ergonomics, and its relevant diseases. This study makes robust alerts to motivate the governments, organizations, and individuals to collaborate to find solutions to close the gap between the current situation in the construction of ergonomics and the required precaution to avoid the outbreak of the virus. This study makes a crucial and novel contribution by paving the way for providing solutions to save humanity worldwide. The management system should review the conventional risk assessment procedures, and developed criteria must be introduced and become an everyday practice of all construction projects. This will help identify the gaps within the safety procedures associated with the COVID-19 protection aspects. This article also introduces a framework in this regard.
Construction Activities Duration Patterns in the Middle East, 2013
Construction projects' cost and degree of complexity are mounted rapidly in North Africa and Arab... more Construction projects' cost and degree of complexity are mounted rapidly in North Africa and Arabian Gulf Countries inducing higher potential levels of risks to costs and time overruns; therefore, greater attention must be directed to control both time and cost. The conventional techniques for estimating activity's duration and time scheduling have been proved themselves as unreliable techniques in front of growing construction projects' challenge. Simu lation techniques have been utilized to provide reliable solutions for risky construction project scheduling. Beta and Norma l Probability Density Functions (PDF) have been widely utilized in the past to represent the activities' duration included in simu lation process. This paper presents a statistical analysis for construction activities estimated and actual durations in North African and Arabian Gu lf countries. The analysis was carried out on twenty construction projects including more than 125,000 activities representing all engineering, p rocurement and construction (EPC) activ ities. The statistical analysis of results proved that the most appropriate PDF to rep resent the duration of activities is the Lognormal distribution followed by the Ga mma distribution. However, utilizing Beta o r Norma l PDF may be ut ilized at lower confidence level. The analysis man ifests that about 40% of the activit ies contribute to the delay of the whole pro ject.
PhD Thesis, Dec 1, 2014
The construction project management is about quality, timely, and costly managing construction in... more The construction project management is about quality, timely, and costly managing construction inputs and outputs. However, its achievement continues to present a major challenge to most large construction projects all over the world due to the high degrees of complexity and variability. For instance, delivery of construction projects has been adversely influenced by several drastic risks. A major and critical concern in the time scheduling process is the accurate determination of activities durations. This calls for a continuous improvement in the conventional techniques of estimating activity duration and in utilizing the deterministic scheduling.
This thesis presents a comprehensive analysis of activities duration of construction projects in the Middle East countries. The analysis was carried out on twenty construction projects including more than 125,000 activities with a total budget of about fifteen billions Egyptian Pounds (EGP) and comprising all engineering, procurement and construction (EPC) activities. The thesis seeks to bridge the gap between theory and application and to utilize a probabilistic scheduling approach that yields reliable estimations of activity duration. The focus is to evaluate the actual behaviour of activities exposed to different types of risk and uncertainty and to derive regression models predicting activities’ durations categorized according to country, type of work, and to the Construction Specifications Institute (CSI) divisions.
First, previous research on the causes of delay and the probabilistic analysis of activities in developing and developed countries has been compiled and critically reviewed. This review indicated that there is no generally accepted Probability Density Function (PDF) to represent the activity duration through the simulation process. However, Beta and Triangular distributions were the mostly used PDF’s.
Then, activity and project durations of different projects such as hospitals, hotels, stadiums, highways, malls, and high rise buildings in Egypt, Kuwait, Saudi Arabia, UAE, Qatar and Oman were analysed. The analysis considered the estimated durations, the actual durations, and the budgets of the EPC activities. It also included the quantitative analysis of causes of delay on the performance of seven repetitive construction activities in a housing project that is composed of 1271 similar houses in Kuwait. Besides, statistical analysis and curve fitting of the estimated versus the actual durations of activities were conducted. In addition, the study developed predictive regression models to estimate the statistics of activities durations. Finally, a special program that uses the concluded PDF and regression models to predict the project’s overall durations at different levels of confidence was developed.
It is found that the three most influencing risks on the time performance of construction activities in Kuwait are: (1) inadequate planning and time scheduling; (2) slow financial and payment procedures; and (3) fluctuation of productivity levels. In addition, it is found that the best PDF to represent activities in construction projects is the lognormal distribution, while the second best PDF is the gamma distribution. Besides, it is shown that the normal distribution has the lowest level of confidence. Furthermore, it is found that as the estimated duration decreases, the relative duration slippage increases. The ratio of the highest, actual activity duration to the corresponding mean duration is always more than 4 for projects in the Middle East, which differs from that suggested in previous studies (1.25). As a general rule, the forecasted project’s overall duration- based on the proposed regression models and utilizing lognormal distribution- tends to be greater than that calculated using conventionally estimated activities. Nevertheless, validation tests showed that the forecasted projects’ durations are good estimates of the real ones. Consequently, these forecasted projects’ durations could oblige contractors to implement different methodologies and alternative plans to reduce the project’s duration.
Thesis Chapters by Waleed Mahfouz M. A. Youssef
Spatial variability is one of the most significant characteristics of soil properties, even withi... more Spatial variability is one of the most significant characteristics of soil properties, even within homogeneous layers. The physical description of this spatial variation is unclear, due to the highly expensive sampling, uncontrollable measurement errors, and modeling uncertainty. While the deterministic approach failed to present a reasonable quantification for the spatial variability of soil properties, the probabilistic approach has been utilized to assess and quantify the effects of soil spatial variability on the behavior of some typical soil-structure systems.
This study investigates the effect of spatial variability of soil properties (mass density γs, coefficient of friction tanδ, angle of internal friction (φ), and wall mass density γc, on the factors of safety against sliding (Fs), and overturning (Fo), as well as the maximum bending moment (M) of cantilever retaining walls.
For risk assessment, soil properties are described using appropriate probabilistic models. Deterministic analysis combined with Monte Carlo Simulation (MCS) is employed to analyze both spatially fully correlated and spatially uncorrelated soil profiles.
A FORTRAN program is developed to: (1) generate random variables with both Gauassian and non-Gauassian probability density functions (PDF); (2) simulate possible probability distributions for distinct soil properties; (3) perform repetitive analysis for each set of variable PDFs to generate the population of Fs, Fo, and M; and (4) calculate the statistical parameters of Fs, Fo, and M. The program is then applied to conduct an extensive parametric study.
This parametric study is performed to quantify and assess the effects of model uncertainty and the effect of spatial heterogeneity of soil properties, utilizing two different soil profiles: (1) spatially fully correlated soil profile; and (2) spatially uncorrelated soil profile.
The numerical results show that the effects of spatial variability and uncertainty of input variables on wall safety vary from one variable to the other. Consequently, considerable care should be directed to those variables that have the greatest effects. For typical degrees of uncertainty, it is found that the structural risk is highest when the PDF of tanδ and φ is normal (Gauassian), or has an upper triangular shape (non-Gauassian). In addition, it is found that accounting for soil spatial variability in design of retaining walls leads to more economic designs, as it produces smaller probabilities of failure. In other word, negligence of the spatial variability in the design of retaining wall is conservative.
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Papers by Waleed Mahfouz M. A. Youssef
This thesis presents a comprehensive analysis of activities duration of construction projects in the Middle East countries. The analysis was carried out on twenty construction projects including more than 125,000 activities with a total budget of about fifteen billions Egyptian Pounds (EGP) and comprising all engineering, procurement and construction (EPC) activities. The thesis seeks to bridge the gap between theory and application and to utilize a probabilistic scheduling approach that yields reliable estimations of activity duration. The focus is to evaluate the actual behaviour of activities exposed to different types of risk and uncertainty and to derive regression models predicting activities’ durations categorized according to country, type of work, and to the Construction Specifications Institute (CSI) divisions.
First, previous research on the causes of delay and the probabilistic analysis of activities in developing and developed countries has been compiled and critically reviewed. This review indicated that there is no generally accepted Probability Density Function (PDF) to represent the activity duration through the simulation process. However, Beta and Triangular distributions were the mostly used PDF’s.
Then, activity and project durations of different projects such as hospitals, hotels, stadiums, highways, malls, and high rise buildings in Egypt, Kuwait, Saudi Arabia, UAE, Qatar and Oman were analysed. The analysis considered the estimated durations, the actual durations, and the budgets of the EPC activities. It also included the quantitative analysis of causes of delay on the performance of seven repetitive construction activities in a housing project that is composed of 1271 similar houses in Kuwait. Besides, statistical analysis and curve fitting of the estimated versus the actual durations of activities were conducted. In addition, the study developed predictive regression models to estimate the statistics of activities durations. Finally, a special program that uses the concluded PDF and regression models to predict the project’s overall durations at different levels of confidence was developed.
It is found that the three most influencing risks on the time performance of construction activities in Kuwait are: (1) inadequate planning and time scheduling; (2) slow financial and payment procedures; and (3) fluctuation of productivity levels. In addition, it is found that the best PDF to represent activities in construction projects is the lognormal distribution, while the second best PDF is the gamma distribution. Besides, it is shown that the normal distribution has the lowest level of confidence. Furthermore, it is found that as the estimated duration decreases, the relative duration slippage increases. The ratio of the highest, actual activity duration to the corresponding mean duration is always more than 4 for projects in the Middle East, which differs from that suggested in previous studies (1.25). As a general rule, the forecasted project’s overall duration- based on the proposed regression models and utilizing lognormal distribution- tends to be greater than that calculated using conventionally estimated activities. Nevertheless, validation tests showed that the forecasted projects’ durations are good estimates of the real ones. Consequently, these forecasted projects’ durations could oblige contractors to implement different methodologies and alternative plans to reduce the project’s duration.
Thesis Chapters by Waleed Mahfouz M. A. Youssef
This study investigates the effect of spatial variability of soil properties (mass density γs, coefficient of friction tanδ, angle of internal friction (φ), and wall mass density γc, on the factors of safety against sliding (Fs), and overturning (Fo), as well as the maximum bending moment (M) of cantilever retaining walls.
For risk assessment, soil properties are described using appropriate probabilistic models. Deterministic analysis combined with Monte Carlo Simulation (MCS) is employed to analyze both spatially fully correlated and spatially uncorrelated soil profiles.
A FORTRAN program is developed to: (1) generate random variables with both Gauassian and non-Gauassian probability density functions (PDF); (2) simulate possible probability distributions for distinct soil properties; (3) perform repetitive analysis for each set of variable PDFs to generate the population of Fs, Fo, and M; and (4) calculate the statistical parameters of Fs, Fo, and M. The program is then applied to conduct an extensive parametric study.
This parametric study is performed to quantify and assess the effects of model uncertainty and the effect of spatial heterogeneity of soil properties, utilizing two different soil profiles: (1) spatially fully correlated soil profile; and (2) spatially uncorrelated soil profile.
The numerical results show that the effects of spatial variability and uncertainty of input variables on wall safety vary from one variable to the other. Consequently, considerable care should be directed to those variables that have the greatest effects. For typical degrees of uncertainty, it is found that the structural risk is highest when the PDF of tanδ and φ is normal (Gauassian), or has an upper triangular shape (non-Gauassian). In addition, it is found that accounting for soil spatial variability in design of retaining walls leads to more economic designs, as it produces smaller probabilities of failure. In other word, negligence of the spatial variability in the design of retaining wall is conservative.
This thesis presents a comprehensive analysis of activities duration of construction projects in the Middle East countries. The analysis was carried out on twenty construction projects including more than 125,000 activities with a total budget of about fifteen billions Egyptian Pounds (EGP) and comprising all engineering, procurement and construction (EPC) activities. The thesis seeks to bridge the gap between theory and application and to utilize a probabilistic scheduling approach that yields reliable estimations of activity duration. The focus is to evaluate the actual behaviour of activities exposed to different types of risk and uncertainty and to derive regression models predicting activities’ durations categorized according to country, type of work, and to the Construction Specifications Institute (CSI) divisions.
First, previous research on the causes of delay and the probabilistic analysis of activities in developing and developed countries has been compiled and critically reviewed. This review indicated that there is no generally accepted Probability Density Function (PDF) to represent the activity duration through the simulation process. However, Beta and Triangular distributions were the mostly used PDF’s.
Then, activity and project durations of different projects such as hospitals, hotels, stadiums, highways, malls, and high rise buildings in Egypt, Kuwait, Saudi Arabia, UAE, Qatar and Oman were analysed. The analysis considered the estimated durations, the actual durations, and the budgets of the EPC activities. It also included the quantitative analysis of causes of delay on the performance of seven repetitive construction activities in a housing project that is composed of 1271 similar houses in Kuwait. Besides, statistical analysis and curve fitting of the estimated versus the actual durations of activities were conducted. In addition, the study developed predictive regression models to estimate the statistics of activities durations. Finally, a special program that uses the concluded PDF and regression models to predict the project’s overall durations at different levels of confidence was developed.
It is found that the three most influencing risks on the time performance of construction activities in Kuwait are: (1) inadequate planning and time scheduling; (2) slow financial and payment procedures; and (3) fluctuation of productivity levels. In addition, it is found that the best PDF to represent activities in construction projects is the lognormal distribution, while the second best PDF is the gamma distribution. Besides, it is shown that the normal distribution has the lowest level of confidence. Furthermore, it is found that as the estimated duration decreases, the relative duration slippage increases. The ratio of the highest, actual activity duration to the corresponding mean duration is always more than 4 for projects in the Middle East, which differs from that suggested in previous studies (1.25). As a general rule, the forecasted project’s overall duration- based on the proposed regression models and utilizing lognormal distribution- tends to be greater than that calculated using conventionally estimated activities. Nevertheless, validation tests showed that the forecasted projects’ durations are good estimates of the real ones. Consequently, these forecasted projects’ durations could oblige contractors to implement different methodologies and alternative plans to reduce the project’s duration.
This study investigates the effect of spatial variability of soil properties (mass density γs, coefficient of friction tanδ, angle of internal friction (φ), and wall mass density γc, on the factors of safety against sliding (Fs), and overturning (Fo), as well as the maximum bending moment (M) of cantilever retaining walls.
For risk assessment, soil properties are described using appropriate probabilistic models. Deterministic analysis combined with Monte Carlo Simulation (MCS) is employed to analyze both spatially fully correlated and spatially uncorrelated soil profiles.
A FORTRAN program is developed to: (1) generate random variables with both Gauassian and non-Gauassian probability density functions (PDF); (2) simulate possible probability distributions for distinct soil properties; (3) perform repetitive analysis for each set of variable PDFs to generate the population of Fs, Fo, and M; and (4) calculate the statistical parameters of Fs, Fo, and M. The program is then applied to conduct an extensive parametric study.
This parametric study is performed to quantify and assess the effects of model uncertainty and the effect of spatial heterogeneity of soil properties, utilizing two different soil profiles: (1) spatially fully correlated soil profile; and (2) spatially uncorrelated soil profile.
The numerical results show that the effects of spatial variability and uncertainty of input variables on wall safety vary from one variable to the other. Consequently, considerable care should be directed to those variables that have the greatest effects. For typical degrees of uncertainty, it is found that the structural risk is highest when the PDF of tanδ and φ is normal (Gauassian), or has an upper triangular shape (non-Gauassian). In addition, it is found that accounting for soil spatial variability in design of retaining walls leads to more economic designs, as it produces smaller probabilities of failure. In other word, negligence of the spatial variability in the design of retaining wall is conservative.