كليدواژه :
الگوريتم‌هاي فرا ابتكاري , تابع هزينه , حاشيه اطمينان , سازه هيدروليكي
چكيده فارسي :
استفادۀ بهينه از منابع آب يكي از كهن‌ترين هدفهاي بشر است. امروزه با توجه به هدفها و كاربردهاي چندگانۀ سدها، به‌كارگيري تمهيدات مناسب براي بهره‌برداري از سرريزها و مخازن سدها اهميت بالايي دارد. هدف اين تحقيق دستيابي به طول و ارتفاع بهينه براي سرريز اوجي است. به‌منظور تعيين تابع هدف، تغييرات طول سرريز در محدوده 10 تا 30 متر و دورۀ بازگشت سيلاب طراحي در محدودۀ 1000 تا 10000 سال در نظر گرفته شد. با ابزار الگوريتم ژنتيك، بهينه‌سازي در محيط نرم‌افزار MATLAB انجام شد. در اين تحقيق، تأثير طول و ارتفاع سرريز بر هزينۀ ساخت سرريز بررسي و با استفاده از مدل رگرسيون، رابطه هاي تحليلي براي آن ارائه شد. نتايج تحقيق نشان مي دهد طول بهينه براي سرريز 4/14 متر و ارتفاع بهينه 47/31 متر است. به‌طوركلي طراح براي طول و ارتفاع سرريز اوجي سد بالارود، به ترتيب 28 و 34 درصد را به‌عنوان حاشيۀ اطمينان در نظر گرفته است. انتخاب اين مقادير، هزينۀ پروژه را به‌طور چشمگير افزايش مي‌دهد؛ كه نيازمند بازنگري مهندسان در انتخاب حاشيۀ اطمينان مناسب براي ابعاد سرريز با در نظر گرفتن جميع مؤلفه‌هاست.
چكيده لاتين :
Introduction
The cost of dam construction is very high. A lot of dams are broken due to the water passing
through dam crest. The most important factor which causes this is, insufficient spillway
capacity. The aim of present study was investigating optimal height and length for OgeeCrested spillway because such height and length minimizes the cost of spillway
construction. In order to determine objective function, the spillway length variations were
considered in the range of 10 to 30 m and the flood return period was estimated in the range
of 1000 to 10,000 years. Optimization was done with using genetic algorithm in MATLAB
software environment. In fact, the aim of this study was investigating the effect of height
and length of spillway on the cost of spillway construction, therefore, Analytical
relationships presented with using regression model. The main function of Ogee-Crested
spillway is providing ideal conditions for passing designed flood from upstream to
downstream. Bagatur & Onen in 2016, used gene expression planning (GEP) models as an
alternative approach to predicting appearance features and spillway design coefficients and
therefore, proposed new relationship, for Ogee-Crested spillway. It was found that GEP is
much better than regression model for predicting Ogee-Crested spillway characteristics.
Haghbin in 2015 proposed that using multi-objective genetic algorithm can optimize
spillway geometrical dimensions. The results of this study provide the appropriate height
and length for the spillway.
Methodology
The question of this research is, what is the appropriate height and length for the OgeeCrested spillway of Ballarood Dam? In this study, the Ballarood Reservoir Dam was
selected as a case study and genetic algorithm process was used for optimizing this issue.
First, objective function was coded and then, this function was added to the MATLAB
software. In order to provide Spillway cost function, spillway length variations were
considered within the range of 10 to 30 m. In modeling with using genetic algorithm
method, first, the length component was divided into discrete data which included integer
numbers from 10 to 30. Keeping in view each optimization problem has its decision variables, constraints, and
objective function. The decision variables of this present study, namely the Ballarood Dam
spillway decision variables, included height (P), length (L), and flood return period (T). The
models derived from algorithm modeled with using regression, and their meaningful level
was obtained.
Results and Discussion
In this study, after determining objective function and choosing suitable operators,
optimization was done with using genetic algorithm; the most appropriate response was
reported as problem answer.
Considering the maximum design load (Hd = 50.50 m) and (T = 10000 years), the optimum
dimensions and costs were obtained by function: The optimal spillway length and height
was was found to be 14.4 m and 47.31 m respectively.
It needs to be mentioned that the designed Ballarood Dam spillway is 20 meters in length.
With optimization by genetic algorithm, this length was reduced to 14.4 meters. Comparison
of the results showed that if this amount of spillway had been applied during construction of
the dam, it could have saved up to 28% on project implementation economically. The output
value for the spillway height in this study was 31.47 m and the operational value for the
height was 47.7 m. Comparison of these two data indicates 34% higher altitude allocation
for the margin of confidence.
Conclusions
One of the goals of this study was reducing costs. Keeping this in mind, the operational cost
for the spillway length and height respectively were 31% and 28% more than designed
values, with reduction of spillway length and height, operational costs was greatly reduced.
The other goal of this study was optimizing dimensions of spillway but according to the
principles of genetic algorithm, we could not achieve to 100% of this goal. In the other
words, the genetic algorithm determines the optimal dimensions but it does not determine
the best answer. According to this fact, we can find other optimal dimensions for this
problem, which is possible by adding more constraints to the problem. The genetic
algorithm has some weaknesses, which include: Extremely high sensitivity to the population
size and mutation operators which imposes high costs on the whole project in high
reliability dam construction projects. Therefore, we recommend in future dam construction
studies the scholars take into consideration the issue of benefits and costs future projects
along with consideration of and also the high factor of safety in dam construction projects.
