• Title/Summary/Keyword: Amplification factor

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Seismic behavior investigation of the steel multi-story moment frames with steel plate shear walls

  • Mansouri, Iman;Arabzadeh, Ali;Farzampour, Alireza;Hu, Jong Wan
    • Steel and Composite Structures
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    • v.37 no.1
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    • pp.91-98
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    • 2020
  • Steel plate shear walls are recently used as efficient seismic lateral resisting systems. These lateral resistant structures are implemented to provide more strength, stiffness and ductility in limited space areas. In this study, the seismic behavior of the multi-story steel frames with steel plate shear walls are investigated for buildings with 4, 8, 12 and 16 stories using verified computational modeling platforms. Different number of steel moment bays with distinctive lengths are investigated to effectively determine the deflection amplification factor for low-rise and high-rise structures. Results showed that the dissipated energy in moment frames with steel plates are significantly related to the inside panel. It is shown that more than 50% of the dissipated energy under various ground motions is dissipated by the panel itself, and increasing the steel plate length leads to higher energy dissipation capability. The deflection amplification factor is studied in details for various verified parametric cases, and it is concluded that for a typical multi-story moment frame with steel plate shear walls, the amplification factor is 4.93 which is less than the recommended conservative values in the design codes. It is shown that the deflection amplification factor decreases if the height of the building increases, for which the frames with more than six stories would have less recommended deflection amplification factor. In addition, increasing the number of bays or decreasing the steel plate shear wall length leads to a reduction of the deflection amplification factor.

Evaluating the reliability of using the deflection amplification factor to estimate design displacements with accidental torsion effects

  • Lin, Jui-Liang;Wang, Wei-Chun;Tsai, Keh-Chyuan
    • Earthquakes and Structures
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    • v.8 no.2
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    • pp.443-462
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    • 2015
  • Some model building codes stipulate that the design displacement of a building can be computed using the elastic static analysis results multiplied by the deflection amplification factor, $C_d$. This approach for estimating the design displacement is essential and appealing in structural engineering practice when nonlinear response history analysis (NRHA) is not required. Furthermore, building codes stipulate the consideration of accidental torsion effects using accidental eccentricity, whether the buildings are symmetric-plan, or asymmetric-plan. In some model building codes, the accidental eccentricity is further amplified by the torsional amplification factor $A_x$ in order to minimize the discrepancy between statically and dynamically estimated responses. Therefore, this warrants exploration of the reliability of statically estimated design displacements in accordance with the building code requirements. This study uses the discrepancy curves as a way of assessing the reliability of the design displacement estimates resulting from the factors $C_d$ and $A_x$. The discrepancy curves show the exceedance probabilities of the differences between the statically estimated design displacements and NRHA results. The discrepancy curves of 3-story, 9-story, and 20-story example buildings are investigated in this study. The example buildings are steel special moment frames with frequency ratios equal to 0.7, 1.0, 1.3, and 1.6, as well as existing eccentricity ratios ranging from 0% to 30%.

Evaluating the effective spectral seismic amplification factor on a probabilistic basis

  • Makarios, Triantafyllos K.
    • Structural Engineering and Mechanics
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    • v.42 no.1
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    • pp.121-129
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    • 2012
  • All contemporary seismic Codes have adopted smooth design acceleration response spectra, which have derived by statistical analysis of many elastic response spectra of natural accelerograms. The above smooth design spectra are characterized by two main branches, an horizontal branch that is 2.5 times higher than the peak ground acceleration, and a declining parabolic branch. According to Eurocode EN/1998, the period range of the horizontal, flat branch is extended from 0.1 s, for rock soils, up to 0.8 s for softer ones. However, from many natural recorded accelerograms of important earthquakes, the real spectral amplification factor appears to be much higher than 2.5 and this means that the spectrum leads to an unsafe seismic design of the structures. This point is an issue open to question and it is the object of the present study. In the present paper, the spectral amplification factor of the smooth design acceleration spectra is re-calculated on the grounds of a known "reliability index" for a desired probability of exceedance. As a pilot scheme, the seismic area of Greece is chosen, as it is the most seismically hazardous area in Europe. The accelerograms of the 82 most important earthquakes, which have occurred in Greece during the last 38 years, are used. The soil categories are taken into account according to EN/1998. The results that have been concluded from these data are compared with the results obtained from other strong earthquakes reported in the World literature.

An efficient method for reliable optimum design of trusses

  • Dizangian, Babak;Ghasemi, Mohammad Reza
    • Steel and Composite Structures
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    • v.21 no.5
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    • pp.1069-1084
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    • 2016
  • This paper introduces a new and effective design amplification factor-based approach for reliable optimum design of trusses. This paper may be categorized as in the family of decoupled methods that aiming for a reliable optimum design based on a Design Amplification Factor (DAF). To reduce the computational expenses of reliability analysis, an improved version of Response Surface Method (RSM) was used. Having applied this approach to two planar and one spatial truss problems, it exhibited a satisfactory performance.

A Study of Displacement Amplification Factors Considering Hysteretic Behavior of Structural Systems and Earthquake Characteristics (비탄성 이력응답 및 지진특성을 반영한 변위증폭계수에 관한 연구)

  • Song, Jong-Keol;Kim, Hark-Soo
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2007.04a
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    • pp.777-782
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    • 2007
  • Displacement amplification factor can be used to estimate inelastic displacement demands from elastic displacement demands, The simple formula for displacement amplification factor considering hysteretic behavior of structural system and earthquake characteristics is proposed. And the effects of several parameters such as displacement ductility, strain hardening ratio, period, characteristics of earthquakes and hysteretic models for the displacement amplification factor are evaluated. Accuracy of the proposed formula is evaluated by comparing the displacement amplification factors estimated by existing and proposed formula with those calculated from inelastic time history analysis. The displacement amplification factors by proposed formulas provide a good agreement with those calculated by inelastic time history analysis.

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Verification of the Torsional Amplification Factor for the Seismic Design of Torsionally Imbalanced Buildings (비틀림 비정형 건물의 내진설계를 위한 우발편심 비틀림 증폭계수 검증)

  • Lee, Kwang-Ho;Jeong, Seoung-Hoon
    • Journal of the Earthquake Engineering Society of Korea
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    • v.14 no.6
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    • pp.67-74
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    • 2010
  • Because of the difference between the actual and computed eccentricity of buildings, symmetrical buildings will be affected by torsion. In provisions, accidental eccentricity is intended to cover the effect of several factors, such as unfavorable distributions of dead- and live-load masses and the rotational component of ground motion about a vertical axis. The torsional amplification factor is introduced to reduce the vulnerability of torsionally imbalanced buildings. The effect of the torsional amplification factor is observed for a symmetric rectangular building with various aspect ratios, where the seismic-force-resisting elements are positioned at a variable distance from the geometrical center in each direction. For verifying the torsional amplification factor in provisions, nonlinear reinforced concrete models with various eccentricities and aspect ratios are used in rock. The difference between the maximum displacements of the flexible edge obtained between using nonlinear static and time-history analysis is very small but the difference between the maximum torsional angles is large.

Study on the Seismic Performance for Low-rised RC Building with Vertical and Torsional Irregularities (수직비정형과 비틀림비정형을 동시에 가지는 저층 RC 건물의 내진성능에 관한 연구)

  • Choi, In-Hyuk;Baek, Eun-Rim;Lee, Sang-Ho
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.35 no.12
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    • pp.137-148
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    • 2019
  • Korean piloti-type buildings are comprised of pilotis in the first story and shear walls in the upper stories. This vertical irregularity causes excessive lateral plastic deformation on the first story while the upper stories stay elastic. Meanwhile, asymmetric position of structural components such as core walls and columns of RC piloti-type buildings tends to produce torsional irregularities of the structures. Korean Building Code(KBC2016) requires the special seismic load and torsional amplification factor to apply to the piloti-type buildings lower than six-story or 20m if it has vertical and torsional irregularities when the building corresponds to seismic design category C or D. Many Korean low-rised RC buildings fall into the class. Therefore, the special earthquake load and torsional amplification factor are often applied to a building simultaneously. However, it has not been studied enough how much influence each parameter has on buildings with vertical and torsional irregularities at the same time. The purpose of this study is to evaluate the effect of factor special seismic load and torsional amplification on seismic performance of irregular buildings. In this study, a damaged 4th story piloti-type building by the Pohang earthquake was selected and the earthquake response analysis was carried out with various seismic design methods by the KBC 2016. The effect of the design parameters on seismic performance was analyzed by the dynamic analysis of models with special seismic load and torsional amplification factor based on the selected building. It was concluded that the application of the torsional amplification factor to the reference model to which special seismic design was applied, does not significantly affect the seismic performance.

Estimation of Dynamic Load Amplification Factors under Various Roughness Indices and Vehicle Classes (주행차량의 종류와 아스팔트 콘크리트 포장 평탄성에 따른 동적하중 증가계수 산정)

  • Choi, Jun-Seong;Seo, Joo-Won;Kim, Jong-Woo
    • International Journal of Highway Engineering
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    • v.14 no.2
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    • pp.29-36
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    • 2012
  • In this study, frequently passing vehicles with two, three, four, and five axles were chosen through traffic volume analysis in Kyung-In Expressway in order to analyze how the road roughness and vehicle speed affect on the dynamic loads for roads in various vehicle classes. Dynamic loads according to chosen vehicles are estimated by TruckSim program. Dynamic load amplification factor is ratio between dynamic and static loads, and it is also determined for each vehicle classes. From the result of dynamic loads estimated by the dynamic load amplification factor, it is shown that for three-axles vehicle, when IRI is 3.5 and vehicle speed is 100km/hr, asphalt pavements receive additional 36% of static loads in maximum. The analysis of the amplification factor according to each vehicle classes also indicates that the amplification factor increases as the distance between the axles becomes smaller and each axle receives more loads.

Seismic Response Amplification Factors of Nuclear Power Plants for Seismic Performance Evaluation of Structures and Equipment due to High-frequency Earthquakes (구조물 및 기기의 내진성능 평가를 위한 고주파수 지진에 의한 원자력발전소의 지진응답 증폭계수)

  • Eem, Seung-Hyun;Choi, In-Kil;Jeon, Bub-Gyu;Kwag, Shinyoung
    • Journal of the Earthquake Engineering Society of Korea
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    • v.24 no.3
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    • pp.123-128
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    • 2020
  • Analysis of the 2016 Gyeongju earthquake and the 2017 Pohang earthquake showed the characteristics of a typical high-frequency earthquake with many high-frequency components, short time strong motion duration, and large peak ground acceleration relative to the magnitude of the earthquake. Domestic nuclear power plants were designed and evaluated based on NRC's Regulatory Guide 1.60 design response spectrum, which had a great deal of energy in the low-frequency range. Therefore, nuclear power plants should carry out seismic verification and seismic performance evaluation of systems, structures, and components by reflecting the domestic characteristics of earthquakes. In this study, high-frequency amplification factors that can be used for seismic verification and seismic performance evaluation of nuclear power plant systems, structures, and equipment were analyzed. In order to analyze the high-frequency amplification factor, five sets of seismic time history were generated, which were matched with the uniform hazard response spectrum to reflect the characteristics of domestic earthquake motion. The nuclear power plant was subjected to seismic analysis for the construction of the Korean standard nuclear power plant, OPR1000, which is a reactor building, an auxiliary building assembly, a component cooling water heat exchanger building, and an essential service water building. Based on the results of the seismic analysis, a high-frequency amplification factor was derived upon the calculation of the floor response spectrum of the important locations of nuclear power plants. The high-frequency amplification factor can be effectively used for the seismic verification and seismic performance evaluation of electric equipment which are sensitive to high-frequency earthquakes.

Shaking Table Test on the Piloti-type RC Frames with Horizontal Irregularity (수평비정형을 갖는 필로티형 RC 골조의 진동대 실험)

  • Jeon, Ho-Gyeong;Baek, Eun-Rim;Lee, Sang-Ho
    • Journal of the Architectural Institute of Korea
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    • v.37 no.8
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    • pp.177-188
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    • 2021
  • Most of domestic low-rised buildings with piloti-type have both vertical and horizontal irregularities. In KDS 41 17 00 : 2019, when using the equivalent static analysis method for vertical and horizontal irregular buildings, the special seismic load combination and torsional amplification factor should be applied to the seismic design. However, it is independently introduced without considering the case where both design methods are applied at the same time, and the basis and relevant research are insufficient. Therefore, it is necessary to understand the effect of the special seismic load and torsional amplification factor on the seismic design of building having both vertical and horizontal irregularities. The purpose of this study is to evaluate the seismic performance of the piloti-type building according to the application of special seismic load and torsional amplification factor when designing a building with both vertical and horizontal irregularities. The specimen A that did not apply both the special seismic load and torsional amplification factor and the specimen B that applied only the special seismic load, were designed and fabricated, and the failure mode and behavior were identified through the shaking table tests. As the results of the shaking table test, in the final stage of the specimen A, the failure occurred at the upper and lower joints of the column farthest from the core wall, and the specimen B did not fail or collapse. In addition, it was confirmed that the torsional behavior was relatively controlled even when only the special seismic load was considered.