• Title/Summary/Keyword: Ductile shear zone

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On the Properties and Intersection Feature of the Ductile Shear Zone (Chonju shear zone) near Yongkwang-Eub (영광(靈光) 부근(附近) 연성전단대(延性剪斷帶)(전주전단대(全州剪斷帶))의 성질(性質)과 교차양상(交叉樣相)에 관(關)하여)

  • Jeon, Kyeong Seok;Chang, Tae Woo;Lee, Byung Joo
    • Economic and Environmental Geology
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    • v.24 no.4
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    • pp.435-446
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    • 1991
  • Ductile shear zones developed in Jurassic granites in the Yonggwang area show NE trend at the eastern part and nearly EW trend at the western part, respectively. Judged from shear sense indicators, they have resulted from dextral strike-slip movement. The intersection of both trends is thought to be due to the truncation and offset of NE shear zone Chonju Shear zone by the brittle Yonggwang fault which runs in near EW direction with sinistral movement sense. The simple shear deformation was predominate through the deformation in this ductile shear zone. Based on this deformation mechanism, the shear strain (${\gamma}$) estimated in domain 1 increases from 0.14 at the shear zone margin to 9.41 toward the center of shear zone. Total displacement obtained only from this measured section(JK 59 to JK14) appecars to be 1434.5 meters. The sequential development of microstructures can be divided into three stages; weakly-foliated, well-foliated and banded-foliated stages. In the weakly-foliated stage dislocation glide mechanism might be predominant. In the well-foliated stage grain boundary migration and progressive misorientation of subgrains was remarkable during dynamic recovery and recrystallization. In the banded-foliated stage grain boundary sliding and microfracturing mechanisms accompanied with crushing and cracking were marked. According to strain analysis from quartzites of the metasedimentary rocks, strain intensity (${\gamma}$) of the samples within the ductile shear zone ranges from 2.7 to 5.7, while that of the samples out of the ductile shear zone appears to be about 1.7.

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Impact of shear wall design on performance and cost of RC buildings in moderate seismic regions

  • Mahmoud, Sayed;Salman, Alaa
    • Earthquakes and Structures
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    • v.21 no.5
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    • pp.489-503
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    • 2021
  • This research aims to investigate the seismic response of RC shear wall buildings of 5-, 6-, 7-, 8-, 9-, and 10-story designed as conventional and ductile and located in moderate seismic zone in Saudi Arabia in accordance with the seismic provisions of the American code ASCE-7-16. Dynamic analysis is conducted using the developed models in ETABS and the design spectra of the selected zone. The seismic responses of a number of design variations are evaluated in terms of story displacements, drift, shear and moments of both conventional and ductile building models as performance measures and presented comparatively. In addition, pushover analysis is also performed for the lowest and highest building models. Cost estimate of ductile and conventional walls is evaluated and compared to each other in terms of weight of reinforcement bars. In addition, due to the complexity of design and installation of ductile shear walls, sensitivity analysis is performed as well. It is observed that conventional design considerably increases induced seismic responses as well as cost compared to ductile one.

Ductile Shear Deformation around Jirisan Area, Korea (지리산 일대의 연성전단변형)

  • Ryoo, Chung-Ryul;Kang, Hee-Cheol;Lee, Sang-Won
    • The Journal of the Petrological Society of Korea
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    • v.28 no.2
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    • pp.53-69
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    • 2019
  • In the Jirisan area of the Yeongnam Massif, Korea, several ductile shear zones are developed within Precambrian gneiss complex (Jirisan metamorphic rock complex). The ductile shear zones have a general NS- and NNE-striking foliation with westward dipping directions. The foliation developed in the shear zones cut the foliation in gneiss complex. The stretching lineations are well developed in the foliated plane of the shear zone, showing ENE-trend with gentle plunging angle to the ESE direction. Within shear zone, several millimetric to centimetric size of porphyroclasts are deformed strongly as a sigmoid form by ductile shearing. The sigmoid patterns of porphyroclasts in the shear zones indicate the dextral shearing. The spatial distribution of ductile shear zone is characterized by the dominant NS- and NNE-striking dextral sense in the central and eastern regions respectively. In the western part, it develops in NE-striking dextral sense which is the general direction of the Honam shear zone. The U-Pb concordant ages obtained from the two samples, the strongly sheared leucocratic gneiss, are $1,868{\pm}3.8Ma$ and $1,867{\pm}4.0Ma$, respectively, which are consistent with the U-Pb ages reported around the study area. We supposed that the ductile shearing in the study area is occurred about 230~220 Ma during late stage of the continental collision around Korea and is preceded by granitic intrusion related to subduction during 260~230 Ma, which are supported by compiling the age data from sheared gneiss, deformed mafic dyke intruded gneiss complex, and non-deformed igneous rocks.

The temperature condition for the mylonitization of the Cheongsan granite, Korea (변형된 청산 화강암의 압쇄암화작용시의 변형온도 - 변형된 청산 화강암의 구조 해석 -)

Shear Deterioration of Reinforced Concrete Beams Failing in Shear after Flexural Yielding (휨항복 후 전단 파괴하는 철근콘크리트 보의 전단성능 저하에 관한 연구)

  • 이정윤
    • Journal of the Korea Concrete Institute
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    • v.13 no.5
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    • pp.466-475
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    • 2001
  • The potential shear strength of reinforced concrete beams decreases after flexural yielding due to the decrease of the effective compressive strength of concrete in plastic hinge zone. A truss model considering shear deterioration in the plastic hinge zone was proposed in order to evaluate the ductile capacity of reinforced concrete beams failing in shear after flexural yielding This model can determine the potential shear strength of the beam by using a truss model. The potential shear strength gradually decreases as the increase of the axial strain of member. When the calculated potential shear strength decreases up to the flexural yielding strength, the corresponding rotation angle is defined as the ductile capacity of the beam. The predicted ductile capacity of reinforced concrete beams is shown to be in a good agreement with experimental results.

Structural characteristics of the Yecheon Shear Zone in the Pukhumyeon-Pyeongeunmyeon area, Gyeongsangbukdo, Korea (경상북도 북후면-평은면 지역에 발달된 예천전단대의 구조적 특성)

Geological Structures of the Imgye Area, Kangweondo, Korea (강원도(江原道) 임계지역(臨溪地域)의 지질구조(地質構造))

  • Kim, Jeong Hwan;Kee, Weon Seo
    • Economic and Environmental Geology
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    • v.24 no.1
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    • pp.43-55
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    • 1991
  • The Imgye area, in the NE Taebaegsan Region, consists of Precambrian granites and schist complex at the base and Paleozoic sedimentary rocks and amphibolite at cover. The granites in the area were previously thought to be Paleozoic in age, but recent geochronological data yields isotopic age ranging from $1837{\pm}82Ma$ to $2108{\pm}82Ma$ by Rb-Sr whole rock method. Therefore, basement-cover relations in the area should be reexamined. During the study, mylonite zone recognized along the contact boundary between Precambrian granites and Cambrian Jangsan Quartzite Formation. Mylonite zone has 150 - 250 m in width. Mylonitic rocks can divide into two groups; quartz mylonite derived from Jangsan Formation and mylonitic granites from Precambrian granites. Intensity of mylonitic foliation decreased toward the north. Amphibolite occurs as an intrusive sills within mylonite zone. Mineral fabrics and small scale shear zones are commonly seen in amphibolite. It indicates that intrusive age of amphibolite is synchronous to the formation of mylonite zone. Mylonite zone was reactivated as ductile thrust faults and forms the hinterland dipping imbricate zone during the Cretaceous Bulkuksa Orogeny. The near parallelism of mineral stretching lineation and long axis of strain ellipes indicates that the area is affected by a homogeneous pure shear flattening together with the variable components of simple shear.

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CHIME Monazite Ages of Jurassic Foliated Granites in the Vicinity of the Gangjin Area, Korea (강진 인근 쥬라기 엽리상 화강암류의 CHIME 모나자이트 연대측정)

  • Cho, Deung-Lyong;Kee, Weon-Seo;Suzuki, Kazuhiro
    • The Journal of the Petrological Society of Korea
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    • v.16 no.3
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    • pp.101-115
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    • 2007
  • The CHIME (chemical Th-U-total Pb isochron method) dating on monazite was carried out for two foliated granites from a dextral ductile shear zone in the vicinity of Gangjin area, which is considered to be a southern extension of Sunchang shear zone. The result gives emplacement age of the medium-grained biotite granite and the coarse-grained biotite granite as $183.6{\pm}2.2Ma$(MSWD=0.21) and $171.7{\pm}4.0Ma$(MSWD=0.57), respectively. Microtextures of quartz and feldspar observed in the foliated granite are almost identical with those reported in Jurassic (ca 180 Ma) foliated granites from the Imsil-Namwon area of the Sunchang shear zone, and they constraint that the ductile deformation took place at temperature condition of $300{\sim}550^{\circ}C$. Assuming cooling curves of the foliated granites in this study are similar with those of Jurassic foliated granites from Imsil-Namwon area, dextral ductile shear in the Gangjin area would take place between 172 Ma and 150 Ma, about 10 Ma later than the previous estimation based on CHIME monazite ages.

Engineering Properties of Mylonite in the Youngju Area (영주지역 압쇄암의 공학적 특성 연구)

  • Kim, Sung-Wook;Choi, Eun-Kyeong;Yang, Tae-Sun;Lee, Kyu-Hwan
    • Journal of the Korean Geotechnical Society
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    • v.27 no.10
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    • pp.35-43
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    • 2011
  • The area to be studied is the place where the main line rail way will be constructed in accordance with the scheduled construction project of Yeongju dam, and is a fold and mylonite zone over several km that is formed by ductile-shearing effect. The ductile shear zone, which has been transformed by faulting for long geological time, shows a complicated geological structure. Due to the recrystallization of mineral caused by transformation in deep underground (>8km), a mylonite zone with lamellar structure has properties distinguished from other fault zones formed by transformation near earth surface <2km). To see the properties of mylonite, this study analyzed the transformation rate of sample rocks and the shape of constriction structure accompanied with transformation. While the transformation of fault zone shows a round oblate, the mylonite zone shows a prolate form. Transformation rate in fault zone was measured to be less than 1.2 compared to the state before transformation while the measured rate in mylonite zone was 2.5 at most. Setting the surface of discontinuity as the base, the unconfined compressive strength of slickenside can be categorized in sedimentary rocks, and a change of strength was observed after water soaking over certain time. Taking into account that the weathering resistance of the rock based on mineral and chemical organization is relatively higher, its engineering properties seems to result from the shattered crack structure by crushing effect. When undertaking tunnel construction in mylonite zone, there should be a special care for the expansion of shattered cracks or the fall of strength by influx of ground water.

Ductility Confinement of RC Rectangular Shear Wall (장방형 철근 콘크리트 전단벽의 연성 보강)

  • 강수민;박홍근
    • Journal of the Korea Concrete Institute
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    • v.14 no.4
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    • pp.530-539
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    • 2002
  • In designing the boundary confinement of shear walls, the current design provisions and recommendations are empirical and prescriptive; they specify a certain confinement length and details, regardless of the actual requirement of ductility Therefore, they are inappropriate to the performance based-design. The purpose of the present study is to develop a ductility design method that Is applicable to the performance based-design of shear wall. For the purpose, experimental studies were performed to investigate variations in the ductility of shear walls with the length of the boundary confinement. Five specimens modeling the compressive zone of cross sections with different confinement area were tested against eccentric vertical load. Through the experimental studies, strength, ductility, and failure mode of the compression zone were investigated. In addition, nonlinear numerical analyses for the overall cross-sections of shear wall were performed to investigate variations of the stress and strain profiles with the length of compression zone. On the basis of the experimental and numerical studies, a ductility design method for shear wall was developed. By using the proposed design method, for a given ductility demand, the area of lateral confinement and corresponding reinforcement ratio can be precisely determined so that the ductile behavior and economical design are assured.