Browsing by Subject "Nonlinear analysis"
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Item Transient dynamic analysis of dam-reservoir interaction by coupling DRBEM and FEM(2004) Küçükarslan S.; Coşkun S.B.In this paper, time domain dynamic analysis of dam-reservoir interaction is presented by coupling the dual reciprocity boundary element method in the infinite fluid domain and the finite element method in the solid domain. An efficient coupling procedure is formulated by using sub-structuring method. Sammerfeld's boundary condition for far end of the infinite domain is implemented. To verify the proposed scheme, numerical examples are carried out to compare with the available exact solutions and results of the finite-finite element coupling.Item Comparison of nonlinear static and dynamic analyses on a R/C building(Association for Scientific Research, 2013) Tekin M.; Gürbüz A.; Demir A.In recent years, nonlinear calculation methods can be easily carried out by means of developing computer technologies. In this way, comparisons of the nonlinear methods have started to increase rapidly and more studies are carried out on regular and irregular buildings. However, it is most important to compare consistency of the methods on buildings. In this study, most common nonlinear static (pushover) and nonlinear dynamic analysis (time history analysis) methods were compared on an asymmetric planned reinforced concrete (R/C) building. Building having horizontal and vertical irregularities was 5-story. Analyses were carried out by using SAP2000 program. The results are discussed in terms of base shear, lateral displacements and top displacement ratios.Item Effect of Hysteretic Models on Seismic Behavior of Existing RC Structures(American Society of Civil Engineers (ASCE), 2015) Ergun S.; Demir A.The aim of this study is to investigate the effect of hysteretic models on displacement demands of reinforced concrete (RC) structures having various irregularities and determine more proper hysteretic models for different types of RC structures. The RC structures having irregularities such as soft story and overhang were analyzed with nonlinear pushover and nonlinear time-history methods. Concrete compressive strength, stirrup amount, and the number of stories for the structures were variable parameters. Totally, 25,664 analyses were carried out. Displacement capacities and performance levels of structures were determined using nonlinear pushover analysis. Exceedance ratios of performance levels and displacements demanded from the structures of 100 severe ground motions that occurred worldwide were obtained using nonlinear time-history analysis (NTHA). In NTHA, various hysteretic models were used to define inelastic behavior of RC structures. The analyses show that the hysteretic models have a significant effect on displacement demands of RC structures. Finally, proper hysteretic models are suggested according to the type of structure and purpose of occupancy. © 2014 American Society of Civil Engineers.Item Nonlinear vibration of a nanobeam on a pasternak elastic foundation based on non-local euler-bernoulli beam theory(MDPI AG, 2016) Togun N.; Baǧdatli S.M.In this study, the non-local Euler-Bernoulli beam theory was employed in the nonlinear free and forced vibration analysis of a nanobeam resting on an elastic foundation of the Pasternak type. The analysis considered the effects of the small-scale of the nanobeam on the frequency. By utilizing Hamilton's principle, the nonlinear equations of motion, including stretching of the neutral axis, are derived. Forcing and damping effects are considered in the analysis. The linear part of the problem is solved by using the first equation of the perturbation series to obtain the natural frequencies. The multiple scale method, a perturbation technique, is applied in order to obtain the approximate closed solution of the nonlinear governing equation. The effects of the various non-local parameters, Winkler and Pasternak parameters, as well as effects of the simple-simple and clamped-clamped boundary conditions on the vibrations, are determined and presented numerically and graphically. The non-local parameter alters the frequency of the nanobeam. Frequency-response curves are drawn. © 2016 by the authors; licensee MDPI, Basel, Switzerland.Item Stability of fluid conveying nanobeam considering nonlocal elasticity(Elsevier Ltd, 2017) Bağdatli S.M.; Togun N.In this study, the nonlocal Euler–Bernoulli beam theory is employed in the vibration and stability analysis of a nanobeam conveying fluid. The nanobeam is assumed to be traveling with a constant mean velocity along with a small harmonic fluctuation. In the considered analysis, the effects of the small-scale of the nanobeam are incorporated into the equations. By utilizing Hamilton's principle, the nonlinear equations of motion including stretching of the neutral axis are derived. Damping effect is considered in the analysis. The closed form approximate solution of nonlinear equations is solved by using the multiple scale method, a perturbation technique. The effects of the different value of the nonlocal parameters, mean speed value and ratios of fluid mass to the total mass as well as effects of the simple–simple and clamped–clamped boundary conditions on the linear and nonlinear frequencies, stability, frequency–response curves and bifurcation point are presented numerically and graphically. The solvability conditions are obtained for the three distinct cases of velocity fluctuation frequency. For all cases, the stability areas of system are constructed analytically. © 2017 Elsevier LtdItem 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 Collapse mechanism estimation of a historical masonry minaret considered soil-structure interaction(Techno-Press, 2021) Altıok T.Y.; Demir A.Cultures and lifestyles of past communities can be transferred to the next generations through historical structures. Accordingly, these structures should be carefully preserved against devastating events i.e. earthquakes, wind, and fire. Seismic performances of historical structures can be determined with destructive and nondestructive methods. As destructive methods are quite difficult and complex, easier and reliable methods should be used to determine the seismic behaviors of these structures. In this study, the seismic behavior of the historical Lala Mehmet Pasha minaret is investigated by considering Soil-Structure Interaction (SSI). Dynamical properties of the minaret are experimentally obtained with the operational modal analysis (OMA) method and the initial finite element (FE) model is updated. Embedded and SSI models are generated by Abaqus, then linear (LTH) and nonlinear time history (NLTH) analyses are performed. As a result of analyses, displacements, damage, and stress distributions are obtained and interpreted. These analyses show that SSI is quite effective on the structural behavior and results obtained from the nonlinear analysis are more realistic than that of linear analysis. © 2021 Techno-Press, Ltd.Item A new characteristic numerical approach with evolutionary residual error analysis to nonlinear boundary value problems occurring in heat and mass transfer via combinatoric Mittag-Leffler polynomial(Taylor and Francis Ltd., 2022) Kürkçü Ö.K.; Sezer M.This study focuses on new numerical approach to the solutions of nonlinear boundary value problems occurring in heat and mass transfer, constructing a matrix-combinatorial method collocated by the Chebyshev-Lobatto points and based on the Mittag-Leffler polynomial. For the first time, a matrix-collocation method is coupled with a combinatoric polynomial. In view of this combination, the method converts the linear and nonlinear terms to the matrix forms and then gathers them to a fundamental matrix equation. In addition to the novelty, an inventive nonlinear residual error analysis of general type is firstly theorized and adapted for improving the solutions to the problems in question and also, it allows to regard the nonlinear terms as an operator in calculations. The obtained solutions are thereby corrected. Numerical and graphical illustrations are provided to scrutinize the accuracy, productivity and comparability of the method. Upon evaluations of all these tasks, one can admit that the method is comprehensible, consistent and easily programmable. © 2022 Taylor & Francis Group, LLC.Item Excessive snow induced steel roof failures in Turkey(Elsevier Ltd, 2022) Korkmaz H.H.; Dere Y.; Özkılıç Y.O.; Bozkurt M.B.; Ecemiş A.S.; Özdoner N.In January 2017, collapses of the numerous roofs were reported due to excessive snowfall in many provinces of Turkey. In this study, the reasons behind the collapses of the steel roofs of 19 factory buildings were investigated. The steel roofs supported by the precast reinforced concrete columns indicated a similar collapse pattern to each other under the unexpected heavy snow loading. The failure mechanisms of the roofs under the snow loading were simulated numerically. Nonlinear finite element models of a typical industrial building were developed and analyzed under an incremental vertical loading that is identical to snow loading. As a result of the analysis, the vertical load carrying capacity of the roof system and the snow load level causing the collapse of roof were determined. The resulting snow load was compared with the snow load values provided by the code specifications. In addition, the collapse mechanism of the steel roof system was analytically determined and compared with the collapse modes observed in the field and the causes of the failure were evaluated. The failure mechanism and the buckling modes obtained from analyses were found very similar to those observed during the site inspections. The main reasons of the roof failures may be attributed to excessive amount of snow caused by climate change and discrepancy of designed project and as-built project due to lack of building inspection control during the construction of the buildings. © 2022 Elsevier LtdItem Investigation of the effect of damper location and slip load calculation on the behavior of a RC structure(Techno-Press, 2023) Şevik M.; Altıok T.Y.; Demir A.Energy dissipation systems increase the energy dissipation capacity of buildings considerably. In this study, the effect of dampers on a typical 10-storey reinforced concrete structure with a ductile moment-resisting frame was investigated. In this context, 5 different models were created according to the calculation of the slip load and the positions of the dampers in the structure. Nonlinear time-history analyzes using 11 different earthquake acceleration records were performed on the models using the ETABS program. As a result of the analyses, storey displacements, energy dissipation ratios, drift ratios, storey accelerations, storey shears, and hysteretic curves of the dampers on the first and last storey and overturning moments are presented. In the study, it was determined that friction dampers increased the energy dissipation capacities of all models. In addition, it has been determined that positioning the dampers in the outer region of the structures and taking the base shear as a basis in the slip load calculation will be more effective. © 2023 Techno-Press, Ltd.Item Investigation of impact behavior of shear deficient RC beams using nonlinear FEA(Taylor and Francis Ltd., 2024) Yılmaz T.; Erdem R.T.; Kıshı N.; Anıl Ö.In the scope of this study, the impact behavior of shear deficient RC beam was investigated by performing numerical analysis based on the finite element method and comparing it with the experimental results. The explicit dynamic analysis of 27 shear-deficient RC beams of which experiments were previously carried out by one of the authors has been conducted by utilizing ABAQUS software, and also it is aimed to establish the reasonable finite element model that is accordant with the experimental results. The variables of the experimental study were the ratio of longitudinal reinforcement on the tension side of the member, the shear-span ratio, and impact velocities. The time histories of impact load, reaction forces on supports, and the displacements measured from the mid-span of the beams were recorded during the experiments, and the energy absorption capacities of RC beams were evaluated based on an area enclosed by the impact load vs. displacement loops. It is investigated and interpreted to what extent the proposed nonlinear finite element method could be successful for analyzing the values of impact load and mid-span displacements and to what extent the explicit dynamic solution technique could be successful for simulating experiments. It is found that the maximum differences between the results obtained by numerical analysis using ABAQUS and the experimental results are 7% and 14% for impact loads and mid-span displacements, respectively. © 2022 Taylor & Francis Group, LLC.