• 한국공간구조학회논문집
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• 제17권3호
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• pp.99-105
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• 2017

The SLIM AU composite beam consists of U-shaped steel plate, A-shaped steel cap and infilled concrete. The bottom steel plate acts as tension bars, and the top steel cap takes roles of shear connector and compression bars in the conventional reinforced concrete section. In this paper the shear strength of this composite beam with closed steel section has been evaluated through the concentrated loading shear experiments. Test results under the symmetrical and asymmetrical loading conditions were compared with the predicted values based on the KBC 2016. The composite beam showed the greater shear strength capacities than those of the theoretical evaluation.

• 대한기계학회논문집A
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• 제27권7호
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• pp.1217-1226
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• 2003

The purpose of this paper is to investigate fatigue crack behavior under shear(Mode II) loading. Various specimens and devices have been used in order to produce Mode II loading in fatigue experiments for shear crack propagation. But, there is not sufficient comparisons of experimental results between Mode II and others loading modes, because of characteristics of applied loads and specimens. So, compact tension shear(CTS) specimens were used in this paper to investigate the propagation behavior of Mode II by comparing the experimental results between loading modes. We firstly observed the characteristics which was showed in Mode II experiment using CTS specimens. The experimental results under Mode II loading were compared with fatigue crack behavior under Mode I and Mixed-mode I＋II loading. The characteristics for initiation and propagation behavior under Mode II loading was investigated by such comparisons.

• Geomechanics and Engineering
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• 제14권2호
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• pp.195-202
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• 2018

Many laboratory experiments on crack propagation under uniaxial loading and biaxial loading have been conducted in the past using transparent materials such as resin, polymethyl methacrylate (PMMA), etc. However, propagation behaviors of three-dimensional (3D) cracks in rock or rock-like materials under tri-axial loading are often considerably different. In this study, a series of true tri-axial loading tests on the rock-like material with two semi-ellipse pre-existing cracks were performed in laboratory to investigate the acoustic emission (AE) characteristics and propagation characteristics of 3D crack groups influenced by intermediate principal stress. Compared with previous experiments under uniaxial loading and biaxial loading, the tests under true tri-axial loading showed that shear cracks, anti-wing cracks and secondary cracks were the main failure mechanisms, and the initiation and propagation of tensile cracks were limited. Shear cracks propagated in the direction parallel to pre-existing crack plane. With the increase of intermediate principal stress, the critical stress of crack initiation increased gradually, and secondary shear cracks may no longer coalesce in the rock bridge. Crack aperture decreased with the increase of intermediate principal stress, and the failure is dominated by shear fracturing. There are two stages of fracture development: stable propagation stage and unstable failure stage. The AE events occurred in a zone parallel to pre-existing crack plane, and the AE zone increased gradually with the increase of intermediate principal stress, eventually forming obvious shear rupture planes. This shows that shear cracks initiated and propagated in the pre-existing crack direction, forming a shear rupture plane inside the specimens. The paths of fracturing inside the specimens were observed using the Computerized Tomography (CT) scanning and reconstruction.

• 한국공간구조학회논문집
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• 제23권2호
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• pp.53-60
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• 2023

Recently, a novel cast-in specialty insert was developed in Korea as an anchor for lightweight pipe supports, including fire-protection pipes. As these pipe supports and anchors play a critical role in transferring loads of fire-protection pipes to structural members, it is crucial to evaluate their seismic performance before applying the newly developed insert. In this study, the seismic shear performance of the insert anchors was evaluated through cyclic loading tests based on the loading protocols of ACI 355.2 and FEMA 461. Initially, five monotonic loading tests were conducted on the insert anchors in cracked concrete, followed by cyclic loading tests based on the monotonic test results. The findings revealed that the insert anchors exhibited negligible decrease in shear strength even after cyclic loading. Furthermore, a comparison of the maximum load and displacement of the insert anchors obtained under the loading protocols of ACI 355.2 and FEMA 461 was performed to investigate the applicability of the FEMA 461 loading protocol for anchor performance evaluation.

• Earthquakes and Structures
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• 제5권2호
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• pp.239-259
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• 2013

Typically, beams that form part of structural systems are subjected to vertical distributed loading along their length. Distributed loading affects moment and shear distribution, and consequently spread of inelasticity, along the beam length. However, the finite element models developed so far for seismic analysis of frame structures either ignore the effect of vertical distributed loading on spread of inelasticity or consider it in an approximate manner. In this paper, a beam-type finite element is developed, which is capable of considering accurately the effect of uniform distributed loading on spreading of inelastic deformations along the beam length. The proposed model consists of two gradual spread inelasticity sub-elements accounting explicitly for inelastic flexural and shear response. Following this approach, the effect of distributed loading on spreading of inelastic flexural and shear deformations is properly taken into account. The finite element is implemented in the seismic analysis of plane frame structures with beam members controlled either by flexure or shear. It is shown that to obtain accurate results the influence of distributed beam loading on spreading of inelastic deformations should be taken into account in the inelastic seismic analysis of frame structures.

• Computers and Concrete
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• 제33권5호
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• pp.519-533
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• 2024

Many materials including cementitious concrete-type materials undergo material property changes during high-rate loading. There is a wealth of research regarding this phenomenon for concrete in compression and tension. However, there is minimal knowledge about how mortar material used in concrete masonry unit (CMU) construction behaves in high-rate shear loading. A series of experiments was conducted to examine the bond strength of mortar bonded to CMU units under high-rate shear loading. A novel experimental setup using a shock tube and dynamic ram were used to load specially constructed shear triplets in a double lap shear configuration with no pre-compression. The Finite Element Method was leveraged in conjunction with data from the experimental investigation to establish if the shear bond between concrete masonry units and mortar exhibits any rate dependency. An increase in shear bond strength was observed when loaded at a high strain rate. This data indicates that the CMU-mortar bond exhibits a rate dependent strength change and illustrates the need for further study of the CMU-mortar interface characteristics at high strain rates.

• 터널과지하공간
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• 제9권4호
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• pp.350-363
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• 1999

주기전단하중 하의 암석 절리에 대한 역학적 거동을 규명하기 위해 정밀 주기전단시험 장치를 설계·제작하였다. 실험실에서 황등화강암과 여산대리석 인공 절리 시료로 펑면절리와 거친 절리에 대해 일련의 주기전단시험을 실시하였다. 시료에 대한 레이저 변위계를 이용한 3차원 거칠기 측정을통해 절리의 거칠기 특성을규명하였다. 주기전단시험 결과를 통해 주기전단 과정의 단계별 거동 특성과하중과제하시의 거동 차이, 전단거동의 이방성 등을고찰하였다. 거친 절리면의 역학적 거동 특성은 주로 2차 거칠기의 영향과 암석 재료의 높은 강도에 영향을 받았다. 주기전단시 거친 절리에 대한 돌출부 손상이 지수적인 거칢각 손상 법칙을 따름을 실험적으로 검증하였으며, 수직응력파 거칠기 종류, 하중 단계에 따라 돌출부들의 손상 기구가 다름을 확인하였다.

• Geomechanics and Engineering
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• 제13권5호
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• pp.809-823
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• 2017

This paper describes lab test results of artificial rock-like material samples having a plane joint. Cyclic shear tests were performed under different normal loads and different shear displacement amplitudes. For this purpose, multi-stage normal loading tests (30 kN, 60 kN, 90 kN, 180 kN, 360 kN and 480 kN) with cyclic excitation at frequency of 1.0 Hz and different shear displacement amplitudes (0.5 mm, 1.0 mm, 2.0 mm, 4.0 mm, 5.0 mm, and 8.0 mm) were conducted using the big shear box device GS-1000. Experimental results show, that shear forces increase with the increase of normal forces and quasi-static friction coefficient is larger than dynamic one. With the increase of normal loads, approaching the peak value of shear forces needs larger shear displacements. During each cycle the normal displacements increase and decrease (rotational behavior in every cycle). Peak angle of inclination increases with the increase of normal load. A phase shift between maximum shear displacement and maximum shear force is observed. The corresponding time shift decreases with increasing normal load and increases with increasing shear displacement amplitudes.

• Earthquakes and Structures
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• 제7권5호
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• pp.691-704
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• 2014

Reinforced concrete (RC) shear walls are commonly used for building structures to resist seismic loading. While the RC shear walls can have a high load-carrying capacity, they tend to fail in a brittle mode under shear, accompanied by forming large diagonal cracks and bond splitting between concrete and steel reinforcement. Improving seismic performance of shear walls has remained a challenge for researchers all over the world. Engineered Cementitious Composite (ECC), featuring incredible ductility under tension, can be a promising material to replace concrete in shear walls with improved performance. Currently, the application of ECC to large structures is limited due to the lack of the proper constitutive models especially under shear. In this paper, a new Cyclic Softening Membrane Model for reinforced ECC is proposed. The model was built upon the Cyclic Softening Membrane Model for reinforced concrete by (Hsu and Mo 2010). The model was then implemented in the OpenSees program to perform analysis on several cases of shear walls under seismic loading. The seismic response of reinforced ECC compared with RC shear walls under monotonic and cyclic loading, their difference in pinching effect and energy dissipation capacity were studied. The modeling results revealed that reinforced ECC shear walls can have superior seismic performance to traditional RC shear walls.

• Structural Engineering and Mechanics
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• 제41권1호
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• pp.43-65
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• 2012

The primary objective of this study was to identify concrete contribution to the initial shear strength of reinforced concrete (RC) hollow columns under lateral loading. Seven large-scale RC rectangular hollow column specimens were tested under monotonic or cyclic lateral loads. The most important design parameter was column length-to-depth aspect ratio ranging between 1.5 and 3.0, and the other test variables included web area ratio, hollow section ratio, and loading history. The tests showed that the initial shear strength reduced in a linear pattern as the column aspect ratio increased, and one specimen tested under cyclic loading achieved approximately 83% of the shear strength of the companion specimen under monotonic loading. Also, several pioneering shear models proposed around the world, all of which were mainly based on tests for columns with solid sections, were reviewed and compared with the test results of this study, for their possible applications to columns with hollow sections. After all, an empirical equation was proposed for concrete contribution to the initial shear strength of RC hollow columns based on fundamental mechanics and the test results.