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Öğe Advanced tree-based machine learning methods for predicting the seismic response of regular and irregular RC frames(Elsevier Science Inc, 2024) Demir, Ahmet; Sahin, Emrehan Kutlug; Demir, SelcukIn this study, predicting the maximum drift ratio (MDR) for two types of structures: 8-story regular (R8) and vertically irregular (IR8) reinforced concrete (RC) frames are focused. To accomplish this, advanced tree-based machine learning (ML) methods, namely Random Forest (RF), eXtreme Gradient Boosting (XGBoost), and Stochastic Gradient Boosting (SGB) are utilized. 2300 ground motion (GM) records, includes twenty-one input parameters and their nonlinear time history analyses results are considered as a dataset. The performance of the RF, XGBoost, and SGB models was examined considering the impact of the data pre-processing issue to test whether the use of data pre-processing approaches in model development could improve the prediction performance of the advanced ML models. Various data pre-processing techniques, including outlier detection using boxplot, missing data imputation using RF, data transformation using log transformation, and feature selection using Hill Climbing are employed as part of ML pipeline. The models' performance is evaluated using six different well-established statistical evaluation metrics. Subsequently, the results are systematically compared to identify the most effective prediction model. Our findings highlight the substantial impact of data pre-processing on the performance of ML models when predicting seismic responses, specifically the MDR of RC frames. Notably, RF consistently outperformed other ML models for both R8 and IR8 structures in the case of the simple ML pipeline strategy and data pre-processing approach. The RF model achieved R2 scores of R2 = 0.87 and R2 = 0.91 on the test data before implementing data pre-processing for R8 and IR8, respectively. After data preprocessing, R2 scores showed an improvement of 12% and 6.22% in the cases of R8 and IR8. In contrast, the performance scores of SGB consistently fell behind those of RF and XGBoost models.Öğe Assessment of Damages in Precast Industrial Buildings in the Aftermath of Pazarcık and Elbistan Earthquakes(Taylor & Francis Ltd, 2024) Senel, Sevket Murat; Kayhan, Ali Haydar; Palanci, Mehmet; Demir, AhmetTwo major earthquakes with moment magnitudes of 7.7 and 7.6 struck the districts of Pazarc & imath;k and Elbistan, causing thousands of deaths and severe damage. A lot of buildings located in 11 different cities were damaged or collapsed. In addition to urban areas, industrial regions were also affected and damaged by these earthquakes. In this study, the results of assessment studies performed in the industrial zones located in Malatya, Ad & imath;yaman, Kahramanmaras, Osmaniye, and Hatay cities are presented. The maximum seismic demands instrumented by the strong ground motion stations were first investigated. Then, the acceleration records obtained from the stations near the visited industrial zones were studied, and the spectral demands were compared to the code spectra. Obtained results have revealed that spectral acceleration and displacement demands are higher than that of design earthquake in many stations. Even in some stations, it was determined that the spectral demands, especially in the constant velocity region where the periods of precast industrial buildings are located, also exceeded the demand of the maximum earthquake of the code. After demand assessment studies, the structural properties of existing precast buildings are presented, and the reasons behind the damages are discussed. Site inspections have shown that connection failures are the most common type of damage observed. The overturning of roof girders and shear damage at corbels and beam ends are the typical forms of joint failures. Column flexural failures and other factors that cause the structural damage are discussed and explained. Non-structural damage was also determined in many buildings. Damage to suspended ceilings, facade cladding, products and equipment, and partition walls are the typical examples of non-structural damage observed. Reconnaissance studies have shown that the damaged building ratio in Kahramanmaras Turkoglu and Ad & imath;yaman Petrol industrial zones is significantly higher than in other regions visited. Damage distributions in Kahramanmaras Turkoglu and Ad & imath;yaman Petrol industrial zones, where comprehensive information was gathered, are presented and evaluated.Öğe Evaluation the effect of amplitude scaling of real ground motions on seismic demands accounting different structural characteristics and soil classes(Springer, 2024) Demir, Ahmet; Palancı, Mehmet; Kayhan, Ali HaydarSelection and scaling of input ground motion records for nonlinear dynamic analysis of structures has become an important issue and studies on this subject can provide valuable information for earthquake engineering practice. In this study, the effect of different amplitude scaling approaches and scaling levels based on spectrum-compatible selection were investigated for various local soil classes. A recent Turkish Building Earthquake Code was considered and simple structural models that reflected the different characteristics of structures were employed. The dynamic attributes of the models were represented by using different lateral strength ratios, post yield stiffness ratios and natural vibration periods. The maximum displacement, residual displacement, and input energy demands were used to evaluate the efficiency of scaling approaches and levels. In addition, some of the commonly used intensity measures that reflected the different characteristics of ground motions were considered for the evaluation. Significance of the uncertainties associated with structural models and their impact on the results were also statistically evaluated by variance analysis. Moreover, a probability-based method was adapted and influence of scaling approaches and their dependence to local soil types was established by examining the statistical mean of maximum displacement demands in terms of amplification factors. Results demonstrated that distribution of mean of the structural responses and the intensity measures are free from scaling approaches and scaling levels, and the differences between the demands obtained for different scaling levels are statistically insignificant for 90% confidence level. Probability-based evaluations have also revealed that amplification factors for seismic demands can be assumed as independent from scaling approaches, scaling levels and local soil classes.Öğe The investigation of displacement demands of single degree of freedom models using real earthquake records compatible with TBEC-2018(PAMUKKALE UNIV, 2021) Palancı, Mehmet; Kayhan, Ali Haydar; Demir, AhmetAdvances in earthquake engineering play a role in the development of seismic codes all over the world. The new version of Turkish Building Earthquake Code (TBEC) has also been published in 2018. Thanks to the technological developments, real acceleration records to be used in dynamic analysis of structures have been easily accessible. In this study, the variation of maximum displacement demands of single degree of freedom (SDOF) systems determined via dynamic analysis by using real earthquake records compatible with TBEC are investigated. For this purpose, 120 SDOF systems which represent behavior of variety of structural topologies were created by combination of different lateral strength capacity ratios, structural periods, hysteretic models and post-yield stiffness ratios. In order to obtain ground motion records, two different level of seismic intensity level and three different local soil classes are considered. 30 real ground motion record sets for each seismic intensity level and local soil class are used for detailed assessment of tendency and variation of maximum displacement demands. Results indicated that (a) effect of different hysteretic models on displacement demands is negligible, (b) the mean displacement demands are more conservative than median displacement demands for the sets, (c) displacement demand variation of the sets are high and not evenly distributed, (d) the variation of the demands changes randomly depending on local soil class and earthquake level, (e) lateral strength ratio and post-yield stiffness are efficient on the variation of the demands.Öğe Investigation of the effect of real ground motion record number on seismic response of regular and vertically irregular RC frames(Elsevier Science Inc, 2022) Demir, AhmetNonlinear time history analysis is an analytical method generally used in performance-based seismic design. With this method, seismic responses are obtained more realistically. Selection of ground motion records for nonlinear time history analysis is an important step since it strongly affects the analysis results. Therefore, it has always been a matter of curiosity to investigate the effect of the characteristics, content and number of the records on the analysis results. In this study, seismic responses of regular and irregular RC frames were investigated by varying the number of real ground motion records in a set. For this purpose, 13 different groups that contain three to hundred real ground motion records in size in a set have been considered and ten different earthquake record sets are obtained for each group. Ground motion selection procedure of Eurocode-8 was considered and a total of 130 sets were used for nonlinear response analysis of RC frames. Global drift ratio, maximum floor acceleration, inter-story drift ratio and six different intensity measures (IMs) were used to investigate the effect of the number of records. According to analysis results, nonlinear responses of RC frames are more stable and might be sufficient when the number of real records in a set is higher than seven according to Eurocode-8. Results indicate that if the number of real records in a set are lower than seven, conservative seismic responses can be found since the maximum rather than mean response values are used. It is observed that dispersion of seismic demands and mean to median ratios can be increased if the number of real records in a set is higher than ten. In addition, the correlation between some of IMs and seismic demands increase when the number of records in a set increased from three to seven and it remains stable from seven to hundred records. Furthermore, 7, 8, 15 and 22 records show the lowest error terms of considered engineering demand parameters for regular and irregular RC frames.Öğe Maksimum ve kalıcı yer değiştirme talepleri açısından TBDY 2018 ve DBYBHY 2007 deprem yönetmeliklerinin karşılaştırılması(Pamukkale University, 2023) Demir, AhmetSeismic codes are updated by taking into account the information obtained as a result of scientific studies and the observations after earthquakes about the behavior of the building. In Turkey, the Turkish Building Earthquake Codes (TBEC) has also been published in 2019, instead of the Turkish Earthquake Codes (TEC). Both seismic codes contain definitions for nonlinear dynamic analysis for the design and/or evaluation of structures. However, in TBEC, both the definition of the design spectrum and the spectral parameters used to obtain the design spectrum for any location in Turkey have changed. In order to evaluate the effects of these changes on the drift demands, nonlinear dynamic analyzes of single degree of freedom (SDOF) systems with different periods and lateral strength ratios were made according to both TBEC and TEC. Then, mean of the maximum and residual drift demands and the scattering of these demands were compared. For this purpose, totally 72 different TSD systems were considered. For the analysis of these systems, 84 and 168 ground motion record sets were used according to TEC and TBEC (different earthquake zones, soil classes and cities), respectively. When the results are examined; it is seen that a) the design spectrums change according to the soil classes and cities, b) the maximum and residual drift demands change depending on the earthquake levels and soil classes, c) in some cities, the demands obtained with TBEC, and in some cities, the demands obtained with TBEC are higher, d) drift demands scattering within the set is high.Öğe Multi-functional solution model for spectrum compatible ground motion record selection using stochastic harmony search algorithm(Springer, 2022) Kayhan, Ali Haydar; Demir, Ahmet; Palancı, MehmetSelection of appropriate ground motion (GM) records for nonlinear dynamic analysis (NDA) of structures plays a crucial role to estimate structural responses reasonably. In this study, a multi-functional solution model utilizing stochastic harmony search (HS) algorithm is proposed to obtain scaled or unscaled real GM component sets for uni-directional analysis of two-dimensional structural models and GM component pair sets for bi-directional analysis of three-dimensional structural models. The solution model allows to consider compatibility between target spectrum and both mean spectrum and individual spectra besides desired spectral variability. Uniform hazard spectrum, conditional mean spectrum or scenario-based spectrum can be selected as target spectrum. Combined response spectra of selected component pairs such as SRSS, geometric mean and maximum directional can also be handled by the solution model. To demonstrate the efficiency of the solution model, various examples were presented. In addition, a sensitivity analysis was performed to evaluate the effect of HS parameters on the solution accuracy. Results show that the proposed solution model can be regarded as efficient to obtain appropriate GM record sets to be used for NDAs within a probabilistic seismic design and/or performance assessment framework.Öğe Probabilistic assessment for spectrally matched real ground motion records on distinct soil profiles by simulation of SDOF systems(Techno-Press, 2021) Demir, Ahmet; Palancı, Mehmet; Kayhan, Ali HaydarSelection of appropriate ground motion records for dynamic analysis has uttermost importance since it significantly affects structural responses which are used for seismic performance assessment of buildings. This study focuses on probabilistic assessment of several record selection strategies that apply different level of constraints for spectrally matched real ground motion records. For this purpose, single degree of freedom (SDOF) systems with various lateral strength capacity ratios, vibration periods and hysteretic models were considered to cover broad type of structural systems and maximum displacement demands of SDOF systems were obtained by nonlinear dynamic analyses. Using the analysis results, central tendency of maximum displacement demands was evaluated. Confidence intervals of the demands were also estimated in probabilistic manner. In addition, non-exceedance probability curves of the displacement demands were constructed. Results indicate that using supplementary constraints about spectral matching, it is possible to control the variation of spectral accelerations and hence the variation of seismic displacement demands. In conclusion, displacement demands can be obtained for code-or probability-based design/performance assessment with appropriate selection approach considering desired variation which can be determined from either probabilistic or deterministic seismic hazard analysis.Öğe Quantifying the effect of amplitude scaling of real ground motions based on structural responses of vertically irregular and regular RC frames(Elsevier Science Inc, 2023) Palanci, Mehmet; Demir, Ahmet; Kayhan, Ali HaydarIncreasing number of real ground motion (GM) record databases raised nonlinear dynamic analysis (NDA) as an attractive option to determine structural response statistics. Structural responses are sensitive to input motions and the appropriate selection and scaling of real GMs is one of the crucial topics in earthquake engineering. In this paper, the influence of amplitude scaling on important earthquake demand parameters (EDPs), namely, global drift ratio, inter-story drift ratio and maximum floor acceleration, were studied using different scaling approaches and scaling limits. Eurocode-8 was used as a reference seismic code and amplitude scaling effects on structural responses of vertically irregular and regular structures were quantified. Efficiency and sufficiency of amplitude scaling were assessed in terms of mean, dispersion and non-exceedance probability curves of the EDPs. Statistical distribution of GM characteristics and their dependence on GM amplitude scaling were also discussed. Evaluations have shown that similar mean responses can be obtained regardless of scaling limits, approaches, and building topology if spectral shape compatibility is ensured. Furthermore, results demonstrated that neither building regularity nor scaling of GMs influenced the statistical distribution of ground motion parameters and non-exceedance probability curves of the EDPs. In fact, it was revealed that record selection scenario including spectral compatibility of individual GMs had a dramatic impact on dispersion and exceedance probability of structural responses.Öğe Response- and probability-based evaluation of spectrally matched ground motion selection strategies for bi-directional dynamic analysis of low- to mid-rise RC buildings(Elsevier Science Inc, 2023) Demir, Ahmet; Kayhan, Ali Haydar; Palanci, MehmetIn this study, the effect of different strategies which consider various levels of constraints for spectrally matched ground motion (GM) selection on seismic responses of the buildings was evaluated. For this, six different threedimensional buildings and three different local soil classes were considered. Various GM record sets were used for each strategy and local soil class pair to perform bi-directional nonlinear dynamic analyses of the buildings and maximum global and maximum inter-story drift ratio demands were obtained. To evaluate the efficiency of proposed strategies, the mean and dispersion of the demands were investigated. Then, the differences among the means of the seismic demands obtained for the strategies were evaluated using the analysis of variance method. Moreover, probability curves of the demands were constructed and compared. The results indicate that i) the mean of the demands generally used for code-based performance assessment can be estimated more consistently by the proposed strategies; ii) the supplemental constraints about spectral matching allow to control the dispersion of the spectral acceleration values of selected GMs and hence the dispersion of the demands; iii) using the appropriate one of the proposed strategies, GMs with desired dispersion of spectral accelerations can be acquired for probability-based performance assessment.
