• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.10a
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• pp.207-215
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• 1993

With the aid of finite element method, this paper deals with the problem of structural response variability of transmission tower subjected to the spatial variability of material properties, Young's modulus herein. The spatial variability of material property are modeled as two-dimensional stochastic field which has an isotropic auto-correlation function. Response variability has been computed based on two numerical techniques, such as the Neumann expansion method in conjunction with the Monte Carlo simulation method. The results by these numerical methods are compared with those by the deterministic approach.

• Structural Engineering and Mechanics
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• v.48 no.1
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• pp.1-16
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• 2013

The seismic response of RC space frame structures with isolated footing resting on a shallow soil stratum on rock is presented in this paper. Homogeneous soil stratum of different stiffness in the very soft to stiff range is considered. Soil, footing and super structure are considered to be the parts of an integral system. A finite element model of the integrated system is developed and subjected to scaled acceleration time histories recorded during two different real earthquakes. Dynamic analysis is performed using mode superposition method of transient analysis. A parametric study is conducted to investigate the effect of flexibility of soil in the dynamic behaviour of low-rise building frames. The time histories and Fourier spectra of roof displacement, base shear and structural response quantities of the space frame on compliant base are presented and compared with the fixed base condition. Results indicate that the incorporation of soil flexibility is required for the realistic estimate of structural seismic response especially for single storey structures resting on very soft soil.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.6
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• pp.279-291
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• 2013

The seismic damage of non-structural components, such as communication facilities, causes direct economic losses as well as indirect losses which result from social chaos occurring with downtime of communication and financial management network systems. The current Korean seismic code, KBC2009, prescribes the design criteria and requirements of non-structural components based on their elastic response. However, it is difficult for KBC to reflect the dynamic characteristics of structures where non-structural components exist. In this study, both linear and nonlinear time history analyses of structures with various analysis parameters were carried out and floor acceleration spectra obtained from analyses were compared with both ground acceleration spectra used for input records of the analyses and the design floor acceleration spectrum proposed by National Radio Research Agency. Also, this study investigates to find out the influence of structural dynamic characteristics on the floor acceleration spectra. The analysis results show that the acceleration amplification is observed due to the resonance phenomenon and such amplification increases with the increase of building heights and with the decrease of structure's energy dissipation capacities.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.210-217
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• 2004

Developed is the new program that the reliability analysis can be performed more effectively considering the correlation of structural members about the cable stayed bridge. This program is formulated the stochastic finite element method suitable for the reliability analysis and the new safety evaluation method is proposed which is different from the existing one by the deterministic method or MCS response analysis. After conducting the initial equilibrium analysis of cable stayed bridges, the stochastic finite element is formulated through the perturbation method and the reliability analysis considering the correlation of stochastic variables is conducted. The results in various types of cable stayed bridge show that the probability of failure considering the correlation is larger than the non-correlation. The fan system is more stable than other systems at the structural response and the probability failure.

• Structural Engineering and Mechanics
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• v.42 no.2
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• pp.175-189
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• 2012

This paper presents an algorithm for structural reliability with the response surface method. For this aim, an approach with three stages is proposed named as improved response surface method. In the algorithm, firstly, a quadratic approximate function is formed and design point is determined with First Order Reliability Method. Secondly, a point close to the exact limit state function is searched using the design point. Lastly, vector projected method is used to generate the sample points and Second Order Reliability Method is performed to obtain reliability index and probability of failure. Five numerical examples are selected to illustrate the proposed algorithm. The limit state functions of three examples (cantilever beam, highly nonlinear limit state function and dynamic response of an oscillator) are defined explicitly and the others (frame and truss structures) are defined implicitly. ANSYS finite element program is utilized to obtain the response of the structures which are needed in the reliability analysis of implicit limit state functions. The results (reliability index, probability of failure and limit state function evaluations) obtained from the improved response surface are compared with those of Monte Carlo Simulation, First Order Reliability Method, Second Order Reliability Method and Classical Response Surface Method. According to the results, proposed algorithm gives better results for both reliability index and limit state function evaluations.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.545-552
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• 2001

Analysis of a structure for vertical vibration requires a lot of computational efforts because large number of degrees of freedom are generally involved in the dynamic response. Especially, when a structure is loaded with local vibration source, it may not be economical to model the whole structure to obtain the responses of specific members located near or far from the sources. In this study, substructure models have been used for analysis of local vibration An analysis of local vibration is performed for the case that the loaded point and the response point are located on the same floor. Other analysis is performed for the case that the loaded point and the response point are located on the different floor. In this case, if only the floors on which loaded and response points are located are modeled, response of substructure model is very different from that of full model. So, there should be a consideration that degrees of freedom of floors in addition to those of loaded and response floors are included to improve results of dynamic analysis. In this study, floors between loaded floor and response floor were modeled so that modeshapes which affect the response are presented well.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.35-43
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• 2012

In general, load carrying capacity, one of the load & resistance capacities in bridges, has more margins than the load carrying capacity evaluated with theoretical methods, unless there are severe damages, defects or material deterioration phenomena that can have a great impact on the behavior of bridges. However, errors have been already included in the current processes of loading tests and structural analysis for measuring load carrying capacity, thus devaluing the reliability of response adjustment factor. Therefore, this study found out the problems of existing electric resistance strain and displacement sensors in sensor suite to solve the problems with sensors and the errors in the appropriateness of structural analysis model, thereby leading to the changes into an optical fiber smart sensor with excellent performance. Besides, the study attempted to ensure the accuracy of response adjustment factor by selecting the optimal models through the interpretation of various structural analysis models.

• Wind and Structures
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• v.10 no.4
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• pp.383-398
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• 2007

The paper describes a study of the effects of structural coupling on the wind-induced response of twin tall buildings connected by a skybridge. Development of a dual high-frequency force balance used in wind tunnel investigation and background information on the methodology employed in analysis are presented. Comparisons of the wind-induced building response (rooftop acceleration) of structurally coupled and uncoupled twin buildings are provided and the influence of structural coupling is assessed. It is found that the adverse aerodynamic interference effects caused by close proximity of the buildings can be significantly reduced by the coupling. Neglecting of such interactions may lead to excessively conservative estimates of the wind-induced response of the buildings. The presented findings suggest that structural coupling should be included in wind-resistant design of twin tall buildings.

• Earthquakes and Structures
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• v.2 no.4
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• pp.337-356
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• 2011

In this paper, cable-stayed bridges with single pylon and two equal side spans, with variations in geometry and span ranging from 120 m to 240 m have been studied. 3D models of the bridges considered in this study have been analysed using ANSYS. As the first step towards a detailed seismic analysis, free vibration response of different geometries is studied for their mode shapes and frequencies. Typical pattern of free vibration responses in different frequencies with change in geometry is observed. Further, three different seismic loading histories are chosen with various characteristics to find the structural response of different geometries under seismic loading. Effect of variation in pylon shape, cable arrangement with variation in span is found to have typical characteristics with different structural response under seismic loading. From the study, it is observed that the structural response is very much dependent on the geometry of the cable-stayed bridge and the characteristics of the seismic loading as well. Further, structural responses obtained from the study would help the design engineers to take decisions on geometric shapes of the bridges to be constructed in seismic prone zones.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1773-1778
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• 2010

To evaluate the structural integrity of the main cooling-water pump of a nuclear power plant under different seismic conditions, the seismic analysis was performed in accordance with IEEE-STD-344 code. The finite element computer program, ANSYS, was used to perform both mode frequency analysis and response spectrum analysis for the pump assembly. The natural frequencies, the mode shapes, and the mode participation factors were obtained from the results of the mode frequency analysis. The stresses resulting from various loadings and their combinations were within the allowable limits specified in the above-mentioned IEEE code. The results of the seismic evaluation fully satisfied the structural acceptance criteria of the IEEE code. Thus, it was proved that the structural integrity of the pump assembly was satisfactory.