국내 지진동 특성에 대한 기기 용접 정착부의 비탄성에너지 흡수계수를 고려한 지진취약도 평가

임승현,김건규,최인길,곽신영 한국지진공학회 2023 한국지진공학회논문집 Vol.27 No.1

In Korea, most nuclear power plants were designed based on the design response spectrum of Regulatory Guide 1.60 of the NRC. However, in the case of earthquakes occurring in the country, the characteristics of seismic motions in Korea and the design response spectrum differed. The seismic motion in Korea had a higher spectral acceleration in the high-frequency range compared to the design response spectrum. The seismic capacity may be reduced when evaluating the seismic performance of the equipment with high-frequency earthquakes compared with what is evaluated by the design response spectrum for the equipment with a high natural frequency. Therefore, EPRI proposed the inelastic energy absorption factor for the equipment anchorage. In this study, the seismic performance of welding anchorage was evaluated by considering domestic seismic characteristics and EPRI's inelastic energy absorption factor. In order to reflect the characteristics of domestic earthquakes, the uniform hazard response spectrum (UHRS) of Uljin was used. Moreover, the seismic performance of the equipment was evaluated with a design response spectrum of R.G.1.60 and a uniform hazard response spectrum (UHRS) as seismic inputs. As a result, it was confirmed that the seismic performance of the weld anchorage could be increased when the inelastic energy absorption factor is used. Also, a comparative analysis was performed on the seismic capacity of the anchorage of equipment by the welding and the extended bolt.

Seismic performance assessment of the precast concrete buildings using FEMA P-695 methodology

Mahdi Adibi,Roozbeh Talebkhah 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.82 No.1

The precast reinforced concrete frame system is a method for industrialization of construction. However, the seismic performance factor of this structural system is not explicitly clarified in some existing building codes. In this paper, the seismic performance factor for the existing precast concrete building frame systems with cast-in-situ reinforced shear walls were evaluated. Nonlinear behavior of the precast beam-column joints and cast-in-situ reinforced shear walls were considered in the modeling of the structures. The ATC-19’s coefficient method was used for calculating the seismic performance factor and the FEMA P-695’s approach was adopted for evaluating the accuracy of the computed seismic performance factor. The results showed that the over-strength factor varies from 2 to 2.63 and the seismic performance factor (R factor) varies from 5.1 to 8.95 concerning the height of the structure. Also, it was proved that all of the examined buildings have adequate safety against the collapse at the MCE level of earthquake, so the validity of R factors was confirmed. The obtained incremental dynamic analysis (IDA) results indicated that the minimum adjusted collapse margin ratio (ACMR) of the precast buildings representing the seismic vulnerability of the structures approximately equaled to 2.7, and pass the requirements of FEMA P-695.

콘크리트 옹벽의 지진여유도 평가

박두희,백종민,박인준,황경민,장정범 한국지반환경공학회 2019 한국지반환경공학회논문집 Vol.20 No.7

In recent Gyeongju and Pohang earthquakes, motions that exceed the design ground motion were recorded. This has led to adjustments to the design earthquake intensity in selected design guidelines. An increment in the design intensity requires reevaluation of all associated facilities, requiring extensive time and cost. Firstly, the seismic factor of safety of built concrete retaining walls are calculated. Secondly, the seismic margin of concrete retaining walls is evaluated. The design sections of concrete walls built at power plants and available site investigation reports are utilized. Widely used pseudo-static analysis method is used to evaluate the seismic performance. It is shown that all concrete walls are safe against the adjusted design ground motion. To determine the seismic margin of concrete walls, the critical accelerations, which is defined as the acceleration that causes the seismic factor of safety to exceed the allowable value, are calculated. The critical acceleration is calculated as 0.36g~0.8g. The limit accelerations are significantly higher than the design intensity and are demonstrated to have sufficient seismic margin. Therefore, it is concluded that the concrete retaining walls do not need to be reevaluated even if the design demand is increased up to 0.3g. 최근 발생한 경주지진(’16.9.12., ML=5.8) 및 포항지진(’17.11.15., ML=5.4)에서 국내의 설계지반운동 수준을 초과하는 진동이 관측되었으며 이를 계기로 설계지반운동이 일부 내진설계지침서에서 개정되었다. 설계지반운동이 조정되면 관련된 모든 시설물의 내진성능을 재평가해야 하며 이를 위해서는 막대한 시간과 비용이 소요된다. 본 연구에서는 일차적으로 조정된 설계지반운동 기준에 대한 기설된 콘크리트 옹벽의 내진성능 확보 여부를 평가하였으며 이차적으로 콘크리트 옹벽의 지진여유도를 평가하였다. 변전소 주변에 기설된 콘크리트 옹벽 단면과 지반주상도를 사용하였으며 지진에 대한 안전율은 유사정적해석법을 사용하여 계산하였다. 평가에 사용된 모든 옹벽은 조정된 설계지반운동에 대해서 충분한 성능을 확보하고 있는 것으로 나타났다. 나아가 옹벽의 지진여유도를 평가하기 위하여 기준 안전율을 만족하지 못하는 임계가속도를 계산하였다. 임계가속도는 0.36g~0.8g 범위로 설계지반운동을 크게 상회하며 콘크리트 옹벽의 지진여유도는 매우 큰 것으로 분석되었다. 따라서 추후 설계지반운동이 0.3g 이상으로 상향조정되어도 옹벽의 전면적인 재평가는 불필요할 것으로 판단된다.

소화전 함의 내진설계 최적화 방법에 관한 연구

오흥규(Oh, Heunggyoo),민세홍(Min, Sehong) 한국방재학회 2021 한국방재학회논문집 Vol.21 No.2

최근 행정안전부의 ‘내진설계기준 공통 적용사항’에 따른 개정된 ‘건축구조기준’과 ‘소방시설의 내진설계기준’으로 비구조요소인 소방시설의 지진하중과 구조안전성에 대한 중요성이 대두되고 있다. 경주(2016)와 포항(2017)에서 발생한 리히터 규모 5.0 이상의 지진 피해사례에서는 벽체와 소화전 함이 파손 또는 변형되어 문을 열 수 없는 문제가 발생하였고, 이로 인해 내진설계가 되지 않은 소화전 함과 내부기기들의 파손, 변형, 이탈로 오작동을 일으켜 화재 위험성이 증가하였다. 본 연구는 소화전 함의 내진설계 규정에 맞도록 지진하중을 산정하고, 성능은 3D Modeling과 구조해석 시뮬레이션 및 구조부재와 정착을 검토하여 구조안전성을 확인하였다. 또한, 소화전 함의 내진설계 성능 영향인자에 따라 시뮬레이션 결과를 분석·비교하여 최적화된 내진설계 방안을 제안하였다. As per the revisions to the Korean Building Code and the Seismic Design Code for fire protection systems in accordance with the Common Applications of the Seismic Design Code by the Ministry of the Interior and Safety, earthquake load and structural safety of a non-structural element are considered as important parameters for a fire protection system. In Richter scale 5.0 or higher earthquake damage cases occurring in Gyeongju (2016) and Pohang (2017), walls and hydrant boxes were broken or deformed such that their doors could not be opened. Therefore, the breakage, deformation, and detachment of hydrants and internal devices without the seismic design caused malfunction and increased the fire risk. In this study, the earthquake load was calculated according to the seismic design regulation on the hydrant box and the structural stability was verified by 3D model review, structural analysis simulation, the structural member, and the anchorage for performance. Moreover, an optimized seismic design plan was proposed by analyzing and comparing the simulation result for the factors governing the seismic design performance of a fire hydrant box.

단주효과 및 고유주기를 고려한 비내진 학교시설의 반응 수정계수

김범석,박지훈,Kim, Beom Seok,Park, Ji-Hun 한국지진공학회 2019 한국지진공학회논문집 Vol.23 No.4

Response modification factors of school facilities for non-seismic RC moment frames with partial masonry infills in 'Manual for Seismic Performance Evaluation and Retrofit of School Facilities' published in 2018 were investigated in the preceding study. However, since previous studies are based on 2D frame analysis and limited analysis conditions, additional verification needs to be performed to further apply various conditions including orthogonal effect of seismic load. Therefore, this study is to select appropriate response modification factors of school facilities for non-seismic RC moment frames with partial masonry infills by 3D frame analysis. The results are as follows. An appropriate response modification factor for non-seismic RC moment frames with partial masonry infills is proposed as 2.5 for all cases if the period is longer than 0.6 seconds. Also if the period is less than 0.4 seconds and the ratio of shear-controlled columns is less than 30%, 2.5 is chosen too. However, if the period is less than 0.4 seconds and the ratio of shear-controlled columns is higher than 30%, the response modification factor shall be reduced to 2.0. If the period is between 0.4 and 0.6 seconds, then linearly interpolates the response correction factor.

Effect of seismic design level on safety against progressive collapse of concentrically braced frames

Farshad Hashemi Rezvani,Behrouz Asgarian 국제구조공학회 2014 Steel and Composite Structures, An International J Vol.16 No.2

In this research the effect of seismic design level as a practical approach for progressive collapse mitigation and reaching desired structural safety against it in seismically designed concentric braced frame buildings was investigated. It was achieved by performing preliminary and advanced progressive collapse analysis of several split-X braced frame buildings, designed for each seismic zone according to UBC 97 and by applying various Seismic Load Factors (SLFs). The outer frames of such structures were studied for collapse progression while losing one column and connected brace in the first story. Preliminary analysis results showed the necessity of performing advanced element loss analysis, consisting of Vertical Incremental Dynamic Analysis (VIDA) and Performance-Based Analysis (PBA), in order to compute the progressive collapse safety of the structures while increasing SLF for each seismic zone. In addition, by sensitivity analysis it became possible to introduce the equation of structural safety against progressive collapse for concentrically braced frames as a function of SLF for each seismic zone. Finally, the equation of progressive collapse safety as a function of bracing member capacity was presented.

비탄성 요구도 스펙트럼을 이용한 교량구조물의 역량스펙트럼 해석에 대한 강도감소계수의 영향

송종걸(Song Jong-Keol),김학수(Jin He-Shou),장동휘(Jang Dong-Hui) 대한토목학회 2008 대한토목학회논문집 A Vol.28 No.1A

역랑스펙트럼 방법은 그래픽적인 방법으로 간단하게 지진해석을 수행한다. 개발 초기에 역량스펙트럼 방법은 빌딩구조물에 주로 사용되었으나 최근에는 교량구조물에도 사용할 수 있도록 확장되었다. 역량스펙트럼 방법은 비탄성 정적해석으로부터 구한 역량곡선과 유효감쇠 혹은 강도감소계수를 사용하여 선형탄성 설계스펙트럼을 감소시켜 구한 요구도 스펙트럼에 기반을 두고 있다. 본 논문에서는 감소된 요구도 스펙트럼은 강도감소계수에 대한 몇 개의 제안식을 사용하여 구한 비탄성 요구도 스펙트럼을 사용한다. 역량스펙트럼 해석에 대한 강도감소계수의 영향은 세가지 종류의 대칭 및 비대칭 교량에 대하여 평가하였다. 몇 개의 강도감소계수를 적용한 역량스펙트럼 방법의 정확성을 평가하기 위하여, 역량스펙트럼 방법에 의한 최대변위를 8개의 인공지진에 의한 비탄성 시간이력해석 결과와 비교하였다. 강도감소계수 제안식 중 SJ 제안식에 의한 역량 스펙트럼 해석의 최대변위가 비탄성 시간이력해석 결과와 가장 일치하는 결과를 나타냄을 알 수 있었다. The capacity spectrum method (CSM) is a simple and graphical seismic analysis procedure. Originally, it has been developed for buildings, but now its applicability has been extended to bridge structures. It is based on the capacity curve estimated by pushover analysis and demand spectrum reduced from linear elastic design spectrum by using effective damping or strength reduction factor. In this paper, the inelastic demand spectrum as the reduced demand spectrum is calculated from the linear elastic design spectrum by using the several formulas for the strength reduction factor. The effects of the strength reduction factor for the capacity spectrum analysis are evaluated for 3 types of symmetric and asymmetric bridge structures. To investigate an accuracy of the CSM which several formulas for strength reduction factor were applied, the maximum displacements estimated by the CSM are compared with the results obtained by nonlinear time history analysis for 8 artificially generated earthquakes. The maximum displacements estimated by the CSM using the SJ formula among the several strength reduction factors provide the most accurate agreement with those calculated by the inelastic time history analysis.

Performance-based design of tall buildings for wind load and application of response modification factor

Hamidreza Alinejad,정승용,Thomas K. Kang 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.31 No.2

In the design of buildings, lateral loading is one of the most important factors considered by structural designers. The concept of performance-based design (PBD) is well developed for seismic load. Whereas, wind design is mainly based on elastic analysis for both serviceability and strength. For tall buildings subject to extreme wind load, inelastic behavior and application of the concept of PBD bear consideration. For seismic design, current practice primarily presumes inelastic behavior of the structure and that energy is dissipated by plastic deformation. However, due to analysis complexity and computational cost, calculations used to predict inelastic behavior are often performed using elastic analysis and a response modification factor (R). Inelastic analysis is optionally performed to check the accuracy of the design. In this paper, a framework for application of an R factor for wind design is proposed. Theoretical background on the application and implementation is provided. Moreover, seismic and wind fatigue issues are explained for the purpose of quantifying the modification factor R for wind design.

Performance-based reliability assessment of RC shear walls using stochastic FE analysis

Arina Nosoudi,Hooshang Dabbagh,Azad Yazdani 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.6

Performance-based reliability analysis is a practical approach to investigate the seismic performance and stochastic nonlinear response of structures considering a random process. This is significant due to the uncertainties involved in every aspect of the analysis. Therefore, the present study aims to evaluate the performance-based reliability within a stochastic finite element (FE) framework for reinforced concrete (RC) shear walls that are considered as one of the most essential elements of structures. To accomplish this purpose, deterministic FE analyses are conducted for both squat and slender shear walls to validate numerical models through experimental results. The presented numerical analysis is performed by using the ABAQUS FE program. Afterwards, a random-effects investigation is carried out to consider the influence of different random variables on the lateral load-top displacement behavior of RC members. Using these results and through utilizing the Monte-Carlo simulation method, stochastic nonlinear analyses are also performed to generate random FE models based on input parameters and their probabilistic distributions. In order to evaluate the reliability of RC walls, failure probabilities and corresponding reliability indices are calculated at life safety and collapse prevention levels of performance as suggested by FEMA 356. Moreover, based on reliability indices, capacity reduction factors are determined subjected to shear for all specimens that are designed according to the ACI 318 Building Code. Obtained results show that the lateral load and the compressive strength of concrete have the highest effects on load-displacement responses compared to those of other random variables. It is also found that the probability of shear failure for the squat wall is slightly lower than that for slender walls. This implies that β values are higher in a nonductile mode of failure. Besides, the reliability of both squat and slender shear walls does not change significantly in the case of varying capacity reduction factors.

Newmark & Hall의 응답스펙트럼을 이용한 완전탄소성 구조물의 내진성능 및 요구감쇠비 산정법

김형국(Kim, Hyeong-Gook),김길희(Kim, Kil-Hee) 대한건축학회 2016 大韓建築學會論文集 : 構造系 Vol.32 No.2

An estimation method for seismic performance and damping requirement of elastic perfectly plastic structures is proposed in this paper. To assess the seismic performance of structures without iterative analysis and non-convergence problems of the capacity spectrum method, the capacity curve and the demand spectrum are assumed to be functions of the ductility factor. The damping requirement to achieve a prescribed performance target is evaluated using the relationship between the amplification factors in Newmark & Hall’s response spectrum and a prescribed inelastic displacement. Time history response analysis is carried out and the results are compared with those obtained using the proposed method to confirm its validity. The analytical results shown that, if the ductility value is less than 6 for elastic perfectly plastic structures, the proposed method is effective at estimating seismic performance and damping requirement of structures, using a single process during the preliminary design phase for building structures or damping devices.