• Structural Engineering and Mechanics
• /
• v.75 no.1
• /
• pp.33-47
• /
• 2020

In this paper the dynamic behavior of an isolated building subjected to idealized near-fault pulses is investigated. The building is represented with a simple 2-DOF model. Both linear and non-linear behavior of the isolation system is considered. Using dimensional analysis, in conjunction with closed form mathematical idealized pulses, appropriate dimensionless parameters are defined and self-similar curves are plotted on dimensionless graphs, based on which various conclusions are reached. In the linear case, the role of viscous damping is examined in detail and the existence of an optimum value of damping along with its significant variation with the number of half-cycles is shown. In the nonlinear case, where the behavior of the building depends on the amplitude of the excitation, the benefits of dimensional analysis are evident since the influence of the dimensionless 𝚷-terms is easily examined. Special consideration is given to the normalized strength of the non-linear isolation system that appears to play a complex role which greatly affects the response of the 2-DOF. In the last part of the paper, a comparison of the responses to idealized pulses between a linear fixed-base SDOF and the respective isolated 2-DOF with both linear and non-linear damping is conducted and it is shown that, under certain values of the superstructure and isolation system characteristics, the use of an isolation system can amplify both the normalized acceleration and displacement of the superstructure.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.12 no.2
• /
• pp.35-42
• /
• 1992

The effectiveness of the support-isolation system for the equipment mounted on the primary structure is evaluated to reduce its responses under the earthquake load with considering the interaction between the primary structure and the internal equipment in this paper. A computer code (KBISAP) is developed to analyze the above system using the matrix condensation technique and constant average acceleration method. To evaluate the effectiveness of the support-isolation system, three systems are used in this study as follows: i) fixed-base structure with support-fixed equipment, ii) base-isolated structure with support-fixed equipment and iii) fixed-base structure with support-isolated equipment. The results of case study show that the acceleration of equipment with the support-isolation system is less than that of the support-fixed equipment in the base-isolated structure and significantly reduced the response compared with that of the support-fixed equipment in the fixed-base structure with the reduction factor of 8. The support-isolation system used in this study can reduce the response and also increase the safety margin of the important safety-related internal equipments.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.9 no.2
• /
• pp.205-217
• /
• 2007

The behavior characteristics of underground structures are reported as they are not affected by their dynamic characteristics such as surface structures, but by dynamic characteristics of soil and rock surrounding the underground structures. Therefore, dynamic behavior of surrounding soil and rock dominates the dynamic behavior of the underground structure. The purpose of this paper is to analyze the dynamic response (longitudinal deformation and ovaling deformation) of the underground structure under earthquake loading. The dynamic responses of the underground structures were evaluated with varying earthquake conditions, soil conditions, and structural conditions using conventional closed-form solution of seismic behavior of underground structure. In addition, shaking table tests were conducted to simulate the earthquake loading and the dynamic behavior of the model was analyzed.

• Journal of Korean Society of Steel Construction
• /
• v.9 no.4 s.33
• /
• pp.557-578
• /
• 1997

The objective of the study in this paper was to develop a beam-column element to model members with purely flexural yielding, as well as members with yielding under combined flexure and axial force during severe earthquake ground motins. The developed element can be considered as an one-component series hinge type model. It has the capability to model plastic axial deformation and changes in axial stiffness, and employs hardening rules to handle monotonic, cyclic or arbitrary loading. In general, when compared to experimental results and fiber model predictions, the element showed significantly better performance than the bilinear hinger model and could properly model the beam-column behavior of bare steel members in moment resisting frames. The developed element can more accurately predict local deformation demands and overall responses of structural systems under earthquake loadings than the bilinear hinge element.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.237-240
• /
• 2008

Today, some bridges or highways are becoming superannuated in Korea. Also, in this section, rehabilitation, replacement and expansion are necessary to increasing traffic volumes these days. Bridge reconstruction is major problem because it has relation to civil application, economical loss and loss of vehicles made a detour while this work. Many precast components and methods of construction are developed for this issue. Many research of various precast components and new materials are being performed owing to apply to prefabrication bridges. The present paper represents experimental studies on the performance of precast CFFT pier model. Also, stay-in-place RC pier and stay-in-place CFFT pier are made an experiment on due to comparing test results. Hysteretic responses of all columns are obtained through the test. Compared with the displacement ductility factors, conclusions of seismic performances can be made.

• Journal of the Korean Geotechnical Society
• /
• v.34 no.1
• /
• pp.25-35
• /
• 2018

Geocentrifuge tests are performed to investigate the structure-soil-structure interaction of shallow foundations that have various sizes. The soil specimen is prepared by using the air-pluviation, and the dynamic responses of the foundation are monitored with separation distances between the two foundations and the embedment. During the centrifugal test, the measured ground acceleration shows a tendency to increase with the increase of the input seismic amplitude, and maximum acceleration is measured at the surface due to the ground amplification. As the separation distance between the two foundations decreases, the ratio of the response spectral acceleration (RRS) increases and the period at the peak RRS decreases due to the structure-soil-structure interaction (SSSI). The RRS of the two foundations tends to decrease when the foundations are buried in the ground at the same separation distance.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.15 no.3
• /
• pp.27-35
• /
• 2011

Larbi (1995) and Jeong et al. (2005) analyzed the various boundary end conditions of buried pipelines using the mode superposition method as one of the dynamic analysis methods of buried pipelines. However, it is very complicated to derive calculation equations for the solutions to be obtained by this method, and even the derived calculation equations need separate computer programming for the numerical analysis in order to obtain the solutions. For this reason, this method is extremely difficult for engineers to apply in their field works. In consideration of the shortcoming of the mode superposition method, this study's purpose is to propose a 3D dynamic finite difference method, which is more easily applicable in the field. For this purpose, we tested the accuracy of the 3D dynamic analysis and compared the results with those of the mode superposition method and certified that the 3D dynamic analysis could be an alternative method to obtain the seismic responses of the pipelines.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.20 no.6
• /
• pp.401-412
• /
• 2016

On Tuesday, January 17, 1995, an earthquake of magnitude 7.2 struck the Port of Kobe. In effect, the port was practically destroyed. After a hazard investigation, researchers reached a consensus to adopt a performance-based design in port and harbor structures in Japan. A residual displacement of geotechnical structures after an earthquake is one of the most important engineering demands in performance-based earthquake-resistant design. Thus, it is essential to provide reliable responses of geotechnical structures after an earthquake through various techniques. Today, a nonlinear explicit response history analysis(NERHA) of geotechnical structures is the most efficient way to achieve this goal. However, verification of the effective stress analysis, including post liquefaction behavior, is difficult to perform at a laboratory scale. This study aims to rigorously verify the NERHA by using well-defined field measurements, existing numerical tools, and constitutive models. The man-made, Port Island, in Kobe provides intensive hazard investigation data, strong motion records of 1995 Kobe earthquake, and sufficient engineering parameters of the soil. Two dimensional numerical analysis was conducted on the caisson quay wall section at Port Island subjected to the 1995 Kobe earthquake. The analysis result matches very well with the hazard investigation data. The NERHA procedure presented in this paper can be used in further studies to explain and examine the effects of other factors on the seismic behavior of gravity quay walls in liquefiable soil areas.

• Earthquakes and Structures
• /
• v.12 no.4
• /
• pp.425-436
• /
• 2017

Vibration control using a tuned mass damper (TMD) is an effective technique that has been verified using analytical methods and experiments. It has been applied in mechanical, automotive, and structural applications. However, the damping of a TMD cannot be adjusted in real time. An excessive mass damper stroke may be introduced when the mass damper is subjected to a seismic excitation whose frequency content is within its operation range. The semi-active tuned mass damper (SATMD) has been proposed to solve this problem. The parameters of an SATMD can be adjusted in real time based on the measured structural responses and an appropriate control law. In this study, a stiffness-controllable TMD, called a leverage-type stiffness-controllable mass damper (LSCMD), is proposed and fabricated to verify its feasibility. The LSCMD contains a simple leverage mechanism and its stiffness can be altered by adjusting the pivot position. To determine the pivot position of the LSCMD in real time, a discrete-time direct output-feedback active control law that considers delay time is implemented. Moreover, an identification test for the transfer function of the pivot driving and control systems is proposed. The identification results demonstrate the target displacement can be achieved by the pivot displacement in 0-2 Hz range and the control delay time is about 0.1 s. A shaking-table test has been conducted to verify the theory and feasibility of the LSCMD. The comparisons of experimental and theoretical results of the LSCMD system show good consistency. It is shown that dynamic behavior of the LSCMD can be simulated correctly by the theoretical model and that the stiffness can be properly adjusted by the pivot position. Comparisons of experimental results of the LSCMD and passive TMD show the LSCMD with less demand on the mass damper stroke than that for the passive TMD.

• Steel and Composite Structures
• /
• v.35 no.2
• /
• pp.187-197
• /
• 2020

Ground motion records are commonly used for fragility curves (FCs) developing utilized in seismic loss estimating analysis for earthquake prone zones. These records could be 'real', say the recorded acceleration time series or 'simulated' records consistent with the regional seismicity and produced by use of alternative simulation methods. This study has focused on fragility curves developing for masonry buildings through computational 'simulated' ground motion records while evaluating the properness of these fragilities compared to the curves generated by the use of 'real' records. Assessing the dynamic responses of structures, nonlinear computational time history analyses through the equivalent single degree of freedom systems have been implemented on OpenSees platform. Accordingly, computational structural analyses of multi-story 3D frame structures with different stiffening members considering soil interaction have been carried out with finite element software according to (1992) Earthquake East-West component. The obtained results have been compared to each frame regarding soil interaction. Conclusion and recommendations with the discuss of obtaining findings are presented.