Gebrail Bekdaş

Prof. Dr. Gebrail Bekdaş

İstanbul University-Cerrahpaşa
orcid

Research Focus & Metrics

Academic Career Length

16Years (2011-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 September 2011 in Engineering Structures
Verified
Journal Article
Closed access
Gebrail BekdaşGebrail Bekdaş
Gebrail Bekdaş
Sinan Melih NigdeliSinan Melih Nigdeli
Sinan Melih Nigdeli

1 June 2013 in International Journal of Mechanical Sciences
Verified
Journal Article
Closed access
Gebrail BekdaşGebrail Bekdaş
Gebrail Bekdaş
Sinan Melih NigdeliSinan Melih Nigdeli
Sinan Melih Nigdeli

25 June 2023 in Materials
Verified
Journal Article
Open access
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CCCelal Cakiroglu
Celal Cakiroglu
Yaren AydınYaren Aydın
Yaren Aydın
Gebrail BekdaşGebrail Bekdaş
Gebrail Bekdaş
Zong Woo GeemZong Woo Geem
Zong Woo Geem
Basalt fibers are a type of reinforcing fiber that can be added to concrete to improve its strength, durability, resistance to cracking, and overall performance. The addition of basalt fibers with high tensile strength has a particularly favorable impact on the splitting tensile strength of concrete. The current study presents a data set of experimental results of splitting tests curated from the literature. Some of the best-performing ensemble learning techniques such as Extreme Gradient Boosting (XGBoost), Light Gradient Boosting Machine (LightGBM), Random Forest, and Categorical Boosting (CatBoost) have been applied to the prediction of the splitting tensile strength of concrete reinforced with basalt fibers. State-of-the-art performance metrics such as the root mean squared error, mean absolute error and the coefficient of determination have been used for measuring the accuracy of the prediction. The impact of each input feature on the model prediction has been visualized using the Shapley Additive Explanations (SHAP) algorithm and individual conditional expectation (ICE) plots. A coefficient of determination greater than 0.9 could be achieved by the XGBoost algorithm in the prediction of the splitting tensile strength.

28 January 2023 in Sustainability
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Journal Article
Open access
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Yaren AydınYaren Aydın
Yaren Aydın
Umit IsikdagUmit Isikdag
Umit Isikdag
Gebrail BekdaşGebrail Bekdaş
Gebrail Bekdaş
Sinan Melih NigdeliSinan Melih Nigdeli
Sinan Melih Nigdeli
Zong Woo GeemZong Woo Geem
Zong Woo Geem
In the design of reliable structures, the soil classification process is the first step, which involves costly and time-consuming work including laboratory tests. Machine learning (ML), which has wide use in many scientific fields, can be utilized for facilitating soil classification. This study aims to provide a concrete example of the use of ML for soil classification. The dataset of the study comprises 805 soil samples based on the soil drillings of the new Gayrettepe–Istanbul Airport metro line construction. The dataset has both missing data and class imbalance. In the data preprocessing stage, first, data imputation techniques were applied to deal with the missing data. Two different imputation techniques were tested, and finally, the data were imputed with the KNN imputer. Later, a balance was achieved with the synthetic minority oversampling technique (SMOTE). After the preprocessing, a series of ML algorithms were tested with 10-fold cross-validation. Unlike the studies conducted in previous research, new gradient-boosting methods such as XGBoost, LightGBM, and CatBoost were tested, high classification accuracy rates of up to +90% were observed, and a significant improvement in the accuracy of prediction (when compared with previous research) was achieved.

1 March 2017 in KSCE Journal of Civil Engineering
Verified
Journal Article
Open access
PDF file
Sinan Melih NigdeliSinan Melih Nigdeli
Sinan Melih Nigdeli
Gebrail BekdaşGebrail Bekdaş
Gebrail Bekdaş
The design of tuned mass dampers for reduction of seismic vibrations in multiple degree of freedom structures is also a complex problem and the optimization of design parameters of tuned mass damper are needed for the best reduction of structural responses. In the optimization process, frequency or time domain solutions can be iteratively used. In this paper, a frequency based optimization technique is presented to find design variables such as mass, period and damping ratio of tuned mass damper on the top of a structure. A music inspired metaheuristic algorithm called harmony search is employed to reach the optimum solution. The optimum results were obtained for two 10-story and one 40-story structures. According to comparisons with time domain based method, frequency domain based methods is effective to reduce maximum values and to obtain a steady stead response for critical excitations.

24 April 2020 in Applied Sciences
Verified
Journal Article
Open access
PDF file
AKAylin Ece Kayabekir
Aylin Ece Kayabekir
Gebrail BekdaşGebrail Bekdaş
Gebrail Bekdaş
Sinan Melih NigdeliSinan Melih Nigdeli
Sinan Melih Nigdeli
Zong Woo GeemZong Woo Geem
Zong Woo Geem
In this study, the music-inspired Harmony Search (HS) algorithm is modified for the optimization of active tuned mass dampers (ATMDs). The modification of HS includes the consideration of the best solution with a defined probability and updating of algorithm parameters such as harmony memory, considering rate and pitch adjusting rate. The design variables include all the mechanical properties of ATMD, such as the mass, stiffness and damping coefficient, and the active controller parameters of the proposed proportional–integral–derivative (PID) type controllers. In the optimization process, the analysis of an ATMD implemented structure is done using the generated Matlab Simulink block diagram. The PID controllers were optimized for velocity feedback control, and the objective of the optimization is the minimization of the top story displacement by using the limitation of the stroke capacity of ATMD. The optimum results are presented for different cases of the stroke capacity limit of ATMD. According to the results, the method is effective in reducing the maximum displacement of the structure by 53.71%, while a passive TMD can only reduce it by 31.22%.