• Earthquakes and Structures
• /
• v.13 no.4
• /
• pp.421-427
• /
• 2017

Seismic safety evaluation of weir structure is significant considering the catastrophic economical consequence of operational disruption. In recent years, the seismic probabilistic risk assessment (SPRA) has been issued as a key area of research for the hydraulic system to mitigate and manage the risk. The aim of this paper is to assess the seismic probabilistic risk of weir structures employing the seismic hazard and the structural fragility in Korea. At the first stage, probabilistic seismic hazard analysis (PSHA) approach is performed to extract the hazard curve at the weir site using the seismic and geological data. Thereafter, the seismic fragility that defines the probability of structural collapse is evaluated by using the incremental dynamic analysis (IDA) method in accordance with the four different design limit states as failure identification criteria. Consequently, by combining the seismic hazard and fragility results, the seismic risk curves are developed that contain helpful information for risk management of hydraulic structures. The tensile stress of the mass concrete is found to be more vulnerable than other design criteria. The hazard deaggregation illustrates that moderate size and far source earthquakes are the most likely scenario for the site. In addition, the annual loss curves for two different hazard source models corresponding to design limit states are extracted.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2005.03a
• /
• pp.453-460
• /
• 2005

In this study, the seismic fragility analysis of a base isolated condensate storage tank installed in the nuclear power plant. The condensate storage tank is safety related structure in a nuclear power plant. The failure of this tank affect significantly to the core damage frequency of the nuclear power plants. The seismic analysis of the liquid storage tank was performed by the simple calculation method and the dynamic time storage analysis method. The convective and impulsive fluid mass is modeled as added masses proposed by several researchers. To evaluate the effectiveness of the isolation system, the comparison of HCLPF and core damage frequencies in non-isolated and isolated cases are carried out. It can be found from the results that the seismic isolation system increases the seismic capacity of a condensate storage tank and decreases the core damage frequency significantly.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.20 no.7_spc
• /
• pp.517-526
• /
• 2016

In this paper, some popular intensity measures of earthquakes including magnitude, MMI, and PGA as well as their empirical relationships are briefly reviewed since they have been widely used without prudence by mass media, the public, and even the government when asking or expressing the seismic capacity of buildings. The basic concept of current seismic design is also presented in order to facilitate relevant discussions. It is emphasized that expressing the building seismic capacity simplistically in terms of seismological quantities or terminologies like magnitude and MMI is inherently irrational, may be misleading the stakeholders, and should be avoided. Alternative expressions, more rational and consistent with current seismic design philosophy and practice, are recommended.

• Structural Engineering and Mechanics
• /
• v.82 no.4
• /
• pp.417-434
• /
• 2022

In this work, a review of mechanical metamaterials and seismic protection systems that use them is carried out, focusing on passive protection systems. During the last years, a wide variety of classical systems of seismic protection have demonstrated to be an effective and practical way of reducing the seismic vulnerability of buildings, maintaining their health and structural integrity. However, with the emergence of metamaterials, which allow obtaining uncommon mechanical properties, new procedures and devices with high performance have been developed, reducing the seismic risk through novel approaches such as: seismic shields and the redirection of seismic waves; the use of stop band gaps and the construction of buried mass resonators; the design of pentamodal base isolators. These ideas are impacting traditional areas of structural engineering such as the design and building of highly efficient base isolation systems. In this work, recent advances in new seismic protection technologies and researches that integrate mechanical metamaterials are presented. A complete bibliometric analysis was carried out to identify and classify relevant authors and works related with passive seismic protection system based on mechanical metamaterial (pSPSmMMs). Finally, possible future scenarios for study and development of seismic isolators based on mechanical metamaterials are shown, identifying the relevant topics that have not yet been explored, as well as those with the greatest potential for future application.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.1
• /
• pp.235-242
• /
• 2011

The control performance in active structural control system can be drastically deteriorated when the modeling errors and the uncertainties existing in the disturbances are disregarded in the designing stage. It can even throw the control system into an unstable phase, resulting in out of control against the seismic excitations. The purpose of the study is to investigate the control effectiveness of a non-linear control system called sliding mode controller(SMC) in cooperation with a Tuned Mass Damper subjected to the three seismic excitations selected from the FFT analysis. Even though the transient performance such as settling time and overshoot were deteriorated, the robustness against the system stability was appeared from SMC when the structural masses and stiffness perturbed within the range of ${\pm}30%$. SMC is a feasible technique for active structural control in cooperation with TMD against seismic disturbances, exhibiting robustness in perturbation of system stiffness and mass as well as uncertainties of the disturbances.

• The Journal of the Acoustical Society of Korea
• /
• v.20 no.5
• /
• pp.14-20
• /
• 2001

The mass-spring system with four arms for the force-balance servo accelerometer was designed and fabricated. The response characteristics of a mass-spring system was calculated with the change of arms thickness and seismic mass by the finite element method (FEM). Furthermore, the response characteristics of accelerometer was measured using the change of interference pattern and response voltage value by Michelson interferometer. The response characteristics with changing length and thickness of arm was changed drastically, and changing seismic mass was minor effect for the response characteristics of mass-spring system. The measured resonant frequencies have good agreement with that of numerical analysis within 5％ range.

• Geomechanics and Engineering
• /
• v.30 no.5
• /
• pp.449-460
• /
• 2022

Safe underground construction in a rock mass requires adequate ground investigation and effective determination of rock conditions. The estimation of rock mass behavior is difficult, because rock masses are innately anisotropic and heterogeneous at different scales and are affected by various environmental factors. Quantitative rock mass classification systems, such as the Q-system and rock mass rating, are widely used for characterization and engineering design. The measurement of rock classification parameters is subjective and can vary among observers, resulting in questionable accuracy. Geophysical investigation methods, such as seismic surveys, have also been used for ground characterization. Torsional shear wave propagation characteristics in cylindrical rods are equal to that in an infinite media. A probabilistic quantitative relationship between the Q-value and shear wave velocity is thus investigated considering long-wavelength wave propagation in equivalent continuum jointed rock masses. Individual Q-system parameters are correlated with stress-dependent shear wave velocities in jointed rocks using experimental and numerical methods. The relationship between the Q-value and the shear wave velocity is normalized using a defined reference condition. This relationship is further improved using probabilistic analysis to remove unrealistic data and to suggest a range of Q-values for a given wave velocity. The proposed probabilistic Q-value estimation is then compared with field measurements and cross-hole seismic test data to verify its applicability.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2005.09a
• /
• pp.117-123
• /
• 2005

An in-hole seismic tests, which has been developed for measuring dynamic properties of soils and rock mass, is a bore hole seismic method that has cost effectiveness and practicality. The upgraded features include the motorized triggering system rather than the manual prototype version in the previous studies and a damper between source and receiver in the module. The performance of the probe has been verified through extensive cross-hole tests and in-hole tests at various sites. The dynamic stiffness of subsurface materials and rock mass have been evaluated and recently, the measurement of shear wave velocity was successfully adopted at horizontal holes of tunnel-face to install explosives. So the application of in-hole seismic test for various soil materials was certified.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.26 no.3
• /
• pp.105-116
• /
• 2022

Seismic demand on nonstructural components (NSCs) is highly dependent on the coupled behavior of a combined supporting structure-NSC system. Because of the inherent complexities of the problem, many of the affecting factors are inevitably neglected or simplified based on engineering judgments in current seismic design codes. However, a systematic analysis of the key affecting factors should establish reasonable seismic design provisions for NSCs. In this study, an idealized 2-DOF model simulating the coupled structure-NSC system was constructed to analyze the parameters that affect the response of NSCs comprehensively. The analyses were conducted to evaluate the effects of structure-NSC mass ratio, structure, and NSC nonlinearities on the peak component acceleration. Also, the appropriateness of component ductility factor (R_p) given by current codes was discussed based on the required ductility capacity of NSCs. It was observed that the responses of NSCs on the coupled system were significantly affected by the mass ratio, resulting in lower accelerations than the floor spectrum-based response, which neglected the interaction effects. Also, the component amplification factor (a_p) in current provisions tended to underestimate the dynamic amplification of NSCs with a mass ratio of less than 15%. The nonlinearity of NSCs decreased the component responses. In some cases, the code-specified R_p caused nonlinear deformation far beyond the ductility capacity of NSCs, and a practically unacceptable level of ductility was required for short-period NSCs to achieve the assigned amount of response reduction.

• Smart Structures and Systems
• /
• v.8 no.3
• /
• pp.239-252
• /
• 2011

In this study, the performances of a passive tuned mass damper (TMD) and a semi-active TMD (STMD) were evaluated in terms of seismic response control of elastic and inelastic structures under seismic loads. First, elastic displacement spectra were obtained for damped structures with a passive TMD and with a STMD proposed in this study. The displacement spectra confirmed that the STMD provided much better control performance than passive TMD and the STMD had less stroke requirement. Also, the robustness of the TMD was evaluated by off-tuning the frequency of the TMD to that of the structure. Finally, numerical analyses were conducted for an inelastic structure of hysteresis described by the Bouc-Wen model. The results indicated that the performance of the passive TMD whose design parameters were optimized for an elastic structure considerably deteriorated when the hysteretic portion of the structural responses increased, and that the STMD showed about 15-40% more response reduction than the TMD.