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Item Non linear vibrations of stepped beam system under different boundary conditions(Techno-Press, 2007) Özkaya E.; Tekin A.In this study, the nonlinear vibrations of stepped beams having different boundary conditions were investigated. The equations of motions were obtained using Hamilton's principle and made non dimensional. The stretching effect induced non-linear terms to the equations. Forcing and damping terms were also included in the equations. The dimensionless equations were solved for six different set of boundary conditions. A perturbation method was applied to the equations of motions. The first terms of the perturbation series lead to the linear problem. Natural frequencies for the linear problem were calculated exactly for different boundary conditions. Second order non-linear terms of the perturbation series behave as corrections to the linear problem. Amplitude and phase modulation equations were obtained. Non-linear free and forced vibrations were investigated in detail. The effects of the position and magnitude of the step, as well as effects of different boundary conditions on the vibrations, were determined.Item Non linear vibrations of stepped beam systems using artificial neural networks(Techno-Press, 2009) Baǧdatli S.M.; Özkaya E.; Özyiǧit H.A.; Tekin A.In this study, the nonlinear vibrations of stepped beams having different boundary conditions were investigated. The equations of motions were obtained by using Hamilton's principle and made non dimensional. The stretching effect induced non-linear terms to the equations. Natural frequencies are calculated for different boundary conditions, stepped ratios and stepped locations by Newton-Raphson Method. The corresponding nonlinear correction coefficients are also calculated for the fundamental mode. At the second part, an alternative method is produced for the analysis. The calculated natural frequencies and nonlinear corrections are used for training an artificial neural network (ANN) program which has a multi-layer, feed-forward, back-propagation algorithm. The results of the algorithm produce errors less than 2.5% for linear case and 10.12% for nonlinear case. The errors are much lower for most cases except clamped-clamped end condition. By employing the ANN algorithm, the natural frequencies and nonlinear corrections are easily calculated by little errors, and the computational time is drastically reduced compared with the conventional numerical techniques.Item Nonlinear vibrations of axially moving beams with multiple concentrated masses Part I: Primary resonance(Techno-Press, 2010) Sarigül M.; Boyaci H.Transverse vibrations of axially moving beams with multiple concentrated masses have been investigated. It is assumed that the beam is of Euler-Bernoulli type, and both ends of it have simply supports. Concentrated masses are equally distributed on the beam. This system is formulated mathematically and then sought to find out approximately solutions of the problem. Method of multiple scales has been used. It is assumed that axial velocity of the beam is harmonically varying around a mean-constant velocity. In case of primary resonance, an analytical solution is derived. Then, the effects of both magnitude and number of the concentrated masses on nonlinear vibrations are investigated numerically in detail.Item Correction of node mapping distortions using universal serendipity elements in dynamical problems(Techno-Press, 2011) Küçükarslan S.; Demir A.In this paper, the use of universal serendipity elements (USE) to eliminate node mapping distortions for dynamic problem is presented. Rectangular shaped elements for USE are being introduced by using a flexible master element with an adjustable edge node location. The shape functions of the universal serendipity formulation are used to derive the mass and damping matrices for the dynamic analyses. These matrices eliminate the node mapping distortion errors that occurs incase of the standard shape function formulations. The verification of new formulation will be tested and the errors encountered in the standard formulation will be studied for a dynamically loaded deep cantilever.Item Vibrations of an axially accelerating, multiple supported flexible beam(Techno-Press, 2012) Kural S.; Özkaya E.In this study, the transverse vibrations of an axially moving flexible beams resting on multiple supports are investigated. The time-dependent velocity is assumed to vary harmonically about a constant mean velocity. Simple-simple, fixed-fixed, simple-simple-simple and fixed-simple-fixed boundary conditions are considered. The equation of motion becomes independent from geometry and material properties and boundary conditions, since equation is expressed in terms of dimensionless quantities. Then the equation is obtained by assuming small flexural rigidity. For this case, the fourth order spatial derivative multiplies a small parameter; the mathematical model converts to a boundary layer type of problem. Perturbation techniques (The Method of Multiple Scales and The Method of Matched Asymptotic Expansions) are applied to the equation of motion to obtain approximate analytical solutions. Outer expansion solution is obtained by using MMS (The Method of Multiple Scales) and it is observed that this solution does not satisfy the boundary conditions for moment and incline. In order to eliminate this problem, inner solutions are obtained by employing a second expansion near the both ends of the flexible beam. Then the outer and the inner expansion solutions are combined to obtain composite solution which approximately satisfying all the boundary conditions. Effects of axial speed and flexural rigidity on first and second natural frequency of system are investigated. And obtained results are compared with older studies.Item An improved particle swarm optimizer for steel grillage systems(Techno-Press, 2013) Erdal F.; Doǧan E.; Saka M.P.In this paper, an improved version of particle swarm optimization based optimum design algorithm (IPSO) is presented for the steel grillage systems. The optimum design problem is formulated considering the provisions of American Institute of Steel Construction concerning Load and Resistance Factor Design. The optimum design algorithm selects the appropriate W-sections for the beams of the grillage system such that the design constraints are satisfied and the grillage weight is the minimum. When an improved version of the technique is extended to be implemented, the related results and convergence performance prove to be better than the simple particle swarm optimization algorithm and some other meta-heuristic optimization techniques. The efficiency of different inertia weight parameters of the proposed algorithm is also numerically investigated considering a number of numerical grillage system examples. Copyright © 2013 Techno-Press, Ltd.Item Vibration measurement and vulnerability analysis of a power plant cooling system(Techno-Press, 2013) Anil O.; Akbaş S.O.; Kantar E.; Cem Gel A.During the service life of a structure, design complications and unexpected events may induce unforeseen vibrations. These vibrations can be generated by malfunctioning machinery or machines that are modified or placed without considering the original structural design because of a change in the intended use of the structure. Significant vibrations occurred at a natural gas plant cooling structure during its operation due to cavitation effect within the hydraulic system. This study presents findings obtained from the in-situ vibration measurements and following finite-element analyses of the cooling structure. Comments are made on the updated performance level and damage state of the structure using the results of these measurements and corresponding numerical analyses. An attempt was also made to assess the applicability of traditional displacement-based vulnerability estimation methods in the health monitoring of structures under vibrations with a character different from those due to seismic excitations.Item Strengthening of RC beams with prefabricated RC U cross-sectional plates(Techno-Press, 2014) Demir A.; Tekin M.; Turali T.; Bagci M.The topic of this study is to strengthen cracked beams with prefabricated RC U cross-sectional plates. The damaged beams were repaired by epoxy based glue. The repaired beams were strengthened using prefabricated plates. The strengthening plates were bonded to the bottom and side faces of the beams by anchorage rods and epoxy. The strengthened beams were incrementally loaded up to maximum load capacities. The experimental results were satisfactory since the load carrying capacities of damaged beams were increased approximately 76% due to strengthening. It was observed that strengthening plates had a dominant effect on the performance of beams in terms of both the post-elastic strength enhancement and the ductility. The experimental program was supported by a three-dimensional nonlinear finite element analysis. The experimental results were compared with the results obtained from the beam modeled with ANSYS finite element program. Copyright © 2014 Techno-Press, Ltd.Item Prediction of acceleration and impact force values of a reinforced concrete slab(Techno-Press, 2014) Tuʇrul Erdem R.Concrete which is a composite material is frequently used in construction works. Properties and behavior of concrete are significant under the effect of different loading cases. Impact loading which is a sudden dynamic one may have destructive effects on structures. Testing apparatuses are designed to investigate the impact effect on test members. Artificial Neural Network (ANN) is a computational model that is inspired by the structure or functional aspects of biological neural networks. It can be defined as an emulation of biological neural system. In this study, impact parameters as acceleration and impact force values of a reinforced concrete slab are obtained by using a testing apparatus and essential test devices. Afterwards, ANN analysis which is used to model different physical dynamic processes depending on several variables is performed in the numerical part of the study. Finally, test and predicted results are compared and it's seen that ANN analysis is an alternative way to predict the results successfully. Copyright © 2014 Techno-Press, Ltd.Item Solving design optimization problems via hunting search algorithm with Levy flights(Techno-Press, 2014) Doʇan E.This study presents a hunting search based optimum design algorithm for engineering optimization problems. Hunting search algorithm is an optimum design method inspired by group hunting of animals such as wolves, lions, and dolphins. Each of these hunters employs hunting in a different way. However, they are common in that all of them search for a prey in a group. Hunters encircle the prey and the ring of siege is tightened gradually until it is caught. Hunting search algorithm is employed for the automation of optimum design process, during which the design variables are selected for the minimum objective function value controlled by the design restrictions. Three different examples, namely welded beam, cellular beam and moment resisting steel frame are selected as numerical design problems and solved for the optimum solution. Each example differs in the following ways: Unlike welded beam design problem having continuous design variables, steel frame and cellular beam design problems include discrete design variables. Moreover, while the cellular beam is designed under the provisions of BS 5960, LRFD-AISC (Load and Resistant Factor Design-American Institute of Steel Construction) is considered for the formulation of moment resisting steel frame. Levy Flights is adapted to the simple hunting search algorithm for better search. For comparison, same design examples are also solved by using some other well-known search methods in the literature. Results reveal that hunting search shows good performance in finding optimum solutions for each design problem. Copyright © 2014 Techno-Press, Ltd.Item Prediction of Hybrid fibre-added concrete strength using artificial neural networks(Techno-Press, 2015) Demir A.Fibre-added concretes are frequently used in large site applications such as slab and airports as well as in bearing system elements or prefabricated elements. It is very difficult to determine the mechanical properties of the fibre-added concretes by experimental methods in situ. The purpose of this study is to develop an artificial neural network (ANN) model in order to predict the compressive and bending strengths of hybrid fibre-added and non-added concretes. The strengths have been predicted by means of the data that has been obtained from destructive (DT) and non-destructive tests (NDT) on the samples. NDTs are ultrasonic pulse velocity (UPV) and Rebound Hammer Tests (RH). 105 pieces of cylinder samples with a dimension of 150 × 300 mm, 105 pieces of bending samples with a dimension of 100×100×400 mm have been manufactured. The first set has been manufactured without fibre addition, the second set with the addition of %0.5 polypropylene and %0.5 steel fibre in terms of volume, and the third set with the addition of %0.5 polypropylene, %1 steel fibre. The water/cement (w/c) ratio of samples parametrically varies between 0.3-0.9. The experimentally measured compressive and bending strengths have been compared with predicted results by use of ANN method. Copyright © 2015 Techno-Press, Ltd.Item Free vibration analysis of axially moving beam under non-ideal conditions(Techno-Press, 2015) Baʇdatli S.M.; Uslu B.In this study, linear vibrations of an axially moving beam under non-ideal support conditions have been investigated. The main difference of this study from the other studies; the non-ideal clamped support allow minimal rotations and non-ideal simple support carry moment in minimal orders. Axially moving Euler-Bernoulli beam has simple and clamped support conditions that are discussed as combination of ideal and non-ideal boundary with weighting factor (k). Equations of the motion and boundary conditions have been obtained using Hamilton's Principle. Method of Multiple Scales, a perturbation technique, has been employed for solving the linear equations of motion. Linear equations of motion are solved and effects of different parameters on natural frequencies are investigated. Copyright © 2015 Techno-Press, Ltd.Item Experimental and numerical investigation of walls strengthened with fiber plaster(Techno-Press, 2015) Başaran H.; Demir A.; Baʇci M.; Ergun S.The topic of this study is to investigate behaviors of masonry walls strengthened with reinforced fiber plaster under diagonal tensile loads. Full blend brick 100×50×30 mm in dimensions were used to make masonry walls with dimensions of 400×400×100 mm. Three different samples were manufactured by plastering masonry walls with traditional style, with 3% polypropylene or with 5% steel fiber. All the samples were tested using ASTM 1391- 81 standards. The propagation of damage on samples caused by diagonal tensile load was observed and load-displacement graphs were plotted for each sample. A finite element software (ABAQUS) was used to obtain numerical values for all samples and crack patterns and load-displacement responses were obtained. Experimental and numerical results were compared. Copyright © 2015 Techno-Press, Ltd.Item Non-linear transverse vibrations of tensioned nanobeams using nonlocal beam theory(Techno-Press, 2015) Baʇdatli S.M.In this study, nonlinear transverse vibrations of tensioned Euler-Bernoulli nanobeams are studied. The nonlinear equations of motion including stretching of the neutral axis and axial tension are derived using nonlocal beam theory. Forcing and damping effects are included in the equations. Equation of motion is made dimensionless via dimensionless parameters. A perturbation technique, the multiple scale methods is employed for solving the nonlinear problem. Approximate solutions are applied for the equations of motion. Natural frequencies of the nanobeams for the linear problem are found from the first equation of the perturbation series. From nonlinear term of the perturbation series appear as corrections to the linear problem. The effects of the various axial tension parameters and different nonlocal parameters as well as effects of different boundary conditions on the vibrations are determined. Nonlinear frequencies are estimated; amplitude-phase modulation figures are presented for simple-simple and clamped-clamped cases. © 2015 Techno-Press, Ltd.Item Effect of model calibration on seismic behaviour of a historical mosque(Techno-Press, 2016) Demir A.; Nohutcu H.; Ercan E.; Hokelekli E.; Altintas G.The objective of the study is to investigate the effects of model calibration on seismic behaviour of a historical mosque which is one of the most significant Ottomon structures. Seismic analyses of calibrated and noncalibrated numeric models were carried out by using acceleration records of Kocaeli earthquake in 1999. In numerical analysis, existing crack zones on real structure was investigated in detail. As a result of analyses, maximum stresses and displacements of calibrated and noncalibrated numerical models were compared each other. Consequently, seismic behaviour and damage state of historical masonry Hafsa Sultan mosque was determined as more realistic in the event of a severe earthquake. Copyright © 2016 Techno-Press, Ltd.Item Collapse mechanism estimation of a historical slender minaret(Techno-Press, 2017) Nohutcu H.; Hokelekli E.; Ercan E.; Demir A.; Altintas G.The aim of this study is to accurately estimate seismic damage and the collapse mechanism of the historical stone masonry minaret "Hafsa Sultan", which was built in 1522. Surveying measurements and material tests were conducted to obtain a 3D solid model and the mechanical properties of the components of the minaret. The initial Finite Element (FE) model is analyzed and numerical dynamic characteristics of the minaret are obtained. The Operational Modal Analysis (OMA) method is conducted to obtain the experimental dynamic characteristics of the minaret and the initial FE model is calibrated by using the experimental results. Then, linear time history (LTH) and nonlinear time history (NLTH) analyses are carried out on the calibrated FE model by using two different ground motions. Iron clamps which used as connection element between the stones of the minaret considerably increase the tensile strength of the masonry system. The Concrete Damage Plasticity (CDP) model is selected in the nonlinear analyses in ABAQUS. The analyses conducted indicate that the results of the linear analyses are not as realistic as the nonlinear analysis results when compared with existing damage. Copyright © 2017 Techno-Press, Ltd.Item Vibration analysis of a beam on a nonlinear elastic foundation(Techno-Press, 2017) Karahan M.M.F.; Pakdemirli M.Nonlinear vibrations of an Euler-Bernoulli beam resting on a nonlinear elastic foundation are discussed. In search of approximate analytical solutions, the classical multiple scales (MS) and the multiple scales Lindstedt Poincare (MSLP) methods are used. The case of primary resonance is investigated. Amplitude and phase modulation equations are obtained. Steady state solutions are considered. Frequency response curves obtained by both methods are contrasted with each other with respect to the effect of various physical parameters. For weakly nonlinear systems, MS and MSLP solutions are in good agreement. For strong hardening nonlinearities, MSLP solutions exhibit the usual jump phenomena whereas MS solutions are not reliable producing backward curves which are unphysical. Copyright © 2017 Techno-Press, Ltd.Item Estimation of impact characteristics of RC slabs under sudden loading(Techno-Press, 2021) Erdem R.T.Reinforced concrete (RC) slabs are exposed to several static and dynamic effects during their period of service. Accordingly, there are many studies focused on the behavior of RC slabs under these effects in the literature. However, impact loading which can be more effective than other loads is not considered in the design phase of RC slabs. This study aims to investigate the dynamic behavior of two-way RC slabs under sudden impact loading. For this purpose, 3 different simply supported slab specimens are manufactured. These specimens are tested under impact loading by using the drop test setup and necessary measurement devices such as accelerometers, dynamic load cell, LVDT and data-logger. Mass and drop height of the hammer are taken constant during experimental study. It is seen that rigidity of the specimens effect experimental results. While acceleration values increase, displacement values decrease as the sizes of the specimens have bigger values. In the numerical part of the study, artificial neural networks (ANN) analysis is utilized. ANN analysis is used to model different physical dynamic processes depending upon the experimental variables. Maximum acceleration and displacement values are predicted by ANN analysis. Experimental and numerical values are compared and it is found out that proposed ANN model has yielded consistent results in the estimation of experimental values of the test specimens. © 2021 Techno-Press, Ltd.Item Magnetic field effect on nonlinear vibration of nonlocal nanobeam embedded in nonlinear elastic foundation(Techno-Press, 2021) Yapanmiş B.E.; Toǧun N.; Baǧdatli S.M.; Akkoca Ş.The history of modern humanity is developing towards making the technological equipment used as small as possible to facilitate human life. From this perspective, it is expected that electromechanical systems should be reduced to a size suitable for the requirements of the era. Therefore, dimensionless motion analysis of beams on the devices such as electronics, optics, etc., is of great significance. In this study, the linear and nonlinear vibration of nanobeams, which are frequently used in nanostructures, are focused on. Scenarios have been created about the vibration of nanobeams on the magnetic field and elastic foundation. In addition to these, the boundary conditions (BC) of nanobeams having clamped-clamped and simple-simple support situations are investigated. Nonlinear and linear natural frequencies of nanobeams are found, and the results are presented in tables and graphs. When the results are examined, decreases the vibration amplitudes with the increase of magnetic field and the elastic foundation coefficient. Higher frequency values and correction terms were obtained in clamped-clamped support conditions due to the structure's stiffening. © 2021 Techno-Press, Ltd.Item Effect of infill wall properties on seismic response of RC structures(Techno-Press, 2021) Demir A.; Cengiz M.M.Brick infill walls (BIW) have significant effects on reinforced concrete (RC) structures’ seismic performances. However, mechanical effects on the structural performance of BIWs, which are regarded as only weight at the design stage, are not considered in many seismic codes. Therefore, seismic performances of new and existing RC structures could not be realistically obtained. This study aims to investigate the effects on the structural behavior of BIWs, stucco types, and soft story. RC structures with and without BIWs are modeled by using the SAP2000 program. BIW is modeled with the equivalent diagonal compression strut method, and mechanical properties of BIWs plastered with conventional and polypropylene fibrous stuccos are taken from literature. Seismic performances of all structures are investigated using the pushover analysis method, according to Turkish Seismic Code-2007 (TSC-2007) principles. Besides, natural periods, rigidities, ductilities and energy dissipation capacities of all structures are obtained. As a result of analyses, it is determined that BIWs have significant effects on structural performances in terms of rigidity and ductility, and fibrous stucco considerably increases RC structures’ rigidity and ductility. These walls can even lead to the collapse of structures in severe earthquakes if design engineers don’t regard BIWs or BIWs are placed as asymmetric or deficient on the structure. Copyright © 2021 Techno-Press, Ltd.