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15-04-2015, 03:41 PM
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رسالة دكتوراه في إدارة المشروعات - PROBABILISTIC MODELS FOR CONSTRUCTION PROJECTS' DURATIO


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.





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15-04-2015, 08:01 PM
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    #2  
شكرا لك اخي على الكتاب وتم رفعه الى سرفر البوابة


16-04-2015, 03:50 PM
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    #3  
The Published Paper is
Construction Activities Duration Patterns in the Middle East

22-04-2015, 01:48 PM
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رقم العضوية: 296062
تاريخ التسجيل: Jul 2009
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    #4  
رسالة الدكتوراه والورقة البحثية تدرس مخاطر التشييد بالشرق الأوسط وكيفية التغلب عليها وعلى تأخيرات مشروعات التشييد كما تم دراسة كيفية التبؤ بمدة المشروع في ظل الدرجات المختلفة من المخاطر وعدم التأكد المؤثرة عليه، يشرفني مشاركتكم إياها ومشاركة أي طالب عالم
يمكنكم مشاركتها كيفما شئتم..
د. وليد محفوظ ...


Construction Activities Duration Patterns in the Middle East



http://www.sapub.org/global/showpape...em.20130204.04


PROBABILISTIC MODELS FOR CONSTRUCTION PROJECTS' DURATIONS IN THE MIDDLE EAST




http://www.mediafire.com/view/17657p...DDLE_EAST.pdf9

 


رسالة دكتوراه في إدارة المشروعات - PROBABILISTIC MODELS FOR CONSTRUCTION PROJECTS' DURATIO

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