• Geomechanics and Engineering
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• 제23권1호
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• pp.1-13
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• 2020

To give a solution for seismic stability of tunnel faces subjected to earthquake ground shakings, the pseudo-dynamic approach is originally introduced to analyze tunnel face stability in this study. In the light of the upper-bound theorem of limit analysis, an advanced three-dimensional mechanism combined with pseudo-dynamic approach is proposed. Based on this mechanism, the required support pressure on tunnel face can be obtained by equaling external work rates to the internal energy dissipation and implementing an optimization searching procedure related to time. Both time and space feature of seismic waves are properly accounted for in the proposed mechanism. For this reason, the proposed mechanism can better represent the actual influence of seismic motion and has a remarkable advantage in evaluating the effects of vertical seismic acceleration, soil amplification factor, seismic wave period and initial phase difference on tunnel face stability. Furthermore, the pseudo-dynamic approach is compared with the pseudo-static approach. The difference between them is illustrated from a new but understandable perspective. The comparison demonstrates that the pseudo-static approach is a conservative method but still could provide precise enough results as the pseudo-dynamic approach if the value of seismic wavelengths is large or the height of soil structures is small.

• Geomechanics and Engineering
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• 제3권4호
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• pp.255-266
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• 2011

Knowledge of seismic earth pressure against rigid retaining wall is very important. Mononobe-Okabe method is commonly used, which considers pseudo-static approach. In this paper, the pseudo-dynamic method is used to compute the distribution of seismic earth pressure on a rigid cantilever retaining wall supporting dry cohesionless backfill. Planar rupture surface is considered in the analysis. Effect of various parameters like wall friction angle, soil friction angle, shear wave velocity, primary wave velocity, horizontal and vertical seismic accelerations on seismic earth pressure have been studied. Results are presented in terms of tabular and graphical non-dimensional form.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 춘계 학술발표회 논문집
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• pp.250-257
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• 2002

Pseudo dynamic test is an on-line computer control method to achieve the realism of shaking table test with the economy and versatility of the conventional quasi-static approach Pseudo dynamic tests of six full-size RC bridge piers have been carried out to investigate their seismic performance. For the purpose of precise evaluation, the experimental investigation was conducted to study the seismic performance of the real size specimen, which is constructed for highway bridge piers in Korean peninsula. Since it is believed that Korea belongs to the moderate seismicity region, five test specimens were designed in accordance with limited ductility design concept. Another one test specimen was nonseismically designed according to a conventional code. Important test parameters were transverse reinforcement and lap splicing. Lap splicing was frequently used in the plastic hinge region of many bridge columns. Furthermore, the seismic design code is not present about lap splice in Korean Roadway Bridge Design Code. The results show that specimens designed according to the limited ductility design concept exhibit higher seismic resistance. Specimens with longitudinal steel lap splice in the plastic hinge region appeared to significantly fail at low ductility level.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.885-890
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• 2002

Pseudo dynamic test is an on-line computer control method to achieve the realism of shaking table test with the economy and versatility of the conventional quasi-static approach. Pseudo dynamic tests of four full-size RC bridge piers have been carried out to investigate their seismic performance. For the purpose of precise evaluation, the experimental investigation was conducted to study the seismic performance of the real size specimen, which is constructed for highway bridge piers in Korean peninsula. Since it is believed that Korea belongs to the moderate seismicity region, three test specimens were designed in accordance with limited ductility design concept. Another one test specimen was nonseismically designed according to a conventional code. Important test parameters were transverse reinforcement and lap splicing. Lap splicing was frequently used in the plastic hinge region of many bridge columns. Furthermore, the seismic design code is not present about lap splice in Korean Roadway Bridge Design Code. The results show that specimens designed according to the limited ductility design concept exhibit higher seismic resistance. Specimens with longitudinal steel lap splice in the plastic hinge region appeared to significantly fail at low ductility level.

• 한국지진공학회논문집
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• 제11권1호
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• pp.21-27
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• 2007

본 연구에서는 교량의 내진보강을 위하여 기존 교량에 지진격리장치를 추가하는 접근법을 제안하였다. 기존 받침을 지진 격리받침으로 완전히 대체하는 접근법도 이미 제안되어 있지만 본 연구에서는 경제성과 안전성을 고려하여 기존 받침을 제거하지 않고 활용하도록 하였다. 이는 지진격리받침이 상부 수직하중을 분담하지 않고, 수평방향의 지진운동에 대한 주기 이동과 감쇠 역할만 한다. 이 접근법의 실험적 검증을 위해 실제 교량을 대상으로 납-적층고무받침(LRB)을 설계하고 실물크기로 기존 받침과 LRB를 제작하였다. 이 지진격리시스템의 가상 지진입력에 대한 응답은 유사동적실험으로 구하였다. 아울러 범용해석프로그램을 통한 지진응답해석과 비교하여 실험결과의 신뢰성을 확인하였다. 실험결과 제안된 지진격리시스템은 지진시 안정적인 거동을 보였다.

• 한국터널지하공간학회 논문집
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• 제7권3호
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• pp.249-257
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• 2005

지하구조물의 해석 방법은 크게 해석적 또는 유사정적 해석방법과 동적해석 방법의 두 종류로 나눌 수 있다. 유사정적 해석방법은 자유지반변형을 구조물에 정적인 하중으로 적용하여 구조물의 변위를 구하는 방법으로 선형탄성해석에 기초를 두고 있다. 그러나 치진 발생시 지반과 구조물 사이의 상호작용은 비선형 거동을 하여 이를 고려한 해석이 이루어져야 한다. 본 연구에서는 유사정적 해석방법에 반복계산과정에 의하여 지반의 비선형성을 고려할 수 있는 간편해석방법을 소개하고, 이를 수치해석을 통한 동해석을 수행하여 비교 검증하였다.

• 한국지진공학회논문집
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• 제22권1호
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• pp.15-22
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• 2018

Pseudo-static approach has been conventionally applied for the design of gravity type quay walls. In this method, seismic coefficient ($k_h$), expressed in terms of acceleration due to gravity, is used to convert the real dynamic behavior to an equivalent pseudo-static inertial force for seismic analysis and design. Therefore, the calculation of an appropriate $k_h$ considering frequency characteristics of input earthquake is critical for representing the real dynamic behavior. However, the definitions of $k_h$, which is used for simplified analysis in Korea, focuses only on convenience that is easy to use, and the frequency characteristics of input earthquake are not reflected in the $k_h$ definitions. This paper evaluates the influences of the frequency characteristics of input earthquake on $k_h$ by initially reviewing the $k_h$ definitions in the existing codes of Japan for port structures and then by performing a series of dynamic centrifuge tests on caisson gravity quay walls of different earthquake input motions (Ofunato, Hachinohe). A review of the existing codes and guidelines has shown that the $k_h$ values are differently estimated according to the frequency characteristics of input earthquake. On the other hand, based on the centrifuge tests, it was found that the permanent displacements of wall are more induced when long-period-dominant earthquake is applied.

• Structural Engineering and Mechanics
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• 제9권2호
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• pp.111-126
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• 2000

Truss type structures are attractive to a variety of engineering applications on earth as well as in space due to their high stiffness to mass ratios and ease of construction and fabrication. During the service life, an individual member of a truss structure may lose load carrying capacity due to many reasons, which may lead to collapse of the structure. An analytical and computational procedure has been developed to study the response of truss structures subject to member failure under static and dynamic loadings. Emphasis is given to the dynamic effects of member failure and the propagation of local damage to other parts of the structure. The methodology developed is based on nonlinear finite element analysis technique and considers elasto-plastic material nonlinearity, postbuckling of members, and large deformation geometric nonlinearity. The pseudo force approach is used to represent the member failure. Results obtained for a planar nine-bay indeterminate truss undergoing sequential member failure show that failure of one member can initiate failure of several members in the structure.

• 한국지진공학회논문집
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• 제21권2호
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• pp.77-85
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• 2017

Pseudo-static approach has been conventionally applied for the design of gravity quay walls. In this method, the decision to select an appropriate seismic coefficient ($k_h$) is an important one, since $k_h$ is a key variable for computing an equivalent pseudo-static inertia force. Nonetheless, there is no unified standard for defining $k_h$. Likewise, port structure designers in Korea have a difficulty in choosing an appropriate $k_h$ definition, as there are conflicts in how $k_h$ is defined between the existing seismic code of port structures and the proposed new one. In this research, various seismic design codes for port structures were analyzed to compare the definitions of the seismic coefficient. The results were used for the proposing a unified seismic coefficient definition. Further, two dynamic centrifuge tests were performed with different wall heights (5 m, 15 m) to clarify the reference point of peak acceleration used in determination of $k_h$ according to the wall height. Results from dynamic centrifuge experiments showed that correction factors for the peak ground acceleration considering both the wall height and allowable displacement are needed to calculate $k_h$.

• 한국구조물진단유지관리공학회 논문집
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• 제19권1호
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• pp.13-22
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• 2015

본 연구에서는 기존 강도증진형 내진보강법의 단점을 보완 개선할 수 있는 새로운 개념의 내진보강법인 RCSF (Reinforced Concrete Steel Frame) 외부접합형 내진보강공법을 제안하였다. RCSF 보강법은 거주자가 거주가 가능하면서 내진보강 공사를 실시할 수가 있으며, 접합부 시공성이 탁월하며, 특히 필요 내진보강량 산정이 간편한 전형적인 강도증진형으로 전단파괴가 지배적인 비내진상세를 가지는 국내 중 저층 철근콘크리트 건물에는 내력확보가 용이한 내진보강공법이다. 본 연구에서 제안한 RCSF 외부접합형 공법의 유용성을 검증 할 목적으로 기존 중 저층 철근콘크리트 학교건물의 골조를 대상으로 유사동적실험을 실시하여 검증함과 동시에 내진보강효과를 검토하였다. 그 결과, 국내에서 발생 가능한 최대 지진규모 (300gal)에서 비보강 골조는 붕괴를 하였지만, RCSF 외부접합형 내진보강법으로 보강한 골조는 경미한 지진피해가 예상되었으며, 대규모 지진 (400, 500gal)을 상정한 경우에도 소규모 이하의 지진피해가 예상되어 본 연구에서 개발한 RCSF 내진보강법의 유효성이 검증되었다고 사료된다.