Proceedings of the Earthquake Engineering Society of Korea Conference (한국지진공학회:학술대회논문집)
Earthquake Engineering Society of Korea (EESK)
- 기타
Domain
- Earth Science(Earth/Atmosphere/Marine/Astronomy) > Geophysics
2001.04a
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The Ms 7.7 earthquake of Gujarat, India occured early in the morning of January 26, 2001. Subsequent of the earthquake, as a Seismologist at Korea Institute of Geoscience and Mineral Resources(KIGAM), I have been visited epicentral area here reporting the impressions and initial observations collected during the period of Feb. 07 to 13. The trace of surface faulting was not founded. However the mechanism of the earthquake suggests the indenting Indian plate to the Eurasian plate was the tectonic background of this earthquake. Large casualties compare with the magnitude and focal depth of the event, seems due to the poor construction of the typical ordinary Indian housing structure. The wall and roof of the house are very thick to avoid high temperature of the epicentral region.
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한반도 주요 지체구조구에 대한 최대지진을 지진 및 지질자료를 이용하여 여러 가지 방법으로 결정하였다. 한반도에서 발생한 가장 큰 지진은 MMI IX - X의 범위에 걸치며 이는 M= 7.0 - 7.7 에 해당한다. Gumbel의 극대치 제3분포를 이용하면 지체구조구별 최대지진은 M = 7.1 - 7.9의 범위에 놓이고, 응력방출 양상을 분석하면 M = 6.7 - 7.7 가 도출된다. 단층길이와 규모와의 상관관계에서 최대지진은 M = 7.4 - 7.6 에 놓인다. 한반도의 주요 지체구조구 사이에 최대지진의 현격한 차이를 나타내는 지진 및 지질학적 증거는 없다. 역사지진의 평가에서 강진들은 대략 1 계급( M=0.7) 과대 평가되는 경향이 있으므로, 한반도의 최대지진은 대략 M = 7.0으로 추정된다.
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In order to estimate attenuation characteristics, nonparametric model is used. Evaluation of this model requires suites of average spectral amplitude data as a function of distance without adopting any assumed parametric forms. Values of Quality factor, Q were estimated for individual frequencies by matrix inversion of S wave amplitude spectra for 21 records of 8 small and intermediate earthquakes (2.7
$(1/r)^{1/2}$. The best models for 1/Q values were found to be 0.000453+0.001851/f and 0.000451+0.009261/f, respectively. This results can be compared to the conventional functional form of Q= $af^{b}$ and be used to estimate source spectra and site response. -
It is essential to know exactly what the response of the seismograph is inclusive of characteristic of the seismic sensors before using it for detailed seismic study. This is because the recorded earthquake data can be more or less affected by the overall system and need to be corrected properly to the analysis`s best to obtain the right results. In this respect, two basic earthquake data processing techniques are introduced and applied, for validation purpose, to real data from KEPRI seismic monitoring system which were established for determining the site-specific characteristics of the earthquakes around the Nuclear Power Plants. One is conventional instrumental correction technique for velocity data and the other is for removing acausal ringing originate from using linear phase FIR filter. These techniques are all implemented in the time domain using digital filtering process and shows the desired results when applied to real earthquake data.
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Yangsan fault in the southeastern part of Korean peninsula has been locally reactivated along a prexisted fault during the late Pleistocene time. Geomorphological evidence of the reactivation is revealed at the northern segment(Yugye-ri, Tosung-ri areas) of the Yangsan fault. The reactivation is distinctively characterized by fault gouge and fracture zone with high frequency in the Yugye-ri area. Obique slip separation of the area is about three meters of the middle terrace. The cumulative vertical displacement is recognized after the formation of the middle terrace. Age of the reactivated faulting is constrained to during the formation of dissected valley deposits. Average vertical slip based on paleo-event is inferred to about 0.5-0.7 meter in this area.
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The estimation of recurrence interval for fault activity and earthquake is an important input parameter for seismic hazard assessment. In this study, the methods of recurrences interval estimation were reviewed and tentative calculation was performed for age dating data which have uncertainty. Age dating data come from previous studies of Ulsan fault system which is a well developed lineament in the southeastern part of korean Peninsula. Age dating for fault gouges, parent rocks, Quaternary sediments and veins were carried out by several researchers through various methods. Recurrence interval for fault activity was estimated on the basis of the age dating data of minor fault gouge and sediments during past 3Ma. The estimated recurrence interval was about 430-500 ka. Exact estimation of recurrence interval for fault activity need to compile more geological data and fault characteristics such as fault length, amount of displacement, slip rate and accurate fault movement age. In the future, the methods and results of fault recurrence interval estimation should be considered for establishing the criteria for domestic active fault definition.
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Several seismic traces of earthquakes observed from the digital new type seismograph instruments of KMA in 2000 were scanned. From these, good quality data which have high signal/noise ratio were selected and they were transformed into ascii data from binary data(min-seed format). The hypo71 program and P-S was applied in order to determine the location of epicenter, origin time and the magnitude. From these data, the 29 earthquakes, 358 seismic records consist of 587 directional components were calculated. Using these, ground acceleration data, acceleration, velocity, and displacemnet response spectrums of the structures were calculated and they could be represented in a picture by the form of tripartite response spectrum. In the result, response spectrums of the 587 directional components of the above seismic data records were obtained respectively.
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This paper is for a reasonable selection of design response spectra for the seismic design of specific types of soil-structure interaction systems, e.g., underground structure within flexible soil profiles of structures on the shallow soil layers on the stiff bed rock. the existing backup data used for determining the design response spectra of the Code have been investigated and evaluated. For this purpose, various types of free field analyses have been performed using one-dimensional wave propagation theory considering the nonlinear properties of the soil profile. As a result, a reasonable approach of determining input response spectra for specific soil profiles has been proposed to be compatible to the design response spectra of the Code.
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One major problem in the model testing is the boundary effect and size effect caused by the limit in the size of the container. To overcome this problem, various types of laminar boxes are gradually manufactured and used in the shaking table test, which ideally has zero stiffness to horizontal shear. In this study, a small-scale laminar box is manufactured, which is composed of 6 thin aluminum rectangular hollow plates, and its inside dimensions are 300 mm length by 200 mm width by 350 mm depth. Shaking table tests are performed both with the laminar box and the rigid box under the same conditions, where displacements and accelerations are measured at various points of the box and model ground. As result of analyzing the measured data, during the propagation of input seismic motion from the bottom to the ground surface, the relative displacement of the model ground and the amplification of acceleration is hardly amplified in the rigid box. Because of the effect of stress waves reflecting from the rigid wall, the acceleration is slightly decreased at the edge in the rigid box. The laminar box, manufactured in this study, has a problem in that the soil behavior at the edge of ground surface is affected by the inertia force of the top layer due to its excessive self-weight.
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The Spectral Analysis of surface Waves(SASW) Method has a great has a great potential for rapid determination of shear wave velocity profile of ground. However, it has an inherent limitation in the interpretation of test results due to the assumption that the ground is layered horizontally. The reason of the assumption is that difficulties exist in obtaining analytical solutions of wave equation when a soil system is composed of inclined soil layer. In this study, a finite-element method has been employed to assess the effects of dip angle and stiffness contrast of inclined soil layers and the testing direction on the dispersion curve. The propagation of wave front in the inclined soil layer was also investigated. The results indicated that the influence of dip angle on the dispersion curve is getting obvious as the dip angle increases and the propagation of wave front in the inclined layer also entirely different compared with the case of the horizontal layer.
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Long term earthquake observations at different tunnel sites within a variety of alluvial soil deposits have demonstrated that a circular tunnel is liable to deform in such a way that its two diagonal diameters crossing each other expand and contract alternately. Based on this knowledge, the soil-tunnel interaction and isolation effect for this particular vibration mode is investigated. Interaction effect is considered with the condition of fixed tangential strain between the tunnel and the soil. Isolation effect embodied by covering up the tunnel with isolation materials is discussed as a possible measure for mitigating seismic damage to it. When Poisson`s ratio of isolation material decreases or the shear modulus ratios of the soil to isolation material become large, the isolation effect becomes bigger.
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본 논문에서는 지반-구조물 상호작용계의 입력하중과 강성에 관련된 물성값들을 구조물에서 계측된 지진응답만을 사용하여 효과적으로 추정할 수 있는 새로운 방법을 제안하였는데, 제안된 방법은 비지계수 추정을 위한 목적함수가 입력하중에 독립적이기 때문에 구조물에서 계측된 지진응답만으로 미지계수의 추정이 가능하도록 되어있다. 본 연구에서 제안된 방법의 검증은 국제공동 연구의 일환으로 최근 대만의 화련에 건설된 대형지진시험 구조물에서 계측된 지진 응답을 사용하여 수행하였다. 추정된 입력하중과 지반과 구조물의 강성에 관련된 물성값들을 사용하여 계산된 지진응답의 계측치와 매우 잘 일치하여, 추정결과의 타당성을 검증할 수 있었다.
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In this study, a numerical analysis for soil-pile interaction systems in multi-layered half planes under a forced vibration is presented. The soil-pile interaction system is divided into two parts, so called near field and far field. The near field soil using finite elements and piles using beam elements are modeled. The far field soil media is implemented using boundary elements those can automatically satisfy the condition of wave radiation. These two fields are numerically coupled by imposing displacement compatibility condition at the interface between the near field and the far field. For the verification, the forced vibration test was simulated and the response under horizontal and vertical harmonic loads at the pile cap in the layered half plane was determined. The results are compared to the theoretical and experimental results of the literatures to verify the proposed soil-pile interaction analysis formulation.
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The development history of seismic design and analysis methods considering seismic force in soil-structure dynamic interaction are presented. Determination of seismic intensity in static analysis of both seismic and modifided seismic methods is discussed and preferable method in future seismic design is proposed.
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Comparison of results from two different methods of soil-structure dynamic interaction analysis is presented. Two methods include transfromed static and seismic response analyes. In seismic response analysis, the difference in result of total stress analysis relative to effective stress analysis is investigated.
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This paper presents sliding mode control(SMC) method using target variation rate of Lypunov Function. SMC keeps the response of structure in sliding surface where structure is stable. It can design both linear controller and bang-bang controller. Linear control of previous research, however, can not make most of the performance of controller, because it is designed to satisfy the condition that the variation rate of Lyapunov function is minus. Also, incase of bang-bang controller, unnecessary large control force is generated. Presented method can utilize the capacity of controller efficiently by prescribing the target variation rate of Lyapunov function. Numerical simulation results indicate that the presented control methods can reduce the peak response larger than linear control, and it has control performance equivalent to bang-bang control.
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비감쇠 혹은 비비례감쇠 시스템의 고유치를 구하기 위한 대부분의 방법들은 저차의 몇 개의 모드만을 사용하여 동적응답을 구하는 경우 누락된 고유치의 존재여부를 검사하기 위해 잘 알려진 Sturm 수열 성질(Sturm sequence property)을 이용한다. 반면 감쇠시스템 즉, 지반-구조물의 진동제어 시스템, 복합재료 구조물과 같은 경우에는 저차 몇 개의 모드만을 사용할 경우 누락 고유치를 검사할 수 있는 효율적인 기법이 아직 확립되지 않은 상태이다. 본 논문에서는 Gleyse의 정리를 이용하여 감쇠스템의 누락된 고유치를 검사하는 기법을 제안하고 이 방법의 효용성을 수치예제를 통하여 검증하였다.
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In this study, recently developed unscented Kalman filter (UKF) technique is studied for identification of nonlinear structural dynamic systems as an alternative to the extended Kalman filter (EKF). The EKF, which was originally developed as a state estimator for nonlinear systems, has been frequently employed for parameter identification by introducing the state vector augmented with the unknown parameters to be identified. However, the EKF has several drawbacks such as biased estimations and erroneous estimations especially for highly nonlinear dynamic systems due to its crude linearization scheme. To overcome the weak points of the EKF, the UKF was recently developed as a state estimator. Numerical simulation studies have been carried out on nonlinear SDOF system and nonlinear MDOF system. The results from a series of numerical simulations indicate that the UKF is superior to the EKF in the system identification of nonlinear dynamic systems especially highly nonlinear systems.
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In the present paper computational simulation of a concrete dam is performed to determine the effect of vertical ground motions on earthquake response of concrete dams. Cyclic and dynamic versions of the plastic-damage model proposed by Lee and Fenves are used to represent micro-crack development and crack opening/closing, which is important mechanism in nonlinear damage analysis of concrete structures subject to strong earthquake loading. The result shows that the vertical component of ground motion effects on final crack patterns and consequently, on displacement response.
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본 연구에서는 리브로 보강된 내진 철골 모멘트 접합부의 응력전달 메커니즘을 검토하였다. 리브보강 접합부의 응력전달 메커니즘은 고전 휨이론에 의한 예측과 전혀 다르다. 일반적으로 구조 기술자가 리브를 사용할 경우 단면이차모멘트의 증가에 따른 휨응력의 감소효과를 기대하는 것이 보통이다. 그러나 리브는 구조기술자들이 통상 가정하는 휨응력 전달요소라기 보다는 리브 구배 방향의 스트럿 요소로 기능하여 휨응력 외에도 전달응력을 전달한다. 리브를 스트럿 요소로 파악할 때 응력전달 메커니즘을 올바로 파악할 수 있으며 이를 기초로 합리적 설계법의 정립이 가능하다.
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The purpose of this paper is to suggest an analytical technique for time history analysis of R/C frame structure using high-strength concrete under seismic loading. Current researches in hysteretic model of structral elements using high-strength concrete are not enough. It is the cause of error that apply hysteretic model of element using normal-strength concrete to the inelastic analysis of high-strength concrete R/C frame structures. In this paper time history analysis using IDARC and DRAIN programs was performed for a 2-bay, 20-story R/C frame structures. Particularly nonlinear dynamic analysis was performed by IDARC program that was applied hysteretic model of structural element using high-strength concrete. centro earthquake 1940 NS waves was used in the analysis and its peak ground accelerations are changed to be 0.12g, 0.25g
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The purpose of this paper to describe an analytical model that is capable of reproducing the hysteretic behavior of beam-column joints under cyclic loading and to suggest the variable of hysteretic model for the inelastic analysis of R/C frame structures to do this quasi-static analysis using IDARC program was performed for the beam-column joints. The effort to obtain the result of analysis similar to those of experiment was made by determining the value for hysteretic parameters representing stiffness degradation, strength deterioration and pinching effect. The accuracy and reliability of the proposed analytical model was demonstrated by comparison of load-displacement relation, maximum strength, stiffness degradation and energy dissipation.
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In the evaluation of asymmetric buildings, torsional effects should be considered by three-dimensional analysis. However, this analysis is time-consuming and requires great efforts. The goal of this study is to give a comprehensible and simple procedure in the seismic evaluation by using two-dimensional analysis of asymmetric buildings so that practicing engineers can easily adapt it to their work.
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Unreinforced masonry is widely used as a structural material in residential constructions and known to have poor seismic performance in the out-of-plane rather than in-plane behavior. In countries of lower seismicity such as Korea, it is necessary to check the possibility of the mode of the out-of-plane failure. Though face loading is a major cause of the failure of masonary walls, Korean Seismic Code does not include provision for face-loaded unreinforced masonry walls. This paper briefly reviews the concept of analysis for unreinforced masonry walls subjected to face-load excitation proposed by Priestley, and its applicatility to Korean case.
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The purpose of this study is to evaluate the strength of piers subjected to earthquake ground motion. In particular, the piers of an unreinforced masonry wall under in-plane seismic loading are considered with emphasis. For this purpose, several pier strength equations in seismic rehailitation provisions such as UCBC, FEMA 178, FEMA 273, and FEMA 306 are compared. This strength equations in different provision are applied for calculating the strength of a pier in building. According to the results of this study, it is shown that the assessment procedure based on FEMA 178 overestimated pier strengths comparing to other provisions when all piers are in Rocking-controlled mode.
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The behavior of bridge column under multi-directional loading as well as uni-directional loading need to be studied because bridge columns will be subjected to the multi-directional cyclic loading during a strong earthquake. To evaluate the capacity of columns, uni-axial cyclic loading tests and bi-axial alternate cyclic loading tests were carried out. The number of cycles of alternate bi-axial loading were determined considering the ratio of natural frequencies in two orthogonal directions. From the test results, strength degradation and ductility reduction were observed in biaxial loading conditions. Their rates were found to be more rapid in the loading pattern that was determined considering the different natural frequencies.
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This study examines the fragility curves of a bridge by Capacity Spectrum Method. A sample of 10 nominally identical but statistically different bridge and 80 ground-motion time histories are considered to account for the uncertainties related to the structural capacity and ground motion, respectively. The comparison of fragility curves by Capacity Spectrum Method with those by time-history analysis indicates that the agreement is excellent for the state of at least minor damage, but not as good for the state of major damage where nonlinear effects clearly play a crucial role. Overall, however, the agreement is adequate even in the state of major damage considering the large number of typical assumptions under which the analyses of fragility characteristics are performed.
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Some as-built drawings in national roadway bridges in Korea were examined. There are many bridge piers, whose aspect ratios are in the vicinity of 2.5. These columns are expected to do shear-flexure behaviour and have large scale effect between full and reduced scale model. In the study, full and 1/2 scale model tests on the shear-flexure behaviour columns were carried out. The seismic performance of existing bridge piers without seismic details were examined by Quasi Static Test
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Recent destructive seismic events demonstrated the importance of mitigating human casualties and serious property damages in design and construction of structures. The Korean Bridge Design Specifications (1992) adopted seismic design requirements based on the AASHTO specification, and minor modification was made in 2000. The longitudinal steel connection of reinforced concrete bridge column is sometimes practically unavoidable. The longitudinal reinforcement details affect seisimc performance such as flexural failure and shear failure. This research aims to develop longitudinal steel connection details with confinement steel by experimental study for seismic performance of reinforced concrete bridge columns. Quasi-static test under three different axial load levels was conducted for 12 spiral column specimens. All the column specimens had the same aspect ratio of 3.5. The column specimens were transversely reinforced with spiral and with five different longitudinal steel connection. The final objective of this study is to suggest appropriate longitudinal reinforcement connection details for the limited ductility design concept and improve construction quality.
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An analysis procedure of 2-dimensional bridge dynamics has been developed by using force-deformation model, which simulates the pier motion under biaxial bending due to the bi-directional input seismic excitations. A three-dimensional mechanical model is utilized, which can consider the other major phenomena such as pounding, rotation of the superstructure, abutment stiffness degradation, and motions of the foundation motions. The bi-directional dynamic behaviors of the bridge are then examined by investigating the relative displacements of each oscillator to the ground. It is found that the nonlinearity of the pier due to biaxial bending affects the pier motions, but the global bridge behaviors are greatly governed by the pounding phenomena and stiffness degradation of the abutment-backfill system. Especially, the relative displacement of the abutment system (A2) with movable supports to the ground is increased about 30% due to the abutment stiffness degradation.
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This research aims at evaluating the seismic performance of the R/C bridge piers, which were seismically designed in accordance with the seismic provision of limited ductile behavior of Eurocode 8. Pseudo dynamic test for six(6) circular RC bridge piers has been carried out so at to investigate their seismic performance subjected to experted artificial earthquake motions. The objective of this experimental study is to investigate the hysteretic behavior of reinforced concrete bridge piers. Important test parameters are confinement steel ratio, input ground motion, etc. The seismic behavior of circular concrete piers under artificial ground motions has been evaluated through displacement ductility, energy analysis, capacity spectrum. It can be concluded that RC bridge piers designed in the seismic code of limited ductile behavior of Eurocode 8 have been determined to show good seismic performance even under expected artificial earthquakes in moderate seismicity region.
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To enhance seismic performance of a structure ATC-40 and FEMA-273 propose technical strategies such as increasing strength, altering stiffness, and reducing demand by employing base isolation and energy dissipation devices. Specifically the energy dissipation devices directly increase the ability of the structure to dampen earthquake response. However nonlinear dynamic time history analysis of a structure with energy dissipation devices is complicated and time consuming. In this study a simple and straightforward procedure is developed using effective damping ratio to obtain the required amount of viscoelastic dampers in order to meet given performance objectives. Parametric study has been performed for the period of the structure, yield strength, and the stiffness after the first yield. According to the analysis results, earthquake demand and required damping ratio were reduced by installing viscoelastic dampers. The results also show that with the addition of the supplemental damping evaluted by the proposed method the performance of the model structures are well restrained within the target point.
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Fluid viscous dampers have been used as energy dissipators or STU's (Shock Transmission Unit) in earthquake resistant designs for bridges. Viscous dampers have many advantages compared to other friction type or visco-elastic type of dampers. They do neither increase internal pier forces due to their out of phase response, nor produce reaction forces at the low velocities associated with thermal movements. Therefore, they anable the super structure to restore itself perfectly after a severe movement dut to seismic excitations. This paper investigates the response of bridges designed with viscous dampers in regard to damping coefficients, properties of dampers, and arrangements of dampers. For this purpose, time-history dynamic analyses have been performed using a very simple model relevant to a typical bridge example. Based on the results, it presents some design duidelines on how to determine a proper damping ratio and on how to arrange dampers. In usual cases, damping coefficients corresponding to about 0.2-0.3 of damping ratios seem to be very effective in bridge designs.
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Installing vibration control devices in the structure rises as a solution instead of increasing structural strength considering construction cost. Especially, viscoelastic dampers show excellent vibration control performance at low cost and are easy to install in existing structures compared with other control devices. Therefore, cost-effectiveness of structure with viscoelastic dampers needs to be evaluated. Previous cost-effectiveness evaluation method for the seismically isolated structure(Koh et al., 1999;2000)is applied on the building structure with viscoelastic dampers, which combines optimal design and cost-effectiveness evaluation for seismically isolated structures based on minimum life-cycle cost concept. Input ground motion is modeled in the form of spectral density function to take into account acceleration and site coefficients. Damping of the viscoelastic damper is considered by modal strain energy method. Stiffness of shear building and shear area of viscoelastic damper are adopted as design variables for optimization. For the estimation of failure probability, transfer function of the structure with viscoelastic damper for spectral analysis is derived from the equation of motion. Results reveal that cost-effectiveness of the structure with viscoelastic dampers is relatively high in how seismic region and stiff soil condition.
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In order to lessen cable vibration, new cable damper system with high damping rubber was developed using the basis of the LRB design scheme. The analysis model of cable damper system incorporate voigt-kelvin damper model into the nonlinear cable analysis model. To achieve maximum damping capacity both reducing damper stiffness and developing high damping rubber were performed. As a result of verification test, the high damping rubber damper show its effectiveness in improving cable damping capacity.
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Semi-active Control of Tall Building Subjected to Wind Loads Using Magneto-rheological Fluid Dampers고층 빌딩의 풍하중에 의한 진동을 제어하기 위하여 MR 유체감쇠기를 이용한 반능동 제어 시스템의 설계에 대하여 연구하였다. 제안된 설계기법의 효율성을 검증하기 위하여 3차 ASCE benchma가 구조물을 대상으로 수치 모의 해석을 수행하였다. 유전자 알고리즘을 사용하여 MR 감쇠기의 76층 빌딩내에서의 최적위치와 용량을 결정하였으며, clipped optimal control 제어기법을 사용하여 가속도 되먹임 구조를 갖는 MR 감쇠기의 제어 알고리즘을 구성하였다. 수치 모의 해석 결과로부터 MR 감쇠기는 ATMD와 유사한 제어 성능을 가지고 있으며 매우 작은 규모의 파워 시스템만으로 운영이 가능한 효율적이고 안정적인 시스템임을 확인할 수 있었다.
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The initial analysis frequencies of the isolated test structure for seismic excitation tests give quite higher values to the actual modal test results. This large difference was redulted from some uncertainties in analysis modeling of several connection regions between column and upper beam, cross bars of the isolated structure. A modified simple analysis model is developed representing the actual dynamic behaviors of the test model, and the seismic analysis responses of the simple model are compared with those of the seismic tests.
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The shear modulus of 3-bar lap rubber shear dynamic test specimen is investigated through incremented shear strain tests. The shear force-strain relation of rubber specimen is also calculated by ABAQUS using hyper-elastic material properties of high damping rubber. The analysis results are compatible with shear dynamic tests of 3-bar lap rubber specimen and 1/8 reduced-scale laminated rubber bearing
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Seismic performance of base isolated rigid-mass model were studied through shaking table tests. Friction pendulum systems (FPS), pure-friction systems with laminated rubber bearing (LRB) were selected for the comparison of performance. Performance of specially designed isolation systems were tested statically using actuator and dynamically using shaking table. Numerical methods were developed to simulate the nonlinear behavior of the frictional base isolation systems. Two models were considered. one is modified Bouc-Wen model considering breakaway coefficient of friction and the other is classical Coulomb model. The results of numerical methods are found to be in very good agreement with test results.
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A substructural model for a part of a long continuous bridge is identified using measured acceleration at limited locations within the part. Boundary spring constants and structural properties are idenfitied using a system identification method. The proposed method has been examined through simulation studies for static and dynamic responses and the results are discussed in the paper. The method is applied to an actual plate-girder gerber bridge with modal response obtained from a moving truck and construction blasting vibration
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Fatigue behavior of reinforced concrete(RC) and steel fiber reinforced concrete(SFRC) beams has been experimentally investigated. Fatigue behavior influenced by longitudinal reinforcement ratio, volume and type of steel fiber, strength of concrete and load ratio
$P_{u}/P_{o}$ . It can be observed from experimental results that addition of steel fiber to reinforced concrete beam reduces crack widths and increases stiffness, and thus enhances the behavior in serviceability limit states also for high cyclic fatigue loading. -
The seismic capacity of columns usually has been tested in uniaxial loading condition. The seismic performance used to be evaluated under the same assumption. Since the real earthquake motion is multi-directional, the effects of multi-directional excitation on the seismic capacity of structures need to be carefully examined. In this paper, a frequency dependent alternate biaxial cyclic loading test is proposed as an evaluation method of seismic capacity under multi-directional excitation. Four test specimens were made and tested to study the degradation of strength, stiffness and ductility under biaxial loading condition. A multi- directional excitation. The capacity is obtained using frequency dependent alternate biaxial cyclic loading test. The orthogonal effect is taken into account by increasing the demand.
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Shaking table tests were performed with full scale models of stone parapet on the ancient rampart. The objectives of these tests are to study the seismic behavior of the parapet and to obtain quantitative estimation of the intensities of historical earthquakes. Two test models were made based on the structure of the parapet remnant of a mountain fortress in Bukhan-San located in Seoul. Two types of infilling material are considered. The responses to models were tested subjected to three kinds of input motion.
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It can be seen through the previous earthquake damages that indirect damages such as those by fire are much greater rather than direct (firsthand) damage by earthquakes. Recently, gas is used very popularly all over the country but no measures have been taken against hazards (or dangers), for instance, such as fires caused by leaking gas pipes when earthquakes occur. Earthquake-Actuated Automatic Gas Shutoff Devices (Shutoff Device) are used to prevent such disaster in other countries. ChungJung Engineering. Co. is making a sample of a Shutoff Device for the first time in Korea. In this study, a derivation of mathermatical model and the important effects of various variables on the shutoff device are mentioned.