MCBÜ Açıkerişim Sistemi :: Browsing by Author "Erdem R.T."

Browsing by Author "Erdem R.T."

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Capacity determination of steel frame systems according to artifical neural network analysis
(CI-Premier Pte Ltd, 2011) Erdem R.T.; Seker S.; Gücüyen E.; Bagci M.
Many damages and losses have been occurred after the major scaled earthquakes. Researches have been developed in structural engineering along with other engineering fields with parallel to scientific developments. Determination of collapse safeties of buildings is one of the most efficient ways to observe the behavior of them. Artificial neural networks are computing systems that simulate the biological neural systems of the human brain. Neural Networks types are widely used for engineering problems. Artificial neural network analysis is known as a complex system of the neurons that are connected each other with different influence level. It is composed of a large number of highly interconnected neurons working in unison to solve specific problems. The approach is based on biological models of the human brain's functions. Computation is modeled as a large network of interconnected simple processors and artificial neural network analysis can be trained to recognize input patterns and produce appropriate output responses. The problems that have sufficient training data are suitable for artificial neural network analysis. Prediction of the complex problems and fast evaluation of new examples are the mainly advantages of artificial neural network analysis. In this study, forty steel frame systems which have constant span length and story height are analysed. Earthquake loads are calculated for the frame systems and capacity curves are obtained by using SAP2000 analysis program. The results are evaluated by artificial neural network analysis. The database includes thirty two frames data for training and eight ones for testing the network. Finally the results are compared and given in figures. Suggestions are also proposed.
Structural behaviour of steel lattice towers under wind loads
(CI-Premier Pte Ltd, 2011) Seker S.; Erdem R.T.; Gücüyen E.; Bagci M.
Latticed steel towers are used widely in a variety of civil engineering applications. In this paper, structural behavior of 50 and 75 meters lattice towers which are made of L sectioned frame members under 160km/h wind velocity that causes wind force into structure and have 10m2 square antenna area are investigated. The structures (160-10-50, 160-10-75) are handled in two types as space truss composed of pin-jointed (Model A) and rigid main legs surround space truss composed of pin-jointed (Model B). Wind force is based on Gust Factor and calculated according to EIA-TIA 222-F (Structural Standards Abstract for Steel Antenna Towers & Antenna Supporting Structures) code. The aim of this study is obtaining the effective periods, mass sources, inter story drift ratios, maximum displacements of peak points and maximum frame forces of four structures which have different joint connections and height to determine the safety of them.
Structural behaviour of four legged tubular steel lattice towers under wind loads
(CI-Premier Pte Ltd, 2011) Gücüyen E.; Erdem R.T.; Seker S.; Gökkus U.
Latticed steel towers are widely used in a variety of civil engineering applications. In this paper, structural behavior of 50 and 75 meters lattice towers which are made of tubular sectioned frame members under 160km/h wind velocity that causes wind force into structure and have 10m2 square antenna area are investigated. The structures (160-10-50, 160-10-75) are handled in two types as space truss composed of pin-jointed (Model A) and rigit main legs surround space truss composed of pin-jointed (Model B). Wind force is based on Gust Factor and calculated according to EIA-TIA 222-F (Structural Standards Abstract for Steel Antenna Towers & Antenna Supporting Structures) code. The aim of this study is obtaining the effective periods, mass sources, interstory drift ratios, maximum displacements of peak points and maximum frame forces of four structures which have different joint connections and height to determine the safety of them.
A comparative evaluation of performance based analysis procedures according to 2007 Turkish Earthquake Code and FEMA-440
(Association for Scientific Research, 2011) Erdem R.T.; Baǧci M.; Demir A.
Chapter 7 of the 2007 Turkish Earthquake Code (TEC) entitled "Assessment and Strengthening of Existing Buildings" sets standards for assessment and rehabilitation of existing buildings. Linear elastic and non-linear evaluation procedures of 2007 TEC are applied to reinforced concrete buildings. 2007 TEC gives two methods for assessment and rehabilitation of existing buildings. Linear elastic and non-linear static evaluation procedures are proposed for structural evaluation. A performance-based evaluation methodology is used under three levels of earthquake ground motion intensities with different return periods. The performance acceptance criteria are based on demand to capacity ratios at critical sections for the linear evaluation procedures (equivalent seismic load method and mode superposition method) and material strains for the non-linear evaluation procedures (the non-linear static pushover analysis). Member performance limits are described for three damage levels, considering the anticipated failure mode and ductility capacity of each member. Structural performance is then calculated by accounting for the distribution of member damages over the building.. Consistency between the results of the methods used for seismic evaluation of existing buildings is of prime importance. For this purpose, an irregular structure of in plane (A3 type) and 3 story is considered. The target performance level of the building is obtained by applying the linear and the non-linear evaluation procedures. The results are given comparatively on the target performance level of the building. Furthermore non-linear procedure results are compared between 2007TEC and FEMA-440 Capacity-Spectrum Method (CSM) and Displacement- Coefficient Method (DCM). © Association for Scientific Research.
Nonlinear finite element analysis of impact behavior of concrete beam
(Association for Scientific Research, 2011) Kantar E.; Erdem R.T.; Anil O.
The least well known loading type is the impact loading that are affecting on to RC structures. Several impact tests have been used to demonstrate the relative brittleness and impact resistance of concrete and similar construction materials. However, none of these tests has been declared to be a Standard test, at least in part due to the lack of statistical data on the variation of the results. In this study; total ten beam specimens at which five of them are manufactured from normal concrete compression strength without reinforcement are manufactured. Remaining five had high concrete compression strength. These specimens are tested under the impacts loading that are applied by dropping constant weight hammer from five different heights. The acceleration arises from the impact loading is measured against time. The change of velocity, displacement and energy is calculated for all specimens. The failure modes of the specimens with normal and high concrete compression strength are observed under the loading of constant weight impact hammer that are dropped from different heights. A finite element model that is made by using ABAQUS software is used for the simulation of experiments and model gave compatible results with experiments. © Association for Scientific Research.
Early age corrosion of mild steel in aggressive media
(2012) Ozturk A.U.; Gucuyen E.; Erdem R.T.; Seker S.
Effects of the time of holding, type of section, and concentration of the solution on the early age corrosion of mild steel are studied. Section types for steel specimens were box, tube, and corner. They were subjected to 3.5%, 5.0%, and 7.0% NaCl solutions. It was established that the concentration of the solution affects the corrosion until reaching the saturation value. © 2012 Springer Science+Business Media New York.
Determination of the impact behavior of concrete and reinforced concrete beams
(Association for Scientific Research, 2013) Gücüyen E.; Erdem R.T.; Kantar E.; Baǧci M.
Behavior types of structural members under various loads have been a main field of interest in engineering sciences. There have been several studies performed about determining the behavior of members under tensile, compression, bending and torsion loads until today. However, terrorist attacks and destructive earthquakes have aroused interests of scientists and engineers about solutions of impact problems. In this study, behavior of concrete and reinforced concrete beams under impact loads is investigated. For this purpose, a testing apparatus has been created. Data obtained from experimental study are compared with the analysis results of ABAQUS finite elements program.
Numerical analysis on corrosion resistance of mild steel structures
(2013) Erdem R.T.; Seker S.; Ozturk A.U.; Gucuyen E.
Corrosion resistances of mild steel specimens according to artificial neural network (ANN) analysis were investigated in the scope of this study. Corrosion rate values were taken into numerical analysis as a result of experimental studies under corrosive aggressive media. Mild steel specimens were selected according to the section type varieties such as box, tube and cornier. All steel specimens were subjected to the aggressive media formed using sodium chloride (NaCl with 99.8 % purity) solutions with 3.5, 5.0 and 7.0 % ratios per one liter distilled water and only distilled water. The reduction in corrosion rate has been observed and considered according to some corrosion loss respects. Corrosion rate prediction models were established between corrosion rate and parameters such as mass loss obtained by experimental studies using ANN. ANNs are computing systems that simulate the biological neural systems of the human brain. In this study, ANN analysis was generated to predict the corrosion rate values after experimental studies. Experimental and predicted values were compared by each other and it is seen that a strong relationship was established between them. © 2012 Springer-Verlag London Limited.
Irregular Wave Effects on Dynamic Behavior of Piles
(Springer Verlag, 2013) Gücüyen E.; Erdem R.T.; Gökkuş 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. © 2012 King Fahd University of Petroleum and Minerals.
Corrosion effects on structural behaviour of jacket type offshore structures
(Union of Croatian Civil Engineers and Technicians, 2014) Gucuyen E.; Erdem R.T.
The application of weight losses to investigate corrosion effects on structural behaviour of an offshore structure under wave loads is presented in this study. Weight losses of sections obtained during previous experimental studies are implemented in the model. The jacket type structural model is analysed in its intact and deteriorated forms to demonstrate corrosion effects. The ABAQUS finite elements program is utilized and the fluid structure interaction (FSI) technique is adopted when modelling the interaction between solid and fluid domains. Mode shapes, first three natural frequencies, displacements of selected points, and maximum stresses, are comparatively presented.
Corrosion effects on structural behaviour of jacket type offshore structures; [Utjecaj korozije na izvanobalne konstrukcije]
(Union of Croatian Civil Engineers and Technicians, 2014) Gucuyen E.; Erdem R.T.
The application of weight losses to investigate corrosion effects on structural behaviour of an offshore structure under wave loads is presented in this study Weight losses of sections obtained during previous experimental studies are implemented in the model. The jacket type structural model is analysed in its intact and deteriorated forms to demonstrate corrosion effects. The ABAQUS finite elements program is utilized and the fluid structure interaction (FSI) technique is adopted when modelling the interaction between solid and fluid domains. Mode shapes, first three natural frequencies, displacements of selected points, and maximum stresses, are comparatively presented.
Impact effect on different sized reinforced concrete specimens
(National Institute of Science Communication and Information Resources (NISCAIR), 2015) Erdem R.T.; Gücüyen E.; Kantar E.; Bağcı M.
Behavior of structural members under various loads has been a major interest. However, impact loading type is the least known one among them. Researchers have investigated the behavior of structural members under impact effect recently. For this reason, a well-instrumented experimental program is used to understand the impact behavior of six different sized reinforced concrete specimens. All specimens both have longitudinal and transverse reinforcements. A testing apparatus is developed to perform tests under impact loading. Accelerometers, optic photocells, dynamic force sensor, a data logger and connecting cables are used as well as testing apparatus. Free falling height and mass of steel hammer are taken constant in the study. Test program has been successful to provide several data to understand the impact behavior. Drop numbers and rebound movements of the hammer are determined according to damage situations. Acceleration values are measured from four different points of the specimens. The change of velocity and displacement values is determined for all specimens. Impact force is also measured for each free falling movement and absorbed energy values are calculated according to the area under the curve of impact force-displacement graphs. Test results give substantial information about impact resistances of reinforced concrete members. © 2015, Indian Journal of Engineering and Materials Sciences. All rights reserved.
Improving the impact behavior of pipes using geofoam layer for protection
(Elsevier Ltd, 2015) Anil O.; Erdem R.T.; Kantar E.
In scope of this study performances of protective layers, proposed to protect the pipes from sudden impact loads such as rock falls, are aimed to be compared. In this study, performance, strength and energy absorption capability of geofoam structures against impact forces are investigated by using drop weight impact testing apparatus. Pipes that are manufactured from steel and composite materials are tested with only 130 mm thick sand protecting layer without any geofoam structure, and with two different geofoam with different thicknesses. Results are presented in a comparative form and the effect of geofoam on the impact behavior of sand layer is investigated. Impact load and accelerations on the pipes are measured with respect to time during experiments. Absorbed energy by the pipes are calculated and compared with each other for determining performance of the different protective structures. From the study, it was observed that the sand and geofoam layers used as protective layers were generally successful by reducing the detrimental effects of impact loads in terms of dissipating impact effects on the pipes and the measured acceleration and displacement levels. The best result is obtained from the 50mm thick geofoam with sand layer. Finite elements analyses are performed by using ABAQUS software and both test and analysis results are compared to obtain a model that can give an idea to designers. © 2015 Elsevier Ltd.
Analysis of guyed steel lattice mast subjected to environmental loads; [Analiza čeličnog rešetkastog jarbola izloženog djelovanju vjetra i leda]
(Union of Croatian Civil Engineers and Technicians, 2015) Erdem R.T.
Steel lattice masts rank among the most efficient load-bearing structures in the field of high-rise construction. The non-linear analysis of a guyed steel lattice mast is conducted using the SAP 2000 finite-element program for different ice thickness values at 1500 m of altitude. After definition of the geometrical model and cross-section properties, various load combinations are analysed. Finally, the wind speed - ice thickness relationship is obtained, and the maximum wind speed that the structure can withstand is determined for varying ice thicknesses. © 2015, Union of Croatian Civil Engineers and Technicians. All rights reserved.
Fsi analysis of submarine outfall
(Brodarski Institute, 2016) Gücüyen E.; Erdem R.T.; Gökkuş 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. © 2016, Brodarski Institute. All rights reserved.
Performance evaluation of reinforced concrete buildings with softer ground floors; [Ocjena ponašanja armiranobetonskih zgrada s mekim prizemljem]
(Union of Croatian Civil Engineers and Technicians, 2016) Erdem R.T.
Determination of seismic performance is a significant task in the performancebased seismic analysis of structures. The consistency between analysis results obtained according to various codes is highly significant for seismic evaluation of structures. Non-linear performance of three reinforced concrete buildings having a soft storey irregularity is studied based on the finite elements analysis according to FEMA-356, FEMA-440, and Turkish Earthquake Code - 2007. Damage situations, modal properties, storey drift ratios, and global performance levels are comparatively presented for each structure, and appropriate suggestions are given.
Experimental and numerical investigation of reinforced concrete beams with variable material properties under impact loading
(Elsevier Ltd, 2016) Anil Ö.; Durucan C.; Erdem R.T.; Yorgancilar M.A.
In this study, behaviors of reinforced concrete beams manufactured from several concrete types are experimentally and numerically investigated under dynamic impact loading. In the experimental part of the study, 12 beams manufactured using low strength concrete, normal strength concrete and engineered cementitious composites (ECC) containing polyvinyl alcohol (PVA) fibers are tested under dynamic impact loading. The dimensions of the manufactured reinforced concrete beams are also used as a variable to observe the effect of beam size on the behavior under dynamic impact loading. After the experimental study, finite element analyses of the tested beams are also conducted by using commonly used finite element software to observe the stress distribution under the impact loading. The results obtained from the experimental study illustrated that material type significantly affected the width of the observed cracks on the test specimens. Generally the smallest cracks formed on the test specimens manufactured using ECC and the largest cracks formed on the test specimens manufactured using low strength concrete. The results of the finite element study showed that the crack patterns on the test specimens are in good agreement with the stress distributions obtained from the impact loading simulations. © 2016 Elsevier Ltd
Non-linear analysis of reinforced concrete slabs under impact effect
(Union of Croatian Civil Engineers and Technicians, 2017) Erdem R.T.; Gucuyen 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.
Low-velocity impact behaviour of two way RC slab strengthening with CFRP strips
(Elsevier Ltd, 2018) Yılmaz T.; Kıraç N.; Anil Ö.; Erdem R.T.; Sezer C.
There are a lot of studies focused on behaviour of reinforced concrete (RC) slabs under static and dynamic loadings in the literature. However, investigations related to Carbon Fibre Reinforced Polymer (CFRP) strengthened RC slabs subjected to impact load are still relatively rare. Consequently, an experimental study was performed in order to determine impact behaviour of two way simply supported RC slabs strengthened with CFRP strips. The arrangement and width of CFRP strips were varied in an experimental study. The impact load was applied to slabs using moveable drop-weight test machine designed by the authors. A total of nine RC slabs that were 1000 × 1000 × 80 mm dimensions were manufactured. RC slabs were strengthened using CFRP strips with a width of 50 and 100 mm as orthogonally and diagonally in both one and two directions. One of the specimens was un-strengthened and manufactured as reference specimens. The time-history of the impact force, the accelerations of two points, the center displacement of slabs and the strains of four points on CFRP strips were measured. The crack patterns of slabs are also observed. In the light of experimental results, the effects of applied strengthening method on low-velocity impact behaviour of RC slabs were determined and interpreted. Besides, the finite element models of RC slabs strengthened with CFRP strips are generated using ABAQUS software. It is found out that the proposed finite element model could be used for evaluation of dynamic responses of RC slabs strengthened with CFRP strips subjected to low-velocity impact load. © 2018 Elsevier Ltd
Experimental study on pipe sections against impact loading
(UIKTEN - Association for Information Communication Technology Education and Science, 2018) Gücüyen E.; Erdem R.T.; 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. © 2018 Engin GüCüYEN, R. Tugrul ERDEM, Erkan KANTAR.

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