연약지반에 건설된 단일형 현장타설말뚝 교량의 근단층지반운동에 대한 내진성능

선창호,안성민,김정한,김익현 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 논문집 Vol.23 No.7

For the structures near the seismogenic fault, the evaluation of seismic performance against near-fault ground motions is important as well as for design ground motions. In this study, characteristics of seismic behaviors and seismic performance of the pile-bent bridge constructed on the thick soft soil site with various weak soil layers were analyzed. The input ground motions were synthesized by the directivity pulse parameters for intra-plate regions. The ground motion acceleration histories of each layer were obtained by one-dimensional site response analysis. Each soil layer was modeled by equivalent linear springs, and multi-support excitations with different input ground motions at each soil spring were applied for nonlinear seismic analyses. The analysis result by the near-fault ground motions and ground motions matched to design spectra were compared. In case of the near fault ground motion input, the bridge behaved within the elastic range but the location of the maximum moment occurred was different from the result of design ground motion input. 근단층 지역에 위치한 교량은 근단층지반운동에 대한 내진안전성을 확보하는 것이 중요하다. 본 연구에서는 연약지반이 두껍고 다양한 지층으로 구성된 지역에 건설되는 단일형 현장타설말뚝 교량의 지진거동특성과 내진안전성을 분석하였다. 근단층지반운동을 생성하고 지반해석을 수행하여 각 지층에서의 지반가속도이력을 산정하였다. 이 가속도이력을 이용하여 각 지층의 지반을 등가스프링으로 모델화하고, 각 지층에서의 가속도시간이력을 입력지반운동으로 하는 다지점 가진 지진해석을 수행하였다. 근단층지반운동의 특성으로 인하여 교량은 탄성영역 내에서 거동하였지만 최대모멘트의 발생 위치 등이 설계지반운동을 고려할 때와는 상이한 특성을 보였다.

국가지진관측망 기반 지진동 데이터베이스 개발 연구

최세운,이준기,이상현,강태섭 한국지진공학회 2020 한국지진공학회논문집 Vol.24 No.6

In order to improve the ground-motion prediction equation, which is an important factor in seismic hazard assessment, it is essential to obtain good quality seismic data for a region. The Korean Peninsula has an environment in which it is difficult to obtain strong ground motion data. However, because digital seismic observation networks have become denser since the mid-2000s and moderate earthquake events such as the Odaesan earthquake (Jan. 20, 2007, ML 4.8), the 9.12 Gyeongju earthquake (Sep. 12, 2016, ML 5.8), and the Pohang earthquake (Nov. 15, 2017, ML 5.4) have occurred, some good empirical data on ground motion could have been accumulated. In this study, we tried to build a ground motion database that can be used for the development of the ground motion attenuation equation by collecting seismic data accumulated since the 2000s. The database was constructed in the form of a flat file with RotD50 peak ground acceleration, 5% damped pseudo-spectral acceleration, and meta information related to hypocenter, path, site, and data processing. The seismic data used were the velocity and accelerogram data for events over ML 3.0 observed between 2003 and 2019 by the Korean National Seismic Network administered by the Korea Meteorological Administration. The final flat file contains 10,795 ground motion data items for 141 events. Although this study focuses mainly on organizing earthquake ground-motion waveforms and their data processing, it is thought that the study will contribute to reducing uncertainty in evaluating seismic hazard in the Korean Peninsula if detailed information about epicenters and stations is supplemented in the future.

Distribution of Shear Coefficient of Multi-story Buildings Subjected to Near-fault Ground Motions

Wuchuan Pu,Ruijun Liang 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.9

In static seismic design, the strength demands of structural members are decided based on the expected shear force in a seismic event. A reasonable shear force distribution pattern leads to a reasonable configuration of structural parameters and thus makes the structure behave as expected in the design stage. In current seismic codes, the shear force distribution patterns are established based on the elastic response of structures subjected to ordinary far-fault ground motions. Because structural responses induced by pulselike near-fault ground motions are substantially different from the responses induced by far-fault ground motions, shear force patterns specified in current codes are not suitable for the structural design against near-fault ground motions, and a shear force distribution pattern considering the near-fault effect should be established. This study aims to investigate the characteristics of shear coefficients resulting from near-fault ground motions and to provide a new shear force distribution pattern specifically for seismic design against near-fault ground motions. To achieve this goal, dynamic time history analyses are performed on elastic shear models based on 50 near-fault ground motions, and the shear force distributions are analyzed statistically. Findings from the study reveal that the higher modes contribute substantially to the shear coefficient, and the contribution is affected by the pulse period of the ground motion and the structural damping. The shear coefficients for floor levels 2/3 of the way up the height of the structure are significantly larger than code-specified values, if the structure has a limited damping ratio. Based on the numerical results, an empirical formula of the shear coefficient pattern is proposed. In this formula, the effects of damping ratio and period ratio are taken into account, and it can be used to derive shear coefficients more suitable for structures subjected to pulse-like near-fault ground motions.

Study on Seismic Source Parameters for Earthquakes Occurring from 2001 to 2016 in the Korean Peninsula

( Hae-geun Jeong ),( Hyun-me Lee ),( Heon-woo Kwon ),( Seung-hee Do ),( Kyung-soo Lee ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Seismic source parameters such as static stress drop, coner frequency, and seismic moment of earthquakes have been widely used to describe important charateristics of seismic source, seismicity, and stochastic simulation in the region. This study measured the seismic source parameters of 760 earthquakes occurred from January 2001 to December 2016 in the Korean Peninsula. The method on S-wave spectrum analysis of Jo and Baag(2001) which was based on method of Snoke(1987) and Andrews(1986) was used to caculate the seismic source parameters. The regions near Pyongyang and South-Western part of East-Sea shown low stress drop in the relative difference distribution of stress drop. It is also shown that the region of low stress drop are very similar to region of high seismicity. We suggest the regional variations in the stress drop. By applying the seismic source parameters of mainshock of the Gyeongju earthquake on 12 September 2016, stochastic ground motion simulation were performed. The comparison between observed response spectrum and simulated response spectrum shown the significant effect of sesimic source parameters in stochastic ground motion simulation. Therefore the seismic source parameters measured from this study could be used to seismic safety assessment field such as development of ground motion predict equation and finite fault modeling.

An Improved Ground Motion Model Based on Spatial Random Field

( Ye Yizhou ),( Huang Yu ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Reasonable ground motion input is very important for studies of earthquake hazard analysis and the seismic design of engineering structures in high seismic intensity area. Due to the fact that the ground motion characteristics are strongly affected by the slip distribution of earthquake rupture, the source parameters and the relationship between the moment magnitude are established from the physical mechanism of earthquake source. We establish the multi-parameter correlation random field source model about the source, the rise time, and the scaling of rupture to show the random characteristics of seismic source better. Choose three commonly used correlation functions such as the Gaussian, exponential and Von Karman correlation function, to control the spatial statistics of slip distribution and define the covariance matrix. On this basis, this study attempts to use the Green’s function to describe the uncertainties in earthquake source and the path of seismic waves. Then, it establishes a bedrock seismic motion model which can reflect the effect of earthquake source uncertainties, and take Cascadia subduction zone as an example, uses the improved spatial random field model to simulate the stochastic slip of faults and obtain the random earthquake ground motion. The final results show the model is a good method for strong ground motion simulation.

Seismic Fragility Analysis of a CANDU Type NPP Containment Building for Near-fault Ground Motions

In-Kil Choi,Young-Sun Choun,Seong-Moon Ahn,Jeong-Moon Seo 대한토목학회 2006 KSCE journal of civil engineering Vol.10 No.2

In this study, the seismic fragility of a CANDU (CANada Deuterium Uranium) containment building is estimated by performing the nonlinear seismic analysis for the near-fault earthquakes. The lumped mass model of the containment building was used for a nonlinear dynamic time history analysis. The tri-linear skeleton curve was used for the nonlinear behavior of the prestressed concrete containment building. In order to estimate the inelastic nonlinear response of the containment, the maximum point oriented model was used for the hysteretic rule of the shear deformation, For the nonlinear seismic analyses, 30 set of real near-fault earthquake records were used as the input motion. The seismic responses and seismic fragility of the containment for the near-fault ground motions are compared with the responses and fragility for the design ground motion generally used in Korea.

응답 스펙트럼의 평균과 분산, 상관관계를 모두 고려한 지반운동 선정 방법 – II 지진 응답

한상환,하성진 한국지진공학회 2016 한국지진공학회논문집 Vol.20 No.1

This study is the sequel of a companion paper (I. Algorithm) for assessment of the seismic performance evaluation of structure using ground motions selected by the proposed algorithm. To evaluate the effect of the correlation structures of selected ground motions on the seismic responses of a structure, three sets of ground motions are selected with and without consideration of the correlation structure. Nonlinear response history analyses of a 20-story reinforced concrete frame are conducted using the three sets of ground motions. This study shows that the seismic responses of the frames vary according to ground motion selection and correlation structures.

장주기 지진동을 고려한 면진층과 상부구조물의 동적응답특성

김주찬,오상훈 대한건축학회 2023 대한건축학회논문집 Vol.39 No.6

Seismically isolated structures employ a structural system that incorporates an isolation layer within the building, effectively isolating thesuperstructure from ground motions. Typically positioned at the building’s foundation, this isolation layer lengthens the structure's naturalperiod, thereby reducing the acceleration response of the superstructure. However, concerns arise in seismically isolated structures regardingthe potential for significant displacement of the isolation layer due to long-period ground motion. Furthermore, the amplification of thelong-period component of ground motion by the isolation layer poses a risk of earthquake damage to both the superstructure and thenon-structural components attached to it. Consequently, this study aims to examine the dynamic response characteristics of both the isolationlayer and the superstructure through nonlinear time history analysis, taking into account the influence of long-period ground motions. Theanalysis model utilized in this study follows the energy-based seismic design method proposed by Akiyama (1985). The key variablesconsidered in the analysis include the natural period of the isolation layer, the natural period of the superstructure, and the horizontal yieldstrength of the superstructure. 면진구조는 건축물에 면진층을 설치하여, 지진으로부터 면진층의 상부구조물을 격리시키는 형태의 구조시스템이다. 일반적으로 면진층은 건축물의 기초부에 배치되며, 면진구조 건축물의 장주기화로 인해 상부구조물에 응답되는 가속도가 감소한다. 하지만 면진구조는 건축물의 장주기화로 인하여 장주기 지진동에 의해 면진층의 변위가 크게 발생할 우려가 있다. 또한 면진층에 의해 증폭된 지진동의 장주기 성분이 상부구조물과 상부구조물에 부착된 비구조요소에 지진피해를 발생시킬 수 있다. 따라서 본 연구에서는 장주기 지진동을 고려한 비선형 시간이력해석을 통해 면진층과 상부구조물의 동적응답특성을 검토하고자 한다. 해석모델의 설계는 Akiyama(1985)가 제안한 에너지 기반 내진설계 방법을 바탕으로 수행하고자 한다. 해석변수는 면진층의 고유주기, 상부구조물의 고유주기, 상부구조물의 수평 항복내력이다.

Seismic response and failure analyses of pile-supported transmission towers on layered ground

Haiyang Pan,Chao Li,Li Tian 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.2

Transmission towers have come to represent one of the most important infrastructures in today’s society, which may suffer severe earthquakes during their service lives. However, in the conventional seismic analyses of transmission towers, the towers are normally assumed to be fixed on the ground without considering the effect of soil-structure interaction (SSI) on the pile-supported transmission tower. This assumption may lead to inaccurate seismic performance estimations of transmission towers. In the present study, the seismic response and failure analyses of pile-supported transmission towers considering SSI are comprehensively performed based on the finite element method. Specifically, two detailed finite element (FE) models of the employed pile-supported transmission tower with and without consideration of SSI effects are established in ABAQUS analysis platform, in which SSI is simulated by the classical p-y approach. A simulation method is developed to stochastically synthesize the earthquake ground motions at different soil depths (i.e. depth-varying ground motions, DVGMs). The impacts of SSI on the dynamic characteristic, seismic response and failure modes are investigated and discussed by using the generated FE models and ground motions. Numerical results show that the vibration mode shapes of the pile-supported transmission towers with and without SSI are basically same; however, SSI can significantly affect the dynamic characteristic by altering the vibration frequencies of different modes. Neglecting the SSI and the variability of earthquake motions at different depths may cause an underestimate and overestimate on the seismic responses, respectively. Moreover, the seismic failure mode of pile-supported transmission towers is also significantly impacted by the SSI and DVGMs.

원거리와 근거리 지진파의 특성을 고려한 항만 컨테이너 크레인의 지진취약도 분석

박주현,민지영,이종한 한국지진공학회 2023 한국지진공학회논문집 Vol.27 No.2

The recent increase in earthquake activities has highlighted the importance of seismic performance evaluation for civil infrastructures. In particular, the container crane essential to maintaining the national logistics system with port operation requires an exact evaluation of its seismic response. Thus, this study aims to assess the seismic vulnerability of container cranes considering their seismic characteristics. The seismic response of the container crane should account for the structural members’ yielding and buckling, as well as the crane wheel’s uplifting derailment in operation. The crane’s yielding and buckling limit states were defined using the stress of crane members based on the load and displacement curve obtained from nonlinear static analysis. The derailment limit state was based on the height of the rail, and nonlinear dynamic analysis was performed to obtain the seismic fragility curves considering defined limit states and seismic characteristics. The yield and derailment probabilities of the crane in the near-fault ground motion were approximately 1.5 to 4.7 and 2.8 to 6.8 times higher, respectively, than those in the far-fault ground motion.