• Earthquakes and Structures
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• 제25권3호
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• pp.177-186
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• 2023

Reinforced concrete frames with a masonry infill panel is a structural typology frequently used worldwide. In seismic cases, the interaction between the masonry infill and the RC frames constitutes one of the most complex subjects in earthquake engineering. In this work, an enhancement of an existing numerical model is proposed to improve the estimation of lateral strength and stiffness of masonry-infilled frame structures and predict their probable failure modes. The proposed improvement is based on attributing corrective coefficients to the shear strength of each diagonal shear spring of the macro element, which simulates the masonry infill. The improved numerical model is validated by comparing the results with those of the original numerical model and with experimental results available in the literature. The enhanced macro element model can be used as a powerful, accessible tool for assessing the capacity and stiffness of masonry-infilled frame structures and predicting their probable failure modes.

• Structural Engineering and Mechanics
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• 제32권2호
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• pp.301-320
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• 2009

Damage assessment for buried structures against an internal blast is conducted by considering the soil-structure interaction. The structural element under analysis is assumed to be rigid-plastic and simply-supported at both ends. Shear failure, bending failure and combined failure modes are included based on five possible transverse velocity profiles. The maximum deflections with respect to shear and bending failure are derived respectively by employing proper failure criteria of the structural element. Pressure-Impulse diagrams to assess damage of the buried structures are subsequently developed. Comparisons have been done to evaluate the influences of the soil-structure interaction and the shear-to-bending strength ratio of the structural element. A case study for a buried reinforced concrete structure has been conducted to show the applicability of the proposed damage assessment method.

• Structural Engineering and Mechanics
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• 제50권1호
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• pp.121-135
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• 2014

Stone masonry structures are widely used around the world, but they deteriorate easily, due to low shear strength capacity. Many techniques have been developed to increase the shear strength of stone masonry constructions. The aim of this experimental study was to investigate the performance of stone masonry walls strengthened by metal connectors as an alternative shear reinforcement technique. For this purpose, three new metal connector (clamp) types were developed. The shear strength of the walls was improved by applying these clamps to stone masonry walls. Ten stone masonry walls were structurally tested in diagonal compression. Various parameters regarding the in-plane behavior of strengthening stone masonry walls, including shear strength, failure modes, maximum drift, ductility, and shear modulus, were investigated. Experimentally obtained shear strengths were confirmed by empirical equations. The results of the study suggest that the new clamps developed for the study effectively increased the levels of shear strength and ductility of masonry constructions.

• Steel and Composite Structures
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• 제20권6호
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• pp.1183-1191
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• 2016

The internal crack propagation, the failure mode and ultimate load bearing capacity of the steel-concrete-steel composite beam under the four-point-bend loading is investigated by the numerical simulation. The results of load - displacement curve and failure mode are in good agreement with experiment. In order to study the failure mechanism, the composite beam has been modeled, which part interface interaction between steel and concrete is considered. The results indicate that there are two failure modes: (a) When the strength of the interface is lower than that of the concrete, failure happens at the interface of steel and concrete; (b) When the strength of the interface is higher than that of the concrete, the failure modes is cohesion failure, i.e., and concrete are stripped because of the shear cracks at concrete edge.

• 한국공간구조학회논문집
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• 제21권2호
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• pp.49-56
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• 2021

The damage to non-structural elements in buildings has been increasing due to earthquakes. In Korea, post-installed anchors produced overseas have been mainly used for seismic anchorage of non-structural components to structures. Recently, a new cast-in-place concrete insert anchor installed in concrete without drilling has been developed in Korea. In this paper, an experimental study was conducted to evaluate the tensile and shear strengths of the newly developed anchor under monotonic load. The failure modes of the tension specimens were divided into concrete breakout failure and steel failure, and all shear specimens showed steel failure. In both tension and shear, the maximum loads of specimens were greater than the nominal strengths predicted by the concrete design code (KDS 14 20 54). As a result, it is expected that the current code can also be used to calculate the strength of the developed cast-in anchor.

• 한국지반공학회논문집
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• 제15권4호
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• pp.207-220
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• 1999

성토지지말뚝으로 지지된 연약지반상 성토지반의 파괴형태를 조사하기 위하여 실내모형실험이 실시되었다. 성토지지말뚝은 성토하중의 지지효과를 증대시키기 위하여 줄말뚝의 형태로 설치하였으며 줄말뚝의 두부는 지중보 형태의 말뚝캡보로 서로 연결시켰다. 이 말뚝캡보는 성토지반의 장축방향에 직각이 되도록 연결시켰다. 사용모래로는 주문진 표준사를 사용하였으며 성토지반의 변형거동을 관찰하기 위하여 흑연가루로 채색한 모래층과 원래의 모래층을 서로 3mm두께로 번갈아 성토하여 줄무늬를 만들었다. 실험중 촬영한 사진분석으로 부터 성토지반의 파괴형태는 지반아칭파괴와 펀칭전단파괴의 두가지임을 알 수 있다. 성토지반내 어떤 파괴형태가 발생될 것인가는 성토고와 말뚝캡보 사이의 간격에 의존함을 알 수 있다. 즉 성토고가 말뚝캡보사이 간격에 비하여 충분히 높으면 지반아칭파괴가 발생되며 그 반대의 경우는 펀칭전단파괴가 발생된다. 지반아칭파괴는 말뚝캡보 폭과 같은 두께를 가지는 반원통형 아치형태로 성토지반내에 발생한다. 그리고, 말뚝캡보 위에는 쐐기영역이 발생하며 이 쐐기영역은 지반아칭파괴나 펀칭전단파괴가 발달하는 동안에도 변형되지 않은 상태로 남아있다. 펀칭전단파괴시 변형토괴의 경계형상도 실험중 촬영한 사진분석에 근거하여 밝혀질 수 있다.

• International Journal of Concrete Structures and Materials
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• 제9권3호
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• pp.267-281
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• 2015

Six full-scale prestressed concrete (PC) I-beams with steel fibers were tested to failure in this work. Beams were cast without any traditional transverse steel reinforcement. The main objective of the study was to determine the effects of two variables-the shear-span-to-depth ratio and steel fiber dosage, on the web-shear and flexural-shear modes of beam failure. The beams were subjected to concentrated vertical loads up to their maximum shear or moment capacity using four hydraulic actuators in load and displacement control mode. During the load tests, vertical deflections and displacements at several critical points on the web in the end zone of the beams were measured. From the load tests, it was observed that the shear capacities of the beams increased significantly due to the addition of steel fibers in concrete. Complete replacement of traditional shear reinforcement with steel fibers also increased the ductility and energy dissipation capacity of the PC I-beams.

• 대한치과기공학회지
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• 제37권4호
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• pp.243-250
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• 2015

Purpose: The aim of this study was to investigate the shear bond strength between various commercial zirconia coping and veneering ceramic, and to observe the failure mode. Methods: For each zirconia block (iJAM Emerald, LUXEN Smile block, ICE Zirkon transluzent), 10 rectangular specimens were layered with Cercon ceram kiss, IPS e.max ceram, ICE Zirkon ceramic according to recommended by the manufacturer. The shear bond strength tests of the veneering porcelain to zirconia were carried out until fracture by a universal testing machine. After the shear bond tests, failure modes were characterized visually, under a stereomicroscope, such as adhesive, cohesive, or mixed. Data were analyzed with One-way ANOVA followed by Scheffe's tests. Results: The shear bond strength ($mean{\pm}SD$) of zirconia-veneer ceramic were JC group $13.9{\pm}3.6MPa$; JE group $17.7{\pm}2.4MPa$; JI group $15.1{\pm}2.5MPa$; LC group $9.5{\pm}1.5MPa$; LE group $16.2{\pm}2.3MPa$; LI group $12.6{\pm}0.8MPa$; ZC group $16.0{\pm}2.3MPa$; ZE group $18.5{\pm}3.4MPa$; and ZI group $15.3{\pm}3.2MPa$. The One-way ANOVA showed a significant difference between groups (p<0.05). The failure mode in most experimental groups was mixed failure, except for the LC group, which showed adhesive failure, and JE group, LE group and ZE group showed cohesive failure. Conclusion: For IPS e.max ceram, the shear bond strength value was highest for all kinds of zirconia blocks. For ICE Zirkon transluzent, the shear bond strength value was highest for all kinds of veneering ceramics. Most of experimental group interfaces revealed mixed failure mode.

• Structural Engineering and Mechanics
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• 제57권4호
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• pp.681-701
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• 2016

This paper presents an experimental study of six steel reinforced high strength concrete T-shaped short-limb shear walls configured with T-shaped steel truss under low cyclic reversed loading. Considering different categories of ratios of wall limb height to thickness, shear/span ratios, axial compression ratios and stirrup reinforcement ratios were selected to investigate the seismic behavior (strength, stiffness, energy dissipation capacity, ductility and deformation characteristics) of all the specimens. Two different failure modes were observed during the tests, including the flexural-shear failure for specimens with large shear/span ratio and the shear-diagonal compressive failure for specimens with small shear/span ratio. On the basis of requirement of Chinese seismic code, the deformation performance for all the specimens could not meet the level of 'three' fortification goals. Recommendations for improving the structural deformation capacity of T-shaped steel reinforced high strength concrete short-limb shear wall were proposed. Based on the experimental observations, the mechanical analysis models for concrete cracking strength and shear strength were derived using the equivalence principle and superposition theory, respectively. As a result, the proposed method in this paper was verified by the test results, and the experimental results agreed well with the proposed model.

• Composites Research
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• 제20권3호
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• pp.17-24
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• 2007

본 연구는 순수 Kevlar 직물과 실리카 입자를 포함하는 전단농화유체가 함유된 Kevlar 액체방탄재(STF-Kevlar)에 대한 방탄충격에 의한 파단모드 연구이다. Cal.22 파편탄과 9mm FMJ 볼탄에 의한 방탄시험에 의하여 이 두 재료는 거시적 측면에서 다른 파단모드를 보여주었다. 순수 Kevlar 직물에서는 얀의 뽑힘(Pull-out)이, 그리고 STF-Kevlar 액체방탄재에서는 얀의 파단이 충격에너지를 흡수하는 주 기구로 나타났다. 전자주사현미경에 의한 미시적 관찰에서 Kevlar 섬유 표면의 벗겨짐, 섬유가 여러 가닥으로 갈라지는 스프리트, 그리고 섬유의 절단, 이 세가지 파단 모드가 손상 정도의 차이는 있지만 공통적으로 두 재료에서 관찰되었다. STF-Kevlar에서, 얀 섬유의 파단은 첫째는 실리카 입자로 덮여있는 얀-얀, 직물-직물 사이의 마찰력과, 둘째는 충격시 전단농화 현상의 발생으로 얀의 이동이 강력하게 억제되기 때문인 것으로 보인다.