• Nuclear Engineering and Technology
• /
• v.24 no.2
• /
• pp.111-120
• /
• 1992

This paper investigates the dynamic characteristics of spacer grid impact loads and the effects of variations in the amplitude and frequency of the core plate motions on the resultant impact loads. A model of the longest row (15 fuel assemblies) across the core is analyzed using the input motions generated from safe shutdown earthquake. Input excitations consist of time history motions applied to the core support plate, fuel alignment plate and core shroud. The responses are determined for a set of four parameter runs with respect to the amplitude and frequency changes. Spacer grid impact loads and normalized input values for all cases are presented. The results show that changing the natural frequency has negligible effect but changing the amplitude of the input motions has a significant effect on the grid impact loads Therefore, time history analysis is not necessary for a shifted case to get the core responses under the seismic excitation.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 1999.10a
• /
• pp.91-98
• /
• 1999

In this study a modified ground strain model is developed for an equivalent earthquake load and is applied to the seismic analysis of buried pipelines, The ground strain can be obtained using the ratio of a maximum ground velocity to a wave propagation velocity. To reflect soil conditions and seismic characteristics the wave propagation velocity is evaluated by a proposed dispersion curve based on wave energy distribution. In order to verify the procedures the observed earthquake data and the results of this study are compared. For the application of an equivalent earthquake load to the seismic analysis the buried pipelines are modeled using the beam theory. the results of the analyses are compared with those of a dynamic analysis code and those obtained from the response displacement method. Finally various parametric studies considering different soil conditions and seismic loads are examined.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1991.10a
• /
• pp.90-95
• /
• 1991

The Uniform Building Code (UBC) is the most widely used requirements for earthquake resistant design in the United States. In this paper, a mid-rise steel building is analyzed by applying 12 sets of actual strong-motion earthquake data that have been scaled to acne 2B levels. The simply extrapolated ground motion displacements are used for the dynamic loads. The results of dynamic analyses for a 10-story steel building are compared with the static and dynamic analysis requirements of UBC-88. It was found that computed lateral fortes using UBC-88 static procedure differed by about 60 percent depending on whether the natural period was computed using the UBC empirical method or the UBC recommended Rayleigh's method. The lateral fortes computed from the UBC response spectra were more than 10 times greater than those computed by UBC static procedures. The lateral forces obtained from both linear and nonlinear analyses using 1989 Loma Prieta ground mot ions compared very well with UBC response spectra results.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.6 no.5
• /
• pp.59-66
• /
• 2002

Long-rails in railways and high-speed railway are subjected to additional stresses resulted from the displacements inconsistence between upper structures, and this phenomenon is more remarkable in continuous bridges than in simple bridges. For the sake of safety, railways have to guarantee trains to stop safely without derailment even in the event of earthquake. The influences of acceleration, braking, and temperature were analyzed by static nonlinear method. But earthquake loads that require dynamic nonlinear analysis are not considered in these methods. Because linear relation between relative displacements of decks and rail stresses is not guaranteed at the nonlinear systems such as long rails on the bridges, it is required compute to rail stresses considering both braking and earthquake load by nonlinear dynamic analysis method. In this study, dynamic analysis method with material non-linearity for rails on continuous bridges according to the Taiwan High Speed Railway(THSR) Design Specification volume 9 was developed. And additional stresses and displacements of long rails for acceleration, braking, and earthquake loads were analyzed by this method.

• Earthquakes and Structures
• /
• v.26 no.2
• /
• pp.149-162
• /
• 2024

Aiming at the current research on the dynamic response analysis of the vehicle-bridge system under earthquake, which fails to comprehensively consider the impact of seismic wave incidence angles, terrain effects and soil-structure dynamic interaction on the bridge structure, this paper proposes a multi-point excitation input method that can consider the oblique incidence seismic P Waves based on the viscous-spring artificial boundary theory, and verifies the accuracy and feasibility of the input method. An overall numerical model of vehicle-bridge-soil foundation system in valley terrain during oblique incidence of seismic P-wave is established, and the effects of seismic wave incidence characteristics, terrain effects, soil-structure dynamic interactions, and vehicle speeds on the dynamic response of the bridge are analyzed. The research results indicate that with an increase in P wave incident angle, the vertical dynamic response of the bridge structure decreased while the horizontal dynamic response increased significantly. Traditional design methods which neglect multi-point excitation would lead to an unsafe structure. The dynamic response of the bridge structure significantly increases at the ridge while weakening at the valley. The dynamic response of bridge structures under earthquake action does not always increase with increasing train speed, but reaches a maximum value at a certain speed. Ignoring soil-structure dynamic interaction would reduce the vertical dynamic response of the bridge piers. The research results can provide a theoretical basis for the seismic design of vehicle-bridge systems in complex mountainous terrain under earthquake excitation.

• Journal of Korean Association for Spatial Structures
• /
• v.18 no.3
• /
• pp.133-140
• /
• 2018

Vertical earthquake motions can occur along with horizontal earthquakes, so that Structure should be designed to resist Seismic loads in all directions. Especially, due to the dynamic characteristics such as the vibration mode, when the vertical seismic load, the dynamic response of the Spatial structure is large. In this study, the seismic response of the lattice dome to horizontal and vertical seismic loads is analyzed, and a reasonable seismic load combination is analyzed by combining horizontal and vertical seismic response results. In the combination of the horizontal seismic load, the largest result is obtained when the direction of the main axis of the structure coincides with the direction of seismic load. In addition, the combination of vertical seismic load and horizontal seismic load was the largest compared with the combination of horizontal seismic load. Therefore, it is considered that the most reasonable and stable design will be achieved if the seismic load in vertical direction is considered.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2000.10a
• /
• pp.473-481
• /
• 2000

Civil structures are becoming more flexible and lightly damped. When subjected to dynamic loads such as wind, earthquake and wave, vibration may be easily induced and lasted for lond duration. To suppress the wind-induced and earthquake-induced vibration of high-rise buildings, study on the development of a tuned mass damper has been carried out. Based on optimal design on passive tuned mass damper which is considered for a building subject to random excitations, a biaxial tuned mass damper was designed and developed. It is confirmed that the vibration levels of the test structure are reduced using the developed tuned mass damper.

• Structural Engineering and Mechanics
• /
• v.11 no.6
• /
• pp.605-616
• /
• 2001

The purpose of this study is to investigate the effect of the shear wall location in rigid frames on the dynamic behavior of a roof structure due to vertical and horizontal earthquake motions. The study deals with a gabled long span beam supported by two story rigid frames with shear walls. The earthquake response analysis is carried out to study the responses of the roof: vibration mode, natural period, bending moment and horizontal shear force of the bearings. The study results in the following conclusions: First, a large horizontal stiffness difference between the side frames is caused by the shear wall location, which results in a large vertical vibration of the roof and a large shear force at the side bearings. Second, in this case, the seismic design method for ordinary buildings is not useful in determining the distribution of the static equivalent loads for the seismic design of this kind of long span structures.

• Earthquakes and Structures
• /
• v.2 no.3
• /
• pp.279-295
• /
• 2011

This paper develops a probabilistic methodology for the seismic reliability analysis of structures with random properties. The earthquake loading is assumed to be described in terms of response spectra. The proposed methodology takes advantage of the response spectra and thus does not require explicit dynamic analysis of the actual structure. Uncertainties in the structural properties (e.g. member cross-sections, modulus of elasticity, member strengths, mass and damping) as well as in the seismic load (due to uncertainty associated with the earthquake load specification) are considered. The structural reliability is estimated by determining the failure probability or the reliability index associated with a performance function that defines safe and unsafe domains. The structural failure is estimated using a performance function that evaluates whether the maximum displacement has been exceeded. Numerical illustrations of reliability analysis of elastic and elastic-plastic single-story frame structures are presented first. The extension of the proposed method to elastic multi-degree-of-freedom uncertain structures is also studied and a solved example is provided.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 1999.10a
• /
• pp.212-219
• /
• 1999

In this paper we investigated an applicability of earthquake regulations for seismic-isolated building structures which has been used currently and propose an efficient method for vertical distribution of seismic loads. The distribution of force is revised in UBC-94 as vertical distribution of force of UBC(Uniform Building Code)-91 is not sufficient safety but its distribution is inefficient expensive because of similar expression to fixed-based structures. In order to overcome this difficulties improved vertical distribution to fixed-based structures. In order to overcome this difficulties improved vertical distribution of seismic load is proposed using two degrees-of-freedom isolated structures and mode shape of fixed-based structures. Efficiency and accuracy of the proposed method are verified through analysis of an example structures with moment resisting frame and shear walls so this study approximate to dynamic analysis results in each case.