MCBÜ Açıkerişim Sistemi :: Browsing by Author "Gücüyen, E"

Browsing by Author "Gücüyen, E"

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Estimation of compression strength of polypropylene fibre reinforced concrete using artificial neural networks
Erdem, RT; Kantar, E; Gücüyen, E; Anil, Ö
In this study, Artificial Neural Networks (ANN) analysis is used to predict the compression strength of polypropylene fibre mixed concrete. Polypropylene fibre admixture increases the compression strength of concrete to a certain extent according to mix proportion. This proportion and homogenous distribution are important parameters on compression strength. Determination of compression strength of fibre mixed concrete is significant due to the veridicality of capacity calculations. Plenty of experiments shall be completed to state the compression strength of concrete which have different fibre admixture. In each case, it is known that performing the laboratory experiments is costly and time-consuming. Therefore, ANN analysis is used to predict the 7 and 28 days of compression strength values. For this purpose, 156 test specimens are produced that have 26 different types of fibre admixture. While the results of 120 specimens are used for training process, 36 of them are separated for test process in ANN analysis to determine the validity of experimental results. Finally, it is seen that ANN analysis predicts the compression strength of concrete successfully.
Experimental Study on Pipe Sections against Impact Loading
Gücüyen, E; Erdem, RT; Kantar, E
Pipelines are significant structural systems that transfer necessary materials from one place to another. They are under the effect of static and dynamic loads during their service lives. Investigations have become important to determine the effects of sudden dynamic loads with technological developments. Researchers study the mechanical properties of different materials and structural members under dynamic effects such as earthquake, wind, blast, rock falling and vehicle crushing. For this purpose, different test setups have been developed to investigate the behaviour of test members. In this study, galvanized and water filled galvanized pipe sections having three different diameter values are produced in a laboratory to perform tests under impact loading. The behaviour of the pipes is determined by free falling test apparatus. In addition, measurement devices as accelerometer, dynamic force sensor, lvdt, and data logger are used in the experimental program. So, acceleration, impact force, and displacement values are obtained during the tests. Besides, damage developments of the pipes are also observed to determine the impact resistances of test members. The results are compared to each other and it is stated that while acceleration and impact force values decrease, displacement values increase as the test members approach to collapse damage situation.
Non-linear analysis of reinforced concrete slabs under impact effect
Erdem, RT; Gücüyen, E
Most of the existing structures are designed to resist static loads only. Various researchers indicate that sudden loads affecting structural members should also be considered in the design phase. Surfaces of many structures are covered with concrete slab members that are under the effect of sudden loads such as accidental drops, rock falls, or military attacks. A non-linear analysis of RC slabs is performed in this study using the Abaqus software. Impact parameters such as accelerations, velocities, displacements, impact forces, and energy capacities, are determined for each slab.
Experimental and Numerical Investigation of Steel Sections under Impact Effect
Gücüyen, E; Kantar, E; Erdem, RT; Alicioglu, MB
Experimental and numerical behaviour of steel test specimens with various types of joints is investigated in this study. A drop weight test setup with necessary test equipment is used for this purpose. The mass and drop height of the hammer is taken to be constant so that the same impact energy can be applied on test specimens. The acceleration, displacement, impact load, drop numbers and drop durations, are obtained through experimental study. In addition, development of damage to test specimens is observed during tests. Numerical analyses of behaviour of test specimens under impact load are also conducted to verify test results using the Abaqus software, and a comparison of results is made.
MACHINE LEARNING BASED PREDICTION OF COMPRESSIVE STRENGTH IN CONCRETE INCORPORATING SYNHTHETIC FIBERS
Erdem, RT; Çiftçioglu, AÖ; Gücüyen, E; Kantar, E
Different types of fibers are added to the concrete mixture to improve its behavior under different loading cases. This study intends to investigate the compressive strength of concrete cubic samples in which synthetic macro fibers are added in different amounts. For this purpose, a total of 72 cubic samples are produced in the experimental program. Axial pressure test is applied to cubic samples and 7 and 28 days compressive strength values are obtained in the end. However, a lot of effort has been spent to complete the time-consuming laboratory tests. To overcome this situation, four machine learning methods-Xgboost, Random Forest, Decision Tree, and Multiple Linear Regression-are adapted for efficient compressive strength forecasting. Moreover, four metrics are employed for a more meaningful evaluation of models: R2, RMSE, MAE, and MAPE. Remarkably, all models achieved R2 values exceeding 90%, with Xgboost notably reaching an impressive R2 value of 97%. This highlights the effectiveness of integrating machine learning in predicting compressive strength, offering a viable alternative to traditional laboratory tests. Incorporating the Shapley Additive exPlanation (SHAP) method, the study provides a detailed analysis of the models' interpretability. SHAP analysis revealed that Day and Fiber have been identified as crucial features influencing compressive strength predictions. Localized SHAP analyses for specific samples further enhanced the understanding of individual predictions, emphasizing the practicality and transparency of machine learning in structural engineering. The promising results of this study indicate the potential for further advancements in enhancing performance, utilizing machine learning insights.
Comparative analysis of tripod offshore structure
Gücüyen, E; Yigit, ME; Erdem, RT; Gökkus, U
Marine structures are nowadays used in a variety of ways. The analysis of a tripod-type offshore structure sixty m in total height is performed in this study. In addition to operation-related loads, the structure is also under the effect of wind and wave loads. While the Eurocode velocity profile is used to calculate wind forces, the Airy wave velocity profile is utilized to determine wave forces. The model is created by a finite elements analysis program, and is composed of fluid and structural parts. The interaction of the parts is ensured by Coupled Eulerian Lagrangian (CEL) technique.
Numerical Analysis of Deteriorated Sub-sea Pipelines under Environmental Loads
Gücüyen, E
The significant point is the bidirectional interaction technique in FSI analysis while investigating subsea corrosion effect. By this way, pipe environment is accurately modelled and fluid effects are also considered. The effect of external corrosion defects on structural behaviour of a pipeline is studied by creating a nonlinear numerical model based on the finite element method according to ABAQUS analysis program. Corrosion losses of sections are obtained from experimental results and applied to the model. Numerical model is formed by a span of sub-sea pipeline that is subjected to environmental loads. Seismic and wind-generated irregular wave loads are considered as environmental loads. Irregular wave is represented with equivalent eight regular waves via FFT. The pipe is modelled according to two different types which are non-corroded(intact) and corroded (deteriorated) to demonstrate corrosion effects on it. The visible type of corrosion in marine environment is named 'pitting' corrosion, in which the material loss is locally interpenetrated over the surface. By considering this situation, the corroded and non-corroded pipes are modelled as 3D solid elements. The main point is revealing how the subsea corrosion affects the structural behaviour of pipelines on the basis of implementation of experimental results to a model structure due to changes of stresses and displacement.
Analysis of submarine outfalls subjected to wave load
Gücüyen, E
Significant improvements have been made in recent years in the field of submarine outfall construction technology. Such an advancement, resulted in structural improvements of submarine outfalls, especially with regard to diffuser pipes, risers, and ports. The paper focuses on the modelling of one part of submarine outfall, namely the diffuser pipes made of various materials, and on the effects of their surroundings (internal and external flows). The fluid structure interaction technique is applied in the analyses. The analyses conducted in the paper show that the highest stress values are obtained in the pipe-riser connections. Highest displacements are observed when wave load is axially applied on the structure.
Irregular Wave Effects on Dynamic Behavior of Piles
Gücüyen, E; Erdem, RT; Gökkus, Ü
The paper presents computer-aided numerical analyses which are utilized to investigate the dynamic behavior of piles under wind-generated irregular wave loads. A pile is modeled as a single-degree-of-freedom system. The equation of motion of the system is numerically integrated using a fourth order Runge-Kutta method. The equation of motion includes shape function that is obtained approximately. It is needed to compare the solutions with another method to determine the approximation leads whether significant differences or not. For this purpose the dynamic behavior of structure is modeled by the Time History Tool of SAP 2000 and the results compared with those found by a single-degree-of-freedom system. Irregular wave is represented with equivalent regular waves with two different approaches; based on either superimposed multi-sinusoidal wave (Loading I) or significant wave (Loading II), utilizing the energy spectrum. Wave forces are obtained from Morrison Equation. The analyses account for a soil-pile interaction in a simplified way. As the lateral ground pressure changes by delving deep into the ground, soil spring stiffness also changes. Those forces are calculated separately for different depths and taken into account in both analyses. Lateral displacement of the employed pile varying with the time is obtained from analyses for Loading I and Loading II. Critical results are obtained from which loading is determined. Finally, the frequencies of the external loads and natural frequency of pile are compared to examine whether the resonance came true or not.
FLUID STRUCTURE INTERACTION ANALYSES OF ELEVATED STORAGE TANK UNDER SEISMIC LOAD
Erdem, RT; Gücüyen, E
Elevated storage tanks are used to store fresh and waste water, cereal, oil and petrochemical materials. Therefore they serve in a wide area of utilization in this day and age. Analysis of a half full with water elevated storage tank is performed in the scope of this study. The structure is composed of a steel circular storage tank and frame typed steel stager. The structure is under the effect of earthquake loads as well as operational ones. Numerical model is generated by Finite Elements Analysis (FEA) software including fluid and structure parts. The interaction of the parts is provided by Coupled Eulerian Lagrangian (CEL) technique. While the structure constitutes the Lagrangian part, the fluid constitutes the Eulerian part. Interaction of Eulerian and Lagrangian parts are provided by general contact algorithms. Free surface movement of the water, maximum displacements and natural frequency values with related mode shapes of the structure are obtained after numerical analysis. Numerical results are verified by semi -analytical model, where the structure is modelled as single degree of freedom system. The accordance between results is numerically and visually obtained. The turbulent movement of water under the influence of an earthquake is modelled by utilizing the CEL technique. So, the effect of the dynamic pressure induced by the turbulence on the tank and the structural system has been taken into consideration.
Experimental study on hollow section joints under impact loading
Erdem, RT; Kantar, E; Gücüyen, E; Alicioglu, MB
Steel sections with four different joint types, subjected to sudden impact, are investigated in this study. A drop weight test setup was developed for this purpose. Impact tests were performed for two different energy levels. Acceleration-time, displacement-time, impact load-time, and impact load-displacement graphs were developed and presented. It was established that the behaviour of test specimens is affected by joint types and impact energy applied. Failure damage situation occurs earlier when rigidity of specimens decreases and when higher level of impact energy is applied.
Analysis of offshore wind turbine tower under environmental loads
Gücüyen, E
Researchers have started to use numerical methods in the fluid-structure interactive solutions with the advancing of computing technology. There are few studies investigating bidirectional fluid structure interaction (FSI) analysis due to requirements of high computer capacity. This insufficiency is attempted to be corrected in this study. Offshore wind turbine tower is selected to employ the method under environmental loads. To detect accuracy of the numerical analysis, the tower is modelled as a single-degree-of-freedom (SDOF) system. The equation of motion of the system is numerically integrated by using a fourth-order Runge-Kutta method. Time-varying lateral displacement of the tower and first natural frequency values are obtained from analysis. Afterwards, the structure and the environment are modelled in ABAQUS finite elements program. Bidirectional FSI technique is applied to the structure due to the interaction between ABAQUS/CFD-ABAQUS/Explicit. The accuracy of SDOF and bidirectional FSI analyses results is determined in the end.
ESTIMATION OF COMPRESSIVE STRENGTH OF CEMENT MORTARS
Erdem, RT; Ozturk, AU; Gücüyen, E
Due to several advantages of cementitious materials especially mortars, they are widely used in construction works. It is important to determine the mechanical properties of cementitious materials to understand their behavior under different effects. In this study, Artificial Neural Networks (ANN) analysis is used to predict the 7 and 28 days compression strength values of cement mortars. Physical-mechanical properties such as flow, setting time and compressive strength of cement mortars incorporating of different chemical admixtures such as air-entraining admixture (HS), naphthalene sulfonate based (SPNS) and modified polymer (SPMP) based admixtures have been determined. The aim of the usage of combinations of air-entraining admixture with two different based superplasticizers is to form different inner structure affecting on compressive strength. All admixtures are used with three different ratios by cement weight and one of them is for overdosage effect. ANN analysis has been performed to predict the compression strength values after 7 and 28 days, in correlation with experimental part of the study. According to this view, 28 sets have been prepared with different combination of admixtures. At early ages, HS015-SPNS2.0 series had the lowest strength whereas the highest compressive strength at 28 days were obtained for HS005-SPMP0.8 series. Obtained compression strength values after 7 and 28 days have also been predicted by ANN analysis. It is stated that the established ANN model indicates a great capacity to predict the compressive strength values in the end.
NUMERICAL MODELLING OF SUDDEN CONTRACTION IN PIPE FLOW
Gücüyen, E; Erdem, RT; Gökkus, Ü
In the present work, full-scale numerical simulations of incompressible fluid flow through different locations of sudden contractions are studied according to Computational Fluid Dynamics (CFD) technique. Finite Elements Method is used to numerically solve governing equations via the commercial program ABAQUS including CFD code. Four different locations of contraction zone are utilized to determine the effect of location changes on sudden contraction head loss coefficients (K-c). Twelve area ratios (sigma) are performed for all zones. Three different Reynolds numbers, remain in laminar flow boundaries, are adopted to determine effects of Reynolds number, as well as location effects. The graphs are constituted by results from computing 48 models for each Reynolds number and the study is concluded with 144 models in the end. In this manner, contraction ratio varying coefficients are obtained for four configurations. According to results, the pressure drop values of the same model for varying contraction locations are different. Maximum values of pressure drops are obtained for the second geometry (G(2)). Combination of maximum pressure drops and minimum velocity values leads to maximum contraction coefficients for G(2). While the area coefficients increase, decreasing values of contraction coefficients of different contraction locations (G) converge in connection with the changing values of velocities and pressure drops. It is necessary to entrain to this remark, for increasing area coefficients. It is stated that K-c-sigma curves vary due to location change. It is recommended to consider the location varying coefficients while modelling different located contracting flows especially for side contracting flows.
FSI ANALYSIS OF SUBMARINE OUTFALL
Gücüyen, E; Erdem, RT; Gökkus, Ü
In the scope of this study, main pipe of the diffuser, risers, ports, internal and external environments forming the discharge system which is used in application are modelled by Finite Elements Analysis (FEA) program to obtain discharge and structural behaviour. The last two spans of the system (20 m) and four ports on these spans are investigated. While the diameter and geometry of the risers and ports remain constant, the diffuser pipe is modelled in three different ways. These are constant sectioned (Model 1), contracting with sharp edge entrance sectioned (Model 2) and gradually contracting sectioned (Model 3) respectively. Among them, only Model 1 is treated as Single Degree of Freedom (SDOF) system and it is simulated by FEA to verify FEA solver in the first place. After structural suitability is confirmed, rest of the models are analysed to determine reaction forces and stresses. The discharge is performed as unsteady external flow as well as steady external flow assumption which is widely used in external flow model in the literature. The discharge analyses are performed in two different ways to verify FEA program. Iterative method is accompanying to FEA program. As a result of this study, proper model for structural and discharge behaviour and external flow effects on discharge velocities are obtained.

Browsing by Author "Gücüyen, E"

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