• Journal of the Society of Naval Architects of Korea
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• v.44 no.3 s.153
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• pp.314-322
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• 2007

In general, the vibration and structural analyses have been carried out by using each finite element model separately because of different size of finite element mesh and different focusing area of each analysis. In some cases, however, it is required to perform both global vibration and structural analyses at the same time using a finite element model for global structural analysis, which asks for a special treatment for a vibration analysis. In this study, a technique to perform a global vibration analysis using a finite element model for a global structural analysis has been developed and its effectiveness has been verified by its application to a whole ship.

• Earthquakes and Structures
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• v.22 no.3
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• pp.289-304
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• 2022

During strong ground motions, adjacent structures with insufficient separation distances collide with each other causing considerable architectural and structural damage or collapse of the whole structure. Generally, existing design procedures for determining the separation distance between adjacent buildings subjected to structural pounding are based on approximations of the buildings' peak relative displacement. These procedures are based on unknown safety levels. This paper attempts to evaluate the influence of foundation flexibility on the structural seismic response by considering the variability in the system and uncertainties in the ground motion characteristics through comprehensive numerical simulations. Actually, the aim of this study is to evaluate the influence of foundation flexibility on probabilistic evaluation of structural pounding. A Hertz-damp pounding force model has been considered in order to effectively capture impact forces during collisions. In total, 5.25 million time-history analyses were performed over the adopted models using an ensemble of 25 ground motions as seismic input within OpenSees software. The results of the study indicate that the soil-structure interaction significantly influences the pounding-involved responses of adjacent structures during earthquakes and generally increases the pounding probability.

• Computers and Concrete
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• v.20 no.4
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• pp.409-418
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• 2017

Turkey owns a very important cultural and historical heritage that bears the traces of thousands of years of culture and civilization. It is an inevitable duty to carry these treasuries to the future generations. In this paper, structural safety assessment and strengthening stages of one of these important historical heritages namely Amasya Taşhan was investigated in details as a case study. For this purpose, the detailed architectural projects of the structure with the information of all load carrying and structural elements were prepared. Then, the structural dynamic analyses were performed by using SAP2000. The internal forces obtained from the dynamic analyses determined the weak regions. By obtaining the information from dynamic analyses, the method of state of the art technique of application of the structure that needs structural strengthening was selected. The last step is the application of these precautions to the whole structure. At the end of this study, this study not also contains several strengthening techniques that is used in one masonry structure together but also provides a useful reference to the practicing engineers.

• Steel and Composite Structures
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• v.17 no.4
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• pp.405-429
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• 2014

In this paper, it is aimed to determine the structural behavior of suspension bridges considering construction stages and different soil conditions. Bosporus Suspension Bridge connecting the Europe and Asia in Istanbul is selected as an example. Finite element model of the bridge is constituted using SAP2000 program considering existing drawings. Geometric nonlinearities are taken into consideration in the analysis using P-Delta large displacement criterion. The time dependent material strength of steel and concrete and geometric variations is included in the analysis. Time dependent material properties are considered as compressive strength, aging, shrinkage and creep for concrete, and relaxation for steel. To emphases the soil condition effect on the structural behavior of suspension bridges, each of hard, medium and soft soils are considered in the analysis. The structural behavior of the bridge at different construction stages and different soil conditions has been examined. Two different finite element analyses with and without construction stages are carried out and results are compared with each other. At the end of the analyses, variation of the displacement and internal forces such as bending moment, axial forces and shear forces for bridge deck and towers are given in detail. Also, displacement and stresses for bridge foundation are given with detail. It can be seen from the analyses that there are some differences between both analyses (with and without construction stages) and the results obtained from the construction stages are bigger. It can be stated that the analysis without construction stages cannot give the reliable solutions. In addition, soil condition have effect on the structural behavior of the bridge. So, it is thought that construction stage analysis using time dependent material properties, geometric nonlinearity and soil conditions effects should be considered in order to obtain more realistic structural behavior of suspension bridges.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.71-78
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• 2005

In performance-based design methods, it is clear that the evaluation of the nonlinear response is required. The methods available to the design engineer today are nonlinear tim history analyses, or monotonic static nonlinear analyses, or equivalent static analyses with simulated inelastic influences. The nonlinear time analysis is the most accurate method in computing the nonlinear response of structures, but it is time-consuming and necessitate more efforts. Some codes proposed the capacity spectrum method based on the nonlinear static analysis to determine earthquake-induced demand given the structure pushover curve. This procedure is conceptually simple but iterative and time consuming with some errors. The nonlinear direct spectrum method is proposed and studied to evaluate nonlinear response of structures, without iterative computations, given by the structural linear vibration period and yield strength from the pushover analysis. The purpose of this paper is to compare the accuracy and the reliability of approximate nonlinear methods with respect to RC dual system and various earthquakes.

• Architectural research
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• v.10 no.1
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• pp.1-11
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• 2008

A Steel column with damaged spray-applied fire resistive material (SFRM) may exhibit reduced structural performance due to the effects of elevated temperature during fire events. Thus, the fire load behavior of steel columns with removed or reduced SFRM needs to be examined to predict the structural damage by fire. FEM analyses were performed for the flange thinning removal models in which the SFRM was reduced as a constant strip in thickness at the top flange of the column. The temperature results for all models obtained from the heat transfer analyses were included as an initial condition in the FEM structural analyses. In this study, the results of analysis show that even small remnants of SFRM led to an effective reduction of temperature at any given fire duration, and improved significantly the axial load capacity of a column as compared to the complete removal cases of SFRM.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.607-613
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• 2011

In this study, structural vibration analyses for a 5MW offshore wind wind-turbine model have been performed for different substructure models. The efficient equivalent modeling method based on computational multi-body dynamics are applied to the finite element models of the present offshore wind turbines. Monopile and tri-pod substructure types of the typical offshore wind-turbine are considered herein. Detailed finite element modeling concepts and boundary conditions are described and the comparison results for previous analyses are presented in order to show the verification of the present numerical approach. Campbell diagrams are also present to investigate the rotational resonance characteristics of the offshore wind-turbines with different substructures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.04a
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• pp.183-190
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• 1993

The seismic response of the reactor structures depends on the dynamic charact-eristics of the structures and the input earthquake loadings. The stuctural integ-rity of the reactor internal components can be verified by the dynamic response analyses to implement the effects of the design loadings like earthquakes. The sensitivity analyses of the dynamic characteristics for the analytical model of reactor structures considering the possible variations of the stiffnesses of the CSB upper flange and the snubber were performed to improve the dynamic characteri-stics of the structures against seismic loading. And to enhance the structural design margin of the reactor internal components the nonlinear time history analyses were attempted for the modified analytical model, and the results were compared between the reference model and the modified ones.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.05a
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• pp.159-163
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• 1999

A seat frame structure in automotive vehicles made of polymer matrix composite to achieve weight reduction at low cost was developed. In order to design and manufacture the actual product, studies on material selection, and structural analyses were performed. Structural analyses were performed with a finite element analysis. Analyses were done for several cases suggested in various safety regulations of FMVSS(Federal Motor Vehicle Safety Standards). Each result was utilized to modify the actual shape to obtain a lighter, safer and more stable design. The final design was used to produce a sample bottom plate of the seat structure. Substitution of the material resulted in a weight reduction effect with equivalent strength, fatigue and impact characteristics. Furthermore, several effects from the replacement of the material besides weight reduction were also examined.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.53-60
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• 2002

It has been recognized that damage control must become a more explicit design consideration. In an effort to develop design methods based on performance it is clear that the evaluation of the inelastic response is required. The methods available to the design engineer today are nonlinear time history analyses, or monotonic static nonlinear analyses, or equivalent static analyses with simulated inelastic influences. Some codes proposed the capacity spectrum method based on the nonlinear static(pushover) analysis to determine earthquake-induced demand given the structure pushover curve. This procedure is conceptually simple but iterative and time consuming with some errors. This paper presents a nonlinear direct spectrum method to evaluate seismic Performance of structure, without iterative computations, given the structural initial elastic period and yield strength from the pushover analysis, especially for multi degree of freedom structures. The purpose of this paper is to investigate accuracy and confidence of this method from a point of view of various earthquakes and unloading stiffness degradation parameters.