• Title/Summary/Keyword: Seismic Response Coefficient

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Typical Seismic Intensity Calculation for Each Region Using Site Response Analysis (부지응답해석을 이용한 지역별 대표 진도 산출 연구)

  • Ahn, Jae-Kwang;Son, Su-Won
    • Journal of the Korean GEO-environmental Society
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    • v.21 no.1
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    • pp.5-12
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    • 2020
  • Vibration propagated from seismic sources has damping according to distance and amplification and reduction characteristic in different regions according to topography and geological structure. The vibration propagated from the seismic source to the bedrock is largely affected by the damping according to the separation distance, which can be simply estimated through the damping equation. However, it is important to grasp geological information by location because vibration estimation transmitted to the surface are affected by the natural period of the soil located above the bedrock. Geotechnical investigation data are needed to estimate the seismic intensity based on geological information. If there is no Vs profile, the standard penetration tests are mainly used to determine the soil parameters. The Integrated DB Center of National Geotechnical Information manages the geotechnical survey data performed on the domestic ground, and there is the standard penetration test information of 400,000 holes. In this study, the possibility of quantitation the amplification coefficient for each region was examined to calculated the physical interactive seismic intensity based on geotechnical information. At this time, the shear wave column diagram was generated from the SPT-N value and ground response analysis was performed in the target area. The site coefficients for each zone and the seismic intensity distribution for the seismic motion present a significant difference according to the analysis method and the regional setting.

Regional Seismic Risk Assessment for Structural Damage to Buildings in Korea (국내 건축물 지진피해 위험도의 지역단위 평가)

  • Ahn, Sook-Jin;Park, Ji-Hun;Kim, Hye-Won
    • Journal of the Earthquake Engineering Society of Korea
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    • v.27 no.6
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    • pp.265-273
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    • 2023
  • This study proposes a methodology for the regional seismic risk assessment of structural damage to buildings in Korea based on evaluating individual buildings, considering inconsistency between the administrative district border and grid lines to define seismic hazard. The accuracy of seismic hazards was enhanced by subdividing the current 2km-sized grids into ones with a smaller size. Considering the enhancement of the Korean seismic design code in 2005, existing seismic fragility functions for seismically designed buildings are revised by modifying the capacity spectrum according to the changes in seismic design load. A seismic risk index in building damage is defined using the total damaged floor area considering building size differences. The proposed seismic risk index was calculated for buildings in 29 administrative districts in 'A' city in Korea to validate the proposed assessment algorithm and risk index. In the validation procedure, sensitivity analysis was performed on the grid size, quantitative building damage measure, and seismic fragility function update.

Seismic structural demands and inelastic deformation ratios: Sensitivity analysis and simplified models

  • Chikh, Benazouz;Laouami, Nacer;Mebarki, Ahmed;Leblouba, Moussa;Mehani, Youcef;Kibboua, Abderrahmane;Hadid, Mohamed;Benouar, Djillali
    • Earthquakes and Structures
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    • v.13 no.1
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    • pp.59-66
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    • 2017
  • Modern seismic codes rely on performance-based seismic design methodology which requires that the structures withstand inelastic deformation. Many studies have focused on the inelastic deformation ratio evaluation (ratio between the inelastic and elastic maximum lateral displacement demands) for various inelastic spectra. This paper investigates the inelastic response spectra through the ductility demand ${\mu}$, the yield strength reduction factor $R_y$, and the inelastic deformation ratio. They depend on the vibration period T, the post-to-preyield stiffness ratio ${\alpha}$, the peak ground acceleration (PGA), and the normalized yield strength coefficient ${\eta}$ (ratio of yield strength coefficient divided by the PGA). A new inelastic deformation ratio $C_{\eta}$ is defined; it is related to the capacity curve (pushover curve) through the coefficient (${\eta}$) and the ratio (${\alpha}$) that are used as control parameters. A set of 140 real ground motions is selected. The structures are bilinear inelastic single degree of freedom systems (SDOF). The sensitivity of the resulting inelastic deformation ratio mean values is discussed for different levels of normalized yield strength coefficient. The influence of vibration period T, post-to-preyield stiffness ratio ${\alpha}$, normalized yield strength coefficient ${\eta}$, earthquake magnitude, ruptures distance (i.e., to fault rupture) and site conditions is also investigated. A regression analysis leads to simplified expressions of this inelastic deformation ratio. These simplified equations estimate the inelastic deformation ratio for structures, which is a key parameter for design or evaluation. The results show that, for a given level of normalized yield strength coefficient, these inelastic displacement ratios become non sensitive to none of the rupture distance, the earthquake magnitude or the site class. Furthermore, they show that the post-to-preyield stiffness has a negligible effect on the inelastic deformation ratio if the normalized yield strength coefficient is greater than unity.

Development of the Optimal Performance Based Seismic Design Method for 2D Steel Moment Resisting Frames (2차원 철골 구조물의 최적 성능기반 내진설계법 개발)

  • Kwon Bong-Keun;Lee Hyun-Kook;Kwon Yun-Man;Park Hyo-Seon
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2005.04a
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    • pp.636-643
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    • 2005
  • Recently, performance based seismic design (PBSD) methods have been suggested in numerous forms and widely studied as a new concept of seismic design. The PBDSs are far from being practical method due to complexity of algorithms resided in the design philosophy. In this paper, optimal seismic design method based on displacement coefficient method (DCM) described in FEMA 273 is developed. As an optimizer simple genetic algorithms are used for implementations. In the optimization problem formulated in this Paper, strength design criteria stiffness design criteria, and nonlinear response criteria specified in DCM are included in design constraints. The optimal performance based design(OPBD) method is applied to seismic design of a 3-story two-dimensional steel frame structures.

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Simplified procedure for seismic demands assessment of structures

  • Chikh, Benazouz;Mehani, Youcef;Leblouba, Moussa
    • Structural Engineering and Mechanics
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    • v.59 no.3
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    • pp.455-473
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    • 2016
  • Methods for the seismic demands evaluation of structures require iterative procedures. Many studies dealt with the development of different inelastic spectra with the aim to simplify the evaluation of inelastic deformations and performance of structures. Recently, the concept of inelastic spectra has been adopted in the global scheme of the Performance-Based Seismic Design (PBSD) through Capacity-Spectrum Method (CSM). For instance, the Modal Pushover Analysis (MPA) has been proved to provide accurate results for inelastic buildings to a similar degree of accuracy than the Response Spectrum Analysis (RSA) in estimating peak response for elastic buildings. In this paper, a simplified nonlinear procedure for evaluation of the seismic demand of structures is proposed with its applicability to multi-degree-of-freedom (MDOF) systems. The basic concept is to write the equation of motion of (MDOF) system into series of normal modes based on an inelastic modal decomposition in terms of ductility factor. The accuracy of the proposed procedure is verified against the Nonlinear Time History Analysis (NL-THA) results and Uncoupled Modal Response History Analysis (UMRHA) of a 9-story steel building subjected to El-Centro 1940 (N/S) as a first application. The comparison shows that the new theoretical approach is capable to provide accurate peak response with those obtained when using the NL-THA analysis. After that, a simplified nonlinear spectral analysis is proposed and illustrated by examples in order to describe inelastic response spectra and to relate it to the capacity curve (Pushover curve) by a new parameter of control, called normalized yield strength coefficient (${\eta}$). In the second application, the proposed procedure is verified against the NL-THA analysis results of two buildings for 80 selected real ground motions.

Generation of artificial earthquake time histories for the seismic analysis of base-isolated bridges (지진격리교량의 지진해석을 위한 인공지진파의 작성)

  • Kim, Nam-Sik;Kim, Jae-Min;Lee, Gye-Hee;Kang, Hyeong-Taek
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2005.03a
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    • pp.487-494
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    • 2005
  • In this study, a set of artificial earthquake time histories, which can be used for the earthquake-resistant design of seismically isolated highway bridges, was presented. In addition, adequateness of the generated ground accelerations was investigated. These were performed based on the seismic design standard for seismically isolated bridges. Total of 22 acceleration time histories were generated for each soil condition by the spectral method. The time histories were verified to meet the code provisions including (1) mean response spectrum at control frequencies, (2) EPGA (effective peak ground acceleration), and (3) correlation coefficient. Finally, the maximum response corresponding to four time histories and the mean response associated with seven time histories were computed using the generated acceleration time histories, which shows validity of the proposed artificial earthquake time histories.

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The effect of impact with adjacent structure on seismic behavior of base-isolated buildings with DCFP bearings

  • Bagheri, Morteza;Khoshnoudiana, Faramarz
    • Structural Engineering and Mechanics
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    • v.51 no.2
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    • pp.277-297
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    • 2014
  • Since the isolation bearings undergo large displacements in base-isolated structures, impact with adjacent structures is inevitable. Therefore, in this investigation, the effect of impact on seismic response of isolated structures mounted on double concave friction pendulum (DCFP) bearings subjected to near field ground motions is considered. A non-linear viscoelastic model of collision is used to simulate structural pounding more accurately. 2-, 4- and 8-story base-isolated buildings adjacent to fixed-base structures are modeled and the coupled differential equations of motion related to these isolated systems are solved in the MATLAB environment using the SIMULINK toolbox. The variation of seismic responses such as base shear, displacement in the isolation system and superstructure (top floor) is computed to study the impact condition. Also, the effects of variation of system parameters: isolation period, superstructure period, size of seismic gap between two structures, radius of curvature of the sliding surface and friction coefficient of isolator are contemplated in this study. It is concluded that the normalized base shear, bearing and top floor displacement increase due to impact with adjacent structure. When the distance between two structures decreases, the base shear and displacement increase comparing to no impact condition. Besides, the increase in friction coefficient difference also causes the normalized base shear and displacement in isolation system and superstructure increase in comparison with bi-linear hysteretic behavior of base isolation system. Totally, the comparison of results indicates that the changes in values of friction coefficient have more significant effects on 2-story building than 4- and 8-story buildings.

Experimental research on seismic behavior of a composite RCS frame

  • Men, Jinjie;Zhang, Yarong;Guo, Zhifeng;Shi, Qingxuan
    • Steel and Composite Structures
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    • v.18 no.4
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    • pp.971-983
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    • 2015
  • To promote greater acceptance and use of composite RCS systems, a two-bay two-story frame specimen with improved composite RCS joint details was tested in the laboratory under reversed cyclic loading. The test revealed superior seismic performance with stable load versus story drift response and excellent deformation capacity for an inter-story drift ratio up to 1/25. It was found that the failure process of the frame meets the strong-column weak-beam criterion. Furthermore, cracking inter-story drift ratio and ultimate inter-story drift ratio both satisfy the limitation prescribed by the design code. Additionally, inter-story drift ratios at yielding and peak load stage provide reference data for Performance-Based Seismic Design (PBSD) approaches for composite RCS frames. An advantage over conventional reinforced concrete and steel moment frame systems is that the displacement ductility coefficient of the RCS frame system is much larger. To conclude, the test results prove that composite RCS frame systems perform satisfactorily under simulated earthquake action, which further validates the reliability of this innovative system. Based on the test result, some suggestions are presented for the design of composite RCS frame systems.

Development of Curve Fitted Equations for Seismic Performance Evaluation of Various Buried Pipelines (각종 매설관의 내진성능평가를 위한 곡선적합식의 개발)

  • Jeong, Jin-Ho;Park, Byung-Ho;Kim, Sung-Ban
    • Proceedings of the Korean Geotechical Society Conference
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    • 2006.03a
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    • pp.1326-1333
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    • 2006
  • Purpose of this research is a development for the curve fitted equations that can improve practical calculation and work application when seismic performance has been evaluated and this work has been made a study of the dynamic response under various boundary conditions of buried pipelines to compare the dynamic behavior of concrete pipe and steel pipe, FRP pipe. This research have been developed curve fitted equations that can be improving efficiency and practicality. Using a nonlinear least square method, and after testing several different exponential equations, Proposed the curve fitted equations to give the best result and constant value by the propagation velocities. With these results, dynamic response analysis and seismic performance evaluation have been achieved on concrete pipe, steel pipe and FRP pipe that have a various boundary conditions. Degree of a polynomial expression and coefficient value by propagation velocity have been calculated when using the curve fitting equations.

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Construction of Design Table for Envelope Curve Analysis of Base Isolated Buildings (면진건물의 포락해석을 위한 설계용 도표 산정면진건물의 포락해석을 위한 설계용 도표 산정면진건물의 포락해석을 위한 설계용 도표 산정)

  • Lee, Hyun-Ho;Cheon, Yeong-Soo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.10 no.2
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    • pp.59-67
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    • 2006
  • The aim of this study is to evaluate the design table for envelope curve analysis of base isolated buildings, which represent the period of base isolated buildings and the lateral displacement of base isolation devices. For the construction of design table, $V_E$ spectrum, which represents the energy, is developed instead of acceleration of seismic hazard. Based on the seismic coefficient of UBC 97, boundary period $T_G$ and maximum velocity response $V_0$ are proposed considering Korea seismic hazard. Using $T_G$ and $V_0$, finally, $V_E$ spectrum is developed for the four types of soil conditions. Base on the $V_E$ spectrum, design table for envelope curve analysis is also developed for soil types.