• Earthquakes and Structures
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• 제1권2호
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• pp.197-214
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• 2010

The paper presents a methodology for developing earthquake damage and loss scenarios for urban areas, as well as its application to two cities located in Mediterranean countries, Grevena (in Greece) and D$\ddot{u}$zce (in Turkey), that were struck by strong earthquakes in the recent past. After compiling the building inventory in each city, fragility curves were derived using a hybrid approach previously developed by the authors, and a series of seismic scenarios were derived based on microzonation studies that were specifically conducted for each city (see companion paper by Pitilakis et al.). The results obtained in terms of damage estimates, required restoration times and the associated costs are presented in a GIS environment. It is deemed that both the results obtained, and the overall methodology and tools developed, contribute towards the enhancement of seismic safety in the Mediterranean area (as well as other earthquake-prone regions), while they constitute a useful pre-earthquake decision-making tool for local authorities.

• 대한원격탐사학회지
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• 제37권1호
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• pp.13-22
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• 2021

The ML 5.8 earthquake shocked Gyeongju, Korea, at 11:32:55 UTC on September 12, 2016. One year later, on the afternoon of November 15, 2017, the ML 5.4 earthquake occurred in Pohang, South Korea. The earthquakes injured many residents, damaged buildings, and affected the economy of Gyeongju and Pohang. The damage proxy maps (DPMs) were generated from Sentinel-1 synthetic aperture radar (SAR) imagery by comparing pre- and co-events interferometric coherences to identify anomalous changes that indicate damaged by the earthquakes. DPMs manage to detect coherence loss in residential and commercial areas in both Gyeongju and Pohang earthquakes. We found that our results show a good correlation with the Korea Meteorological Administration (KMA) report with Modified Mercalli Intensity (MMI) scale values of more than VII (seven). The color scale of Sentinel-1 DPMs indicates an increasingly significant change in the area covered by the pixel, delineating collapsed walls and roofs from the official report. The resulting maps can be used to assess the distribution of seismic damage after the Gyeongju and Pohang earthquakes and can also be used as inventory data of damaged buildings to map seismic vulnerability using machine learning in Gyeongju or Pohang.

• 한국구조물진단유지관리공학회 논문집
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• 제12권1호
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• pp.175-182
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• 2008

지진에 대한 구조물의 위험도를 해석하는 경우, 여러 위험 단계에 대한 구조물의 취약도를 확인할 필요가 있다. 그리고, 교량과 같은 구조물은 지진에 저항하는 능력을 가져야하므로, 지진 격리장치가 있는 경우와 없는 경우에 대해 지진에 대한 손상 해석을 할 필요가 있다. 본 논문에서는 지진의 영향으로 최대지반가속도(PGA), 최대지반속도(PGV), 스펙트럼가속도(SA), 스펙트럼속도(SV), 스펙트럼강도(SI) 등의 특성을 고려하여, 내진 능력을 확보하기 위하여 납면진 받침을 갖는 교량의 손상도 곡선을 구하고, 탄성계수의 변화에 따른 이들 손상도 곡선의 안정성을 평가하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제13권2호통권54호
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• pp.145-152
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• 2009

지진에 대한 구조물의 위험도를 해석하는 경우, 여러 위험 단계에 대한 구조물의 취약도 또는 손상도를 확인할 필요가 있다. 그리고, 교량과 같은 구조물은 지진에 저항하는 능력을 가져야하므로, 지진 격리장치가 있는 경우와 없는 경우에 대해 지진에 대한 손상 해석을 할 필요가 있다. 본 논문에서는 지진의 영향으로 최대지반가속도(PGA), 최대지반속도(PGV), 스펙트럼가속도(SA), 스펙트럼속도(SV), 스펙트럼강도(SI) 등의 특성을 고려하여, 납면진 받침을 갖는 교량의 손상도 곡선을 구하고, 입력 지진의 변화에 따른 이들 손상도 곡선의 안정성을 평가하였다.

• 한국방재학회 논문집
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• 제7권5호
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• pp.139-150
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• 2007

컴퓨터 기술이 급속히 발전됨에 따라, 최근에는 많은 분야에서 지리정보시스템(GIS)이 활용되고 있다. 이 연구에서는 서울 내의 한 시범 지역을 대상으로 지하 지반 조건에 따라 영향을 받는 부지 효과에 관련된 지진피해 가능성을 GIS 기법을 이용하여 평가하였다. 시범 지역에서의 지역적 부지고유 지진 응답의 평가를 위하여 서울 대도시 지역에 대한 기존 시추 조사 자료의 분포를 파악하였다. GIS 토대의 지반 정보 시스템(GTIS)을 구축하여 시범 지역 전체에 대한 공간 지층 정보를 예측하였다 서울 시법 지역의 부지고유 지진응답 예측을 위한 부지 주기$(T_G)$의 정밀구역화를 GTIS 내에서 수행하였다. 공간 분포 정밀구역화 지도로부터 시범 지역 내 2 층에서 4 층 건물들의 지진 취약성을 확인하였다. 또한, GTIS 내에서 $T_G$ 분포를 토대로 설계 지반 운동 결정을 위한 지반 분류 지도를 작성하였으며, 그로부터 대상 시범 지역 부지의 거의 대부분이 현행 지반 분류 C 와 D로 분류됨을 확인하였다. 이와 같은 서울 시범 지역에 대한 지진 정밀구역화 적용 구조 체계는 특별히 기존 시추 자료를 활용하여 대도시 서울 지역 전체에 대해 적용 가능할 것으로 판단된다.

• Smart Structures and Systems
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• 제4권2호
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• pp.221-232
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• 2008

This paper represents the final results of a research program sponsored by the European Commission through project WIND-CHIME ($\underline{W}$ide Range Non-$\underline{IN}$trusive $\underline{D}$evices toward $\underline{C}$onservation of $\underline{HI}$storical Monuments in the $\underline{ME}$diterranean Area), in which the possibility of using advanced seismic protection technologies to preserve historical monuments in the Mediterranean area is investigated. In the current research, the dynamic characteristics of two outstanding Mamluk-Style minarets, which similar minarets were reported to experience extensive damage during Dahshur 1992 earthquake, are investigated. The first minaret is the Qusun minaret (1337 A.D, 736 Hijri Date (H.D)) located in El-Suyuti cemetery on the southern side of the Salah El-Din citadel. The minaret is currently separated from the surrounding building and is directly resting on the ground (no vaults underneath). The total height of the minaret is 40.28 meters with a base rectangular shaft of about 5.42 ${\times}$ 5.20 m. The second minaret is the southern minaret of Al-Sultaniya (1340 A.D, 739 H.D). It is located about 30.0 meters from Qusun minaret, and it is now standing alone but it seems that it used to be attached to a huge unidentified structure. The style of the minaret and its size attribute it to the first half of the fourteenth century. The minaret total height is 36.69 meters and has a 4.48 ${\times}$ 4.48 m rectangular base. Field investigations were conducted to obtain: (a) geometrical description of the minarets, (b) material properties of the minarets' stones, and (c) soil conditions at the minarets' location. Ambient vibration tests were performed to determine the modal parameters of the minarets such as natural frequencies and mode shapes. A $1/16^{th}$ scale model of Qusun minaret was constructed at Cairo University Concrete Research Laboratory and tested under free vibration with and without SMA wire dampers. The contribution of SMA wire dampers to the structural damping coefficient was evaluated under different vertical loads and vibration amplitudes. Experimental results were used along with the field investigation data to develop a realistic 3-D finite element model that can be used for seismic risk evaluation of the minarets. Examining the updated finite element models under different seismic excitations indicated the vulnerability of such structures to earthquakes with medium to high a/v ratio. The use of SMA wire dampers was found feasible for reducing the seismic risk for this type of structures.

• Geomechanics and Engineering
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• 제16권4호
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• pp.435-448
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• 2018

In order to make reliable earthquake-resistant design of civil engineering structures, one of the most important considerations in a region with high seismicity is to pay attention to the local soil condition of regions. It is aimed in the current study at specifying dynamic soil characteristics of Kirikkale city center conducting the 1-D equivalent linear and non-linear site response analyses. Due to high vulnerability and seismicity of the city center of Kirikkale surrounded by active many faults, such as the North Anatolian Fault (NAF), the city of Kirikkale is classified as highly earthquake-prone city. The first effort to determine critical site response parameter is to perform the seismic hazard analyses of the region through the earthquake record catalogues. The moment magnitude of the city center is obtained as $M_w=7.0$ according to the recorded probability of exceedance of 10% in the last 50 years. Using the data from site tests, the 1-D equivalent linear (EL) and nonlinear site response analyses (NL) are performed with respect to the shear modulus reduction and damping ratio models proposed in literature. The important engineering parameters of the amplification ratio, predominant site period, peak ground acceleration (PGA) and spectral acceleration values are predicted. Except for the periods between the period of T=0.2-1.0 s, the results from the NL are obtained to be similar to the EL results. Lower spectral acceleration values are estimated in the locations of the city where the higher amplification ratio is attained or vice-versa. Construction of high-rise buildings with modal periods higher than T=1.0 s are obtained to be suitable for the city of Kirikkale. The buildings at the city center are recommended to be assessed with street survey rapid structural evaluation methods so as to mitigate seismic damages. The obtained contour maps in this study are estimated to be effective for visually characterizing the city in terms of the considered parameters.

• 지질공학
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• 제17권4호
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• pp.545-554
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• 2007

자연사면 산사태는 주요 유발인자인 강우나 지진 이외에 토질특성, 지형 및 지질요소 등 다양한 인자의 영향으로 발생될 수 있다. 본 연구지역의 경우 파괴의 시점에 인공구조물이 시공되어 있어 이들과 사면붕괴와의 관련성을 밝히는 것은 매우 의미가 있다. 이를 위해 원지반의 물성을 추정하여 자연사면 자체의 붕괴에 대한 취약성을 파악하고 구조물에 의해 변화된 지반에 대한 불안정성을 비교하여 붕괴원인을 살펴보았다. 현장조사와 실내시험으로 원지반과 성토지반의 물성을 구하였고, 지구물리탐사를 통해 추정된 파괴면의 심도를 이용하여 지하수위 변화에 따른 2차원과 3차원 한계평형해석을 각각 수행하였다. 해석결과는 지반의 토질특성과 강도정수에 상관없이 비슷한 안전율을 보였고, 지하수위는 만수위시 불안정해지는 것으로 나타났다.

• Computers and Concrete
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• 제16권4호
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• pp.503-529
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• 2015

Traditionally, multi-story buildings are designed to provide stiffer structural support to withstand lateral earthquake loading. Introducing flexible elements at the base of a structure and providing sufficient damping is an alternative way to mitigate seismic hazards. These features can be achieved with a device known as an isolator. This paper covers the design of base isolators for multi-story buildings in medium-risk seismicity regions and evaluates the structural responses of such isolators. The well-known tower building for police personnel built in Dhaka, Bangladesh by the Public Works Department (PWD) has been used as a case study to justify the viability of incorporating base isolators. The objective of this research was to establish a simplified model of the building that can be effectively used for dynamic analysis, to evaluate the structural status, and to suggest an alternative option to handle the lateral seismic load. A finite element model was incorporated to understand the structural responses. Rubber-steel bearing (RSB) isolators such as Lead rubber bearing (LRB) and high damping rubber bearing (HDRB) were used in the model to insert an isolator link element in the structural base. The nonlinearities of rubber-steel bearings were considered in detail. Linear static, linear dynamic, and nonlinear dynamic analyses were performed for both fixed-based (FB) and base isolated (BI) buildings considering the earthquake accelerograms, histories, and response spectra of the geological sites. Both the time-domain and frequency-domain approaches were used for dynamic solutions. The results indicated that for existing multi-story buildings, RSB diminishes the muscular amount of structural response compared to conventional non-isolated structures. The device also allows for higher horizontal displacement and greater structural flexibility. The suggested isolation technique is able to mitigate the structural hazard under even strong earthquake vulnerability.

• 대한건축학회논문집:구조계
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• 제35권4호
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• pp.135-146
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• 2019

Deep beam has high section modules compared with shallow beam of the same weight. However, deep beam has low rotational capacity and high possibility of brittle failure so it is not possible to apply deep beams with a long span to intermediate moment frames, which should exhibit a ductility of 0.02rad of a story drift angle of steel moment frames. Accordingly, KBC and AISC limit the beam depth for intermediate and special moment frame to 750mm and 920mm respectively. The purpose of this paper is to improve the seismic performance of intermediate moment frame with 1200mm depth beam. In order to enhance vulnerability of plastic deformation capacity of deeper beam, Multi-Reduced Taper Beam(MRTB) shape that thickness of beam flange is reinforced and at the same time some part of the beam flange width is weakened are proposed. Based on concept of multiple plastic hinge, MRTB is intended to satisfy the rotation requirement for intermediate moment frame by dividing total story drift into each hinge and to prevent the collapse of the main members by inducing local buckling and fracture at the plastic hinge location far away from connection. The seismic performance of MRTB is evaluated by cyclic load test with conventional connections type WUF-W, RBS and Haunch. Some of the proposed MRTB connection satisfies connection requirements for intermediate moment frame and shows improved the seismic performance compared to conventional connections.