• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.422-429
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• 2003

A comparative study was performed for a suspension bridge to grasp the possible differences in seismic responses evaluated by several analytical methods. The items mainly investigated are the linear vs. nonlinear response the response spectrum method vs. the linear dynamic analysis method and the damping ratio and it's implementation into analysis procedures. According to the numerical example, it is found that the seismic responses are considerably affected by the damping-related parameters even though slight differences are shown depending on the response quantities md the exciting directions. On the other hand, it is also confirmed that the seismic responses are less affected by the analysis method-related parameters such as the response spectrum method vs. the linear dynamic analysis method, and the linear and nonlinear analysis method. The response spectrum method is expected to give conservative results for the examined bridge, provided that the design response spectrum in the Korean Highway Design Specification is modified according to the proper damping ratio.

• Journal of the Korea Institute of Military Science and Technology
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• v.4 no.1
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• pp.234-245
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• 2001

This paper considers the Maximum Pesponse Spectrum for the random vibration, sinusoidal vibration, linear sweep vibration. The random vibration quality levels and the sinusoidal vibration quality level are compared using MRS. And the severity between the vibration test specification and real environments using Maximum Response Spectrum are also compared using it.

• Structural Engineering and Mechanics
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• v.85 no.5
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• pp.655-664
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• 2023

Reinforced concrete (RC) shear wall structures are one of the most widely used structural systems to resist seismic loading all around the world. Although there have been several efforts to provide conceptually simple procedures to reasonably assess the seismic demands of structures over recent decades, it seems that lesser effort has been put on a number of structural forms such as RC shear wall structures. Therefore, this study aims to represent a simple linear response spectrum-based method which can acceptably predict the nonlinear displacements of a non-ductile RC shear wall structure subjected to an individual ground motion record. An effective period and an equivalent damping ratio are introduced as the dynamic characteristics of an equivalent linear SDOF system relevant to the main structure. By applying the fundamental mode participation factor of the original MDOF structure to the linear spectral response of the equivalent SDOF system, an acceptable estimation of the nonlinear displacement response is obtained. Subsequently, the accuracy of the proposed method is evaluated by comparison with another approximate method which is based on linear response spectrum. Results show that the proposed method has better estimations for maximum nonlinear responses and is more utilizable and applicable than the other one.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.1
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• pp.57-63
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• 2003

A comparative study was performed for a suspension bridge to grasp the possible differences in seismic responses evaluated by several analytical methods. The items mainly investigated are the linear vs. nonlinear response, the response spectrum method vs. the linear dynamic analysis method, and the damping ratio and it's implementation into analysis procedures. According to the numerical example, it is found that the seismic responses are considerably affected by the damping-related parameters even though slight differences are shown depending on the response quantities and the exciting directions. On the other hand, it is also confirmed that the seismic responses are less affected by the analysis method-related parameters such as the response spectrum method vs. the linear dynamic analysis method, and the linear and nonlinear analysis method. The response spectrum method is expected to give conservative results for the examined bridge, provided that the design response spectrum in the Korean Highway Design Specification is modified according to the proper damping ratio.

• Structural Engineering and Mechanics
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• v.32 no.1
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• pp.179-191
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• 2009

A stochastic response spectrum method is proposed for simple evaluation of the structural response of an actively controlled aseismic structure. The response spectrum is constructed assuming a linear structure with an active mass damper (AMD) system, and an earthquake wave model given by the product of a non-stationary envelope function and a stationary Gaussian random process with Kanai-Tajimi power spectral density. The control design is executed using a linear quadratic Gaussian control strategy for an enlarged state space system, and the response amplification factor is given by the combination of the obtained statistical response values and extreme value theory. The response spectrum thus produced can be used for simple dynamical analyses. The response factors obtained by this method for a multi-degree-of-freedom structure are shown to be comparable with those determined by numerical simulations, demonstrating the validity and utility of the proposed technique as a simple design tool. This method is expected to be useful for engineers in the initial design stage for structures with active aseismic control.

• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.1
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• pp.43-52
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• 2021

According to several seismic design standards, a ground motion time history should be selected similar to the design response spectrum, or a ground motion time history should be modified by matching procedure to the design response spectrum through the time-domain method. For the response spectrum matching procedure, appropriate seed ground motions need to be selected to maintain recorded earthquake accelerogram characteristics. However, there are no specific criteria for selecting the seed ground motions for applying this methodology. In this study, the characteristics of ground motion time histories between seed motions and spectral matched motions were compared. Intensity measures used in the design were compared, and their change by spectral matching procedure was quantified. In addition, the seed ground motion sets were determined according to the response spectrum shape, and these sets analyzed the response of nonlinear and equivalent linear single degrees of freedom systems to present the seed motion selection conditions for spectral matching. As a result, several considerations for applying the time domain spectral matching method were presented.

• Earthquakes and Structures
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• v.4 no.4
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• pp.341-363
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• 2013

Earthquake response calculation, parametric analysis and seismic parameter optimization of base-isolated structures are some critical issues for seismic design of base-isolated structures. To calculate the earthquake responses for such non-symmetric and non-classical damping linear systems and to implement the earthquake resistant design codes, a modified complex mode superposition design response spectrum method is put forward. Furthermore, to do parameter optimization for base-isolation structures, a graphical approach is proposed by analyzing the relationship between the base shear ratio of a seismic base-isolation floor to non-seismic base-isolation one and frequency ratio-damping ratio, as well as the relationship between the seismic base-isolation floor displacement and frequency ratio-damping ratio. In addition, the influences of mode number and site classification on the seismic base-isolation structure and corresponding optimum parameters are investigated. It is demonstrated that the modified complex mode superposition design response spectrum method is more precise and more convenient to engineering applications for utilizing the damping reduction factors and the design response spectrum, and the proposed graphical approach for parameter optimization of seismic base-isolation structures is compendious and feasible.

• Earthquakes and Structures
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• v.22 no.6
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• pp.585-595
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• 2022

Using the nonlinear static procedures has become very common in seismic codes to achieve the nonlinear response of the structure during an earthquake. The capacity spectrum method (CSM) adopted in ATC-40 is considered as one of the most known and useful procedures. For this procedure the seismic demand can be approximated from the maximum deformation of an equivalent linear elastic Single-Degree-of-Freedom system (SDOF) that has an equivalent damping ratio and period by using an iterative procedure. Data from the results of this procedure are plotted in acceleration- displacement response spectrum (ADRS) format. Different improvements have been made in order to have more accurate results compared to the Non Linear Time History Analysis (NL-THA). A new procedure is presented in this paper where the iteration process shall not be required. This will be done by estimation the ductility demand response spectrum (DDRS) and the corresponding effective damping of the bilinear system based on a new parameter of control, called normalized yield strength coefficient (η), while retaining the attraction of graphical implementation of the improved procedure of the FEMA-440. The proposed procedure accuracy should be verified with the NL-THA analysis results as a first implementation. The comparison shows that the new procedure provided a good estimation of the nonlinear response of the structure compared with those obtained when using the NL-THA analysis.

• Structural Engineering and Mechanics
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• v.21 no.3
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• pp.255-273
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• 2005

Based on the random vibration theory, a response spectrum method is developed for seismic response analysis of linear, multi-degree-of-freedom structures under multi-support excitations is developed. Various response quantities, including the mean and variance of the peak response, the response mean frequency, are obtained from proposed combination rules in terms of the mean response spectrum. This method makes it possible to apply the response spectrum to the seismic reliability analysis of structures subjected to multi-support excitations. Considering that the tedious numerical integration is required to compute the spectral parameters and correlation coefficients in above combination rules, this paper further offers simplified procedures for their computation, which enhance dramatically the computational efficiency of the suggested method. The proposed procedure is demonstrated for tow numerical examples: (1) two-span continuous beam; (2) two-tower cabled-stayed bridge by using Monte Carlo simulation (MC). For this purpose, this paper also presents an approach to simulation of ground motions, which can take into account both mean and variation properties of response spectrum. Computed results based on the response spectrum method are in good agreement with Monte Carlo simulation results. And compared with the MSRS method, a well-developed multi-support response spectrum method, the proposed method has an incomparable computational efficiency.

• Earthquakes and Structures
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• v.10 no.6
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• pp.1347-1367
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• 2016

The purpose of this work is to investigate the seismic behavior of St. Titus Church in Heraklion, Crete, Greece as well as the need of its seismic retrofitting. A numerical model of the Church is constructed using shell finite elements and it is then seismically examined using response spectrum and linear time-history analyses. Effects of soil-structure interaction have been also taken into account. The Church without retrofit is expected to exhibit extensive tensile failures and many compressive ones. Aiming to maintain the architectural character of the structure as well as to increase its seismic resistance, a retrofitting procedure involving injection of cement grout in conjunction with reinforced concrete jacketing to the internal side of the masonry walls is proposed. A numerical implementation of the proposed seismic retrofitting is performed and its effect is evaluated by response spectrum and linear time-history analyses. From the results of these analyses, it is shown that compressive failures are eliminated while only few tensile failures of local character take place.