• Steel and Composite Structures
• /
• 제37권6호
• /
• pp.679-693
• /
• 2020

This paper investigates the seismic response of buildings equipped with Self-Centering Energy Dissipating (SCED) braces. Two-dimensional models of 3, 6, 12 and 16-story SCED buildings considering both material and geometric nonlinearities are investigated by carrying out pushover and nonlinear time-history analyses. The response indicators of the buildings are studied for weight-scaled ground motions to represent the Design Basis Earthquake (DBE) level and the Maximum Considered Earthquake (MCE) event. The fragility curves of the buildings for two Immediate Occupancy (IO) and Life Safety (LS) performance levels are developed using Incremental Dynamic Analysis (IDA). Results of the nonlinear response history analyses indicate that the maximum inter-story drift occurs at the taller buildings. The mean peak inter-story drift is less than 2% in both hazard levels. High floor acceleration peaks are observed in all the SCED frames regardless of the building height. The overall ductility and ductility demand increase when the number of stories reduces. The results also showed the residual displacement is negligible for all of case study buildings. The 3 and 6-story buildings exhibit desirable performance in IO and LS performance levels according to fragility curves results, while 12 and 16-story frames show poor performance especially in IO level. The results indicated the SCED braces performance is generally better in lower-rise buildings.

• Earthquakes and Structures
• /
• 제21권6호
• /
• pp.601-612
• /
• 2021

The paper concerns the selection of a design accelerograms used for the slope stability assessment under earthquake excitation. The aim is to experimentally verify the Arias Intensity as an indicator of the excitation threat to the slope stability. A simple dynamic system consisting of a rigid block on a rigid inclined plane subjected to horizontal excitation is adopted as a slope model. Strong ground motions recorded during earthquakes are reproduced on a shaking table. The permanent displacement of the block serves as a slope stability indicator. Original research stand allows us to analyse not only the relative displacement but also the acceleration time history of the block. The experiments demonstrate that the Arias Intensity of the accelerogram is a good indicator of excitation threat to the stability of the slope. The numerical analyses conducted using the experimentally verified extended Newmark's method indicate that both the Arias Intensity and the peak velocity of the excitation are good indicators of the impact of dynamic excitation on the dam's stability. The selection can be refined using complementary information, which is the dominant frequency and duration of the strong motion phase of the excitation, respectively.

• Earthquakes and Structures
• /
• 제23권1호
• /
• pp.75-85
• /
• 2022

The megacity Istanbul was struck by an earthquake on September 26, 2019, with a moment magnitude (Mw) of 5.8. The mainshock was followed by many aftershocks. Although the peak ground acceleration (PGA) of the mainshock was as low as 0.08 g, its effect has been more than expected. The intensive reconnaissance studies were accomplished in the highly populated Zeytinburnu and Pendik districts of Istanbul. While the earthquake (EQ) was relatively smaller concerning record-specific intensity measures; the damages such as concrete spalling in reinforced concrete (RC) members, detachment and diagonal cracking of infill walls in RC frames as well as cracks in masonry structures were reported from non-engineered and some engineered buildings. Many studies in the literature state that record-specific intensity measures are not sufficient to evaluate the seismic performance of the structures. The structure-specific intensity measures, soil characteristics, as well as significant duration, energy, and frequency content of EQs should be considered for the evaluation. Dependently, the frequency and energy contents of the Istanbul Earthquake are evaluated to discuss the possible reasons for the perceived effects and the damages. It is concluded that the EQ caused resonance effects on a variety of structures because of its complex frequency content as well as rather low building quality.

• Structural Engineering and Mechanics
• /
• 제81권5호
• /
• pp.591-606
• /
• 2022

When the friction pendulum system and shear keys work together to resist the ground motion, which inclined inputs (non 45°) to the bridge structure, the shear keys in XY direction will be sheared asynchronously, endowed the friction pendulum system with a violent curvilinear motion on the sliding surface during earthquakes. In view of this situation, firstly, this paper abandons the equivalent linearization model of friction and constructs a Spring-Coulomb friction plane isolation system with XY shear keys, and then makes a detailed mechanical analysis of the movement process of friction pendulum system, next, this paper establishes the mathematical model of structural time history response calculation by using the step-by-step integration method, finally, it compiles the corresponding computer program to realize the numerical calculation. The results show that the calculation method in this paper takes advantage of the characteristic that the friction force is always µmg, and creatively uses the "circle making method" to express the change process of the friction force and resultant force of the friction pendulum system in any calculation time step, which can effectively solve the temporal nonlinear action of the plane friction; Compared with the response obtained by the calculation method in this paper, the peak values of acceleration response and displacement response calculated by the unidirectional calculation model, which used in the traditional research of the friction pendulum system, are smaller, so the unidirectional calculation model is not safe.

• Earthquakes and Structures
• /
• 제24권5호
• /
• pp.377-391
• /
• 2023

The high seismic risk has once again revealed in Türkiye with two major earthquakes that occurred on 06.02.2023, which took its place among the most destructive earthquakes in the last century. Totally, 65 earthquakes that occurred in the historical period in Türkiye were taken into account within the scope of this study. The seismic parameters were compared by considering the last two earthquake hazard maps for the epicenters of these earthquakes. Earthquake Intensity (I) of historical earthquakes were converted to Peak Ground Acceleration (PGA) by using suggested relations. Structural analyzes were performed for a sample reinforced-concrete building by using the obtained PGA's and predicted PGA's in the last two earthquake hazard maps. In the structural analysis, two different material groups such as low (C12-S220) and normal (C25-S420) were selected. As the material strength increased, the period value decreased, while the seismic capacity and stiffness increased. It has been determined that there are differences between the measured and proposed seismic risks for some earthquakes, and as a result, there are significant differences between the expected target displacement values from the structures. Therefore, it will not be possible to estimate the damage and to determine the building performance realistically. The main purpose of the study is to reveal whether the earthquake risk is adequately represented on seismic and structural parameters.

• 터널과지하공간
• /
• 제24권5호
• /
• pp.354-365
• /
• 2014

2005년 3월 20일 규모 6.5의 후쿠오카 본진이 발생하였고 이후 발생한 규모 3.7 이상의 15 개 중규모 후쿠오카 지진으로부터 관측된 지반진동 파형을 이용하여 수평 응답스펙트럼을 분석하였다. 결과를 국내 원자력 관련 구조물의 내진설계 기준과 국내 일반 구조물 및 건축물 내진설계기준과 각각 비교하였다. 수평성분 178개 지반진동을 이용하여 고유진동수별 지반응답을 구하고 최대 지반 가속도 값을 이용하여 정규화 분석을 수행하였다. 연구결과는 응답값에 대한 진앙거리 의존성이 대단히 크다는 것을 보여주었다. 또한 국내 원자력시설물의 내진기준인 Regulatory Guide 1.60과 비교한 결과는 일부 구간 즉 약 8 ~ 10 Hz 구간과 약 16 ~ 20 Hz의 2개의 구간에서 표준편차를 더한 값이 Regulatory Guide 1.60 보다 약간 초과함을 보여 주었다. 또한 국내 일반 구조물 및 건축물 내진설계 응답스펙트럼을 3 개 지반조건에 적용한 결과는 거의 모든 주기 대역에서 분석된 응답스펙트럼이 SE 지반조건의 설계 응답스펙트럼(500년 재래주기, 지진구역 1, SE 지반조건)을 초과하고 있다. 500년 재래주기는 가장 약한 내진 설계기준에 해당하기 때문에 거의 모든 주기 대역에서 본 연구로부터 분석된 응답스펙트럼이 해당 기준을 초과하고 있다. 신뢰성을 보다 증가시키기 위해 향후 한반도 및 한반도 주변 해외 발생지진으로부터 관측된 지진자료를 대폭적으로 보강하여 관측 지진자료의 다양성을 유지하는 것이 필요하다.

• 대한토목학회논문집
• /
• 제8권1호
• /
• pp.77-85
• /
• 1988

본 연구(硏究)에서는 지진(地震)하중을 받는 선형비례감쇠(線形比例減衰) 시스템의 층응답(層應答) 스펙트럼을 random vibration 이론(理論)을 적용하여 계산(計算)하는 방법을 제시(提示)하였다. 해석(解析)방법으로는 모드가속도법(加速度法)을 사용하였으며 구조물(構造物)-기기(機器)의 상호작용(相互作用)은 고려하지 않았다. 입력지진운동(入力地震運動)과 기기(機器)의 응답(應答)을 평균(平均)값이 영(零)인 정상(定常) Gauss 과정(過程)으로 가정하였다. 입력지진(入力地震)의 천이특성을 Vanmarcke 방법(方法)에 따라 첨두계수(尖頭係數) 계산시 고려하였다. 층응답(層應答) 스펙트럼을 공진(共振)과 비공진(非共振)으로 구분(區分)하여 계산하였으며 응답(應答)계산시 구조물(構造物)과 진동체(振動體)의 첨두계수(尖頭係數)는 지반응답(地盤應答) 스펙트럼의 첨두계수(尖頭係數)와 동일(同一)하다고 가정하였다. 적용예(適用例)에서는 시간이력해석(時間履歷解析)의 결과와 비교(比較)함으로써 본 연구(硏究)의 타당성(妥當性)을 입증(立證)하였다. 본(本) 논문(論文)의 해석방법(解析方法)을 사용(使用)하면 비교적(比較的) 정확(正確)한 안전측(安全側)의 결과(結果)를 얻을 수 있으며 시간이력해석법(時間履歷解析法)에 비해 계산시간(計算時間)을 상당(相當)히 절약할 수 있다.

• 한국지진공학회논문집
• /
• 제11권4호
• /
• pp.1-11
• /
• 2007

This paper verifies the difference of the seismic behavior and seismic damage of the neighboring two reinforced concrete piers damaged by the 1995 Hyogoken Nanbu earthquake. The two piers were almost the same size, carrying slightly different dead load, and were provided with the same reinforcement arrangement except the amount of longitudinal reinforcement at the bottom portion of the piers. The pier with more reinforcement was completely collapsed due to this near field earthquake by shear failure at the longitudinal reinforcement cut-off while the other was only damaged at the bottom by flexure even though the longitudinal reinforcement cut-off was also existed at the mid height of the pier. According to the results of the pseudo dynamic test, the seismic damage was recognized to be greatly dependent on the ground motion characteristics even though the employed ground motions had the same peak acceleration. The severe damage was observed when the test employed the seismic wave that had strong influence to the longer period range compared to the initial natural period of the pier. On the other hand, based on the similar model experiment, the defect of gas-pressure welded splice of longitudinal reinforcement was revealed to save the piers against collapse due to the so-called fail-safe mechanism contrary to the intuitive opinion of some researchers. It was concluded that the primary cause of the collapse of the pier was the extremely strong intensity and peculiar characteristics of the earthquake motion according to both the site-specific and the structure-specific effects.

• 한국전문물리치료학회지
• /
• 제14권4호
• /
• pp.44-49
• /
• 2007

The purpose of this study was to investigate the effects of auditory cues in the form of a metronome on gait initiation (GI) in Parkinson's disease (PD). 2 patients (mean age: 54 yrs) with idiopathic PD participated in the study. All patients (Hoehn and Yahr disability score of 2.0) were tested in the "on" state approximately 1.5 hours following the administration and fully responding to their PD medications. Subjects first initiated walking at self-initiated speeds to determine their cadences. Then, subjects were asked to initiate gait along the walkway while keeping pace with a metronome. The metronome rate (in beats/min) was set at a cadence 85% (slow condition), 100% (normal condition) and 115% (fast condition) of gait for each subject. Subjects were able to increase the speed of GI with faster cadence, but the speed of GI for the slow condition was similar to that of the normal condition. Swing toe-off was 578.3 ms for the fast condition, 709.4 ms for the normal condition and 736.2 ms for the slow condition. Respective times for swing heel-strike were 894.3 ms, 1110.2 ms and 1119.1 ms, and stance toe-off were 1105.4 ms, 1338.5 ms, and 1343.1 ms. Except for stance unloading ground reaction forces were greatest for the fast condition and smallest for the slow condition. It appears that PD patients were able to modulate GRFs and temporal events in response to auditory cues to achieve the peak acceleration force of the swing and stance limb. The findings from this study provided preliminary data, which could be used to investigate how PD patients modulate GRFs and temporal events during GI in response to tasks.

• 한국전산구조공학회논문집
• /
• 제29권5호
• /
• pp.413-419
• /
• 2016

지진시 사회 인프라시설물의 피해는 시설물 자체의 피해보다 사회 전반에 걸친 2차 피해를 야기한다. 그 중, 지하 공동구 구조물은 통신, 가스, 전기 등 사회의 라이프라인에 해당하여 지진에 대한 취약성을 정확히 평가하여야 할 필요가 있다. 따라서, 본 연구에서는 지하 공동구의 지진 발생 지반가속도에 따른 파괴가능성을 평가하였다. 평가를 위한 입력지반운동은 해외 실측 지진데이터와 한반도에서 발생가능한 인공지진파를 차용하였으며, 지진해석 방법은 응답변위법과 시간이력해석법을 사용하였다. 파괴여부를 판별하는 한계상태는 휨모멘트와 전단 파괴를 바탕으로 하였다. 취약도 함수 도출을 위한 방법은 최우도법이 사용되었으며, 그 분포함수는 대수정규분포로 가정하였다. 이는 지진시 지하 공동구 시설물의 피해 평가는 물론 지하 공동구 시설물의 내진설계를 위한 기초자료로 활용될 수 있다.