• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2003.03a
• /
• pp.238-246
• /
• 2003

By using simulated ground motions, which is sum of earthquake signals and noise, we measured the distortion of response spectra due to noise. We found that the distortion is more closely related to the signal-to-noise (S/N) ratio of root-mean-square (RMS) measurement than that of conventional peak measurement. Given a S/M ratio, the distortion of absolute acceleration response spectra is independent on the earthquake magnitude, while that of relative displacement response spectra has a strong dependence on the earthquake magnitude. This means that, when we calculate response spectra from time histories, we can efficiently predict the distortion of acceleration response spectra simply by measuring the RMS SJN ratios, or the distortion of displacement response spectra by combining the RMS S/N ratios and the earthquake magnitudes.

• Earthquakes and Structures
• /
• v.11 no.3
• /
• pp.421-443
• /
• 2016

When conducting seismic assessment of an asymmetric building, it is essential to carry out three-dimensional analysis considering all the possible directions of seismic input. For this purpose, the author proposed a simplified procedure is to predict the largest peak seismic response of an asymmetric building subjected to horizontal bidirectional ground motion acting in an arbitrary angle of incidence in previous study. This simplified procedure has been applied to torsionally stiff (TS) asymmetric buildings with regular elevation. However, the suitability of this procedure to estimate the peak response of an asymmetric building with vertical irregularity, such as an asymmetric building with setback, has not been assessed. In this article, the pushover-based simplified procedure is applied to estimate the peak response of asymmetric buildings with bidirectional setback. Nonlinear dynamic (time-history) analysis of two six-storey asymmetric buildings with bidirectional setback and designed according to strong-column weak beam concept is carried out considering various directions of seismic input, and the results compared with those estimated by the proposed method. The largest peak displacement estimated by the simplified method agrees well with the envelope of the dynamic analysis response. The suitability assessment of the simplified procedure to analysed building models is made as well based on pushover analysis results.

• Earthquakes and Structures
• /
• v.21 no.5
• /
• pp.551-562
• /
• 2021

In this study, the generalized intensity measure (IM) named I_Npg is analyzed. The recently proposed proxy of the spectral shape named N_pg is the base of this intensity measure, which is similar to the traditional N_p based on the spectral shape in terms of pseudo-acceleration; however, in this case the new generalized intensity measure can be defined through other types of spectral shapes such as those obtained with velocity, displacement, input energy, inelastic parameters and so on. It is shown that this IM is able to increase the efficiency in the prediction of nonlinear behavior of structures subjected to earthquake ground motions. For this work, the efficiency of two particular cases (based on acceleration and velocity) of the generalized I_Npg to predict the peak floor acceleration demands on steel frames under 30 earthquake ground motions with respect to the traditional spectral acceleration at first mode of vibration Sa(T₁) is compared. Additionally, a 3D reinforced concrete building and an irregular steel frame is used as a basis for comparison. It is concluded that the use of velocity and acceleration spectral shape increase the efficiency to predict peak floor accelerations in comparison with the traditional and most used around the world spectral acceleration at first mode of vibration.

• Earthquakes and Structures
• /
• v.9 no.3
• /
• pp.625-637
• /
• 2015

It is usual in design and assessment of structures to isolate the effects of vertical and horizontal excitations by ignoring their coupling effects. In this situation, total structural response is obtained by employing the well-known combination rules whereby independent assumed response components of earthquakes are combined. In fact, the effects of the simultaneity of the ground motion components are ignored. In this paper, the effect of vertical excitation on horizontal response of structures, the coupling of vertical and horizontal responses, has been evaluated. A computer program is prepared to perform nonlinear dynamic analysis based on the derived governing equations of coupled motions. In the case of simultaneous excitation the results show significant increases in spectral displacement in some periods of vibration in comparison to only horizontally excited systems. Moreover, whenever ratio of the vertical peak ground acceleration to horizontal one become larger, the significant increase in horizontal spectral displacements are observed.

• Smart Structures and Systems
• /
• v.26 no.2
• /
• pp.195-211
• /
• 2020

Among anti-seismic technologies, base isolation is a very effective means of mitigating damage to structural and nonstructural components, such as equipment. However, most seismic isolation systems are designed for mitigating only horizontal seismic responses because the realization of a vertical isolation system (VIS) is difficult. The difficulty is primarily due to conflicting isolation stiffness demands in the static and dynamic states for a VIS, which requires sufficient rigidity to support the self-weight of the isolated object in the static state, but sufficient flexibility to lengthen the isolation period and uncouple the ground motion in the dynamic state. To overcome this problem, a semi-active VIS, called the piezoelectric inertia-type vertical isolation system (PIVIS), is proposed in this study. PIVIS is composed of a piezoelectric friction damper (PFD) and a leverage mechanism with a counterweight. The counterweight provides an uplifting force in the static state and an extra inertial force in the dynamic state; therefore, the effective vertical stiffness of PIVIS is higher in the static state and lower in the dynamic state. The PFD provides a controllable friction force for PIVIS to further prevent its excessive displacement. For experimental verification, a shaking table test was conducted on a prototype PIVIS controlled by a simple controller. The experimental results well agree with the theoretical results. To further investigate the isolation performance of PIVIS, the seismic responses of PIVIS were simulated numerically by considering 14 vertical ground motions with different characteristics. The responses of PIVIS were compared with those of a traditional VIS and a passive system (PIVIS without control). The numerical results demonstrate that compared with the traditional and passive systems, PIVIS can effectively suppress isolation displacement in all kinds of earthquake with various peak ground accelerations and frequency content while maintaining its isolation efficiency. The proposed system is particularly effective for near-fault earthquakes with long-period components, for which it prevents resonant-like motion.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1992.10a
• /
• pp.140-154
• /
• 1992

The objective of the research stated here was aimed at providing the information needed to establish the Korean Seismic Design Code Recommendations and Guides for precast concrete (P.C) large panel apartment buildings. This was accomplished by investigation and analysis of the response of P.C large panel structures subjected to shaking table excitation simulating earthquake ground motion. one of the test specimens used was 1/3-scaled 3-story box P.C model provided by Sam-Hwan Camus Corporation. The 4m $\times$4m shaking table was used to simulate the earthquake ground motion. the employed input accelerogram was the one recorded as Taft N21E component and the peak ground acceleration(PGA) was scaled depending on the desired level of seismic severity and the time according to dynamic similitude rule. Based on results obtained from shaking table test of this P.C model, the following conclusions were drawn . (1) As far as test specimen is concerned, the seismic safety factors turns out to be 7~8. (2)P.C model has damping ratio of about8% which is twice larger than in-situ R.C. structure. And (3)this model has global displacement ductility ratio of 2~3 through the energy dissipation by opening and sliding of joints.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.20 no.6
• /
• pp.413-424
• /
• 2016

The vertical design spectrum for Korea, which is known to belong to an intra-plate region, is developed from the ground motion records of the earthquakes occurred in Korea and overseas intra-plate regions. From the statistical analysis of the vertical response spectra, a mean plus one standard deviation spectrum in lognormal distribution is obtained. Regression analysis is performed on this curve to determine the shape of spectrum including transition periods. The developed design spectrum is valid for the estimation both spectral acceleration and displacement. The ratio of vertical to horizontal response spectrum for each record is calculated. Statistical analysis of the ratios rendered the vertical to horizontal ratio (V/H ratio). Subsequently the ratio between the peak vertical ground acceleration to the horizontal one is obtained.

• Smart Structures and Systems
• /
• v.20 no.6
• /
• pp.641-656
• /
• 2017

The effects of vertical component of earthquakes on torsional amplification due to mass eccentricity in seismic responses of base-isolated structures subjected to near-field ground motions are studied in this paper. 3-, 6- and 9-story superstructures and aspect ratios of 1, 2 and 3 have been modeled as steel special moment frames mounted on Triple Concave Friction Pendulum (TCFP) bearings considering different period and damping ratios. Three-dimensional linear superstructures resting on nonlinear isolators are subjected to both 2 and 3 component near-field ground motions. Effects of mass eccentricity and vertical component of 25 near-field earthquakes on the seismic responses including maximum isolator displacement and base shear as well as peak superstructure acceleration are studied. The results indicate that the effect of vertical component on the responses of asymmetric structures, especially on the base shear is significant. Therefore, it can be claimed that in the absence of the vertical component, mass eccentricity has a little effect on the base shear increase. Additionally, the impact of this component on acceleration is remarkable so the roof acceleration of a nine-story structure has been increased 1.67 times, compared to the case that the structure is subjected to only horizontal components of earthquakes.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.5 no.2
• /
• pp.135-146
• /
• 2003

This paper presents the effect of ground vibration induced by vibrohammer and RCD on adjancent subway tunnel performance using FDM program. Firstly, the stability criteria for structures near vibration source were proposed according to existing data, then peak particle velocity around tunnel was estimated based on detailed information of vibrohammer and existing formula for dynamic loads through numerical analysis. The peak particle velocity induced by RCD bit rotation was also estimated using surveyed data and formula. Consequently, displacement and stress responses were obtained at crown, shoulder and spring line and compared with the criteria to check stability of tunnel.

• 한국체육학회지인문사회과학편
• /
• v.54 no.5
• /
• pp.829-840
• /
• 2015

The purpose of this study was to investigated into the kinematics and ground reaction force for gait on induced stereoacuity in normal subjects with normal sight. Eighteen subjects who passed the stereoacuity testing were participated in the experiment(age: 22.1±2.7 years, height: 176.8±4.4 cm, weight: 67.6±5.8 kg). The study method adopted 3D analysis with six cameras and ground reaction force with two force-plates. The results were as follows; In gait velocity, obstacle crossing gait was slower than flat gait. In angular displacement of hip joint, mostly obstacle crossing gait was more flexed than flat gait. In angular displacement of knee joint, obstacle crossing gait was more flexed than flat gait, and stereoacuity reduction gait in TO and FC2 were more flexed than normal vision gait. In angular displacement of ankle joint, obstacle crossing gait in FC2 was more flexed than flat gait. In trunk tilt, obstacle crossing gait in MSt, TO and MSw were more extended than flat gait. In GRF, there was no significant in Fx, obstacle crossing gait in right and left foot were bigger propulsion force than flat gait, obstacle crossing gait in right and left foot were bigger braking force than normal vision gait in Fy, and obstacle crossing gait in right and left foot were bigger than flat gait in peak F1 and peak F2 of Fz, and stereoacuity reduction gait in right foot was lower than normal vision gait in valley force of Fz.