• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.160-165
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• 1996

The tensile of concrete in one of important factor for study of reinforced concrete as well as prestressed concrete structures. In many countries, a numerous experimental studies are being undertaken to investigate correlation between compressive and tensile strength of concrete. This study is focused on identifying the relationship between the compressive strength and torsional tensile strength of concrete and, on crack of RC and PC structure.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.255-258
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• 2005

The current ACI design code does not take into account the contribution of concrete for the torsional moment of reinforced concrete(RC) beams subjected to pure torsion. This code is not capable of evaluating the inter-effects between concrete and torsional reinforcement on the torsional resistance of the RC beams. In this study, 9 RC beams subjected to pure torsion were tested. The main parameter of the beams was the amount of torsional reinforcement and the angle of twist. Test results indicated that the current ACI code over-estimated the torsional strength of RC beams that had larger amount of torsional reinforcement.

• 한국소음진동공학회논문집
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• 제17권7호
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• pp.572-578
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• 2007

Two stroke low speed diesel engines are widely used for marine propulsion or as power plant prime mover. These engines have many merits which includes higher thermal efficiency, mobility and durability. Yet various annoying vibrations occur sometimes in ships or at the plant itself. Of these vibrations, torsional vibration is very important and dictates a careful investigation during the engme's initial design stage for safe operation. With the rule and limit on torsional vibration in place, shaft strength fatigue due to torsional vibration however demands further analysis which possibly can be incorporated in the classification societies' rule and limit. In addition, the shaft's torsional vibration stresses can be calculated equivalently from accumulated fatigue cycles number due to transient torsional vibration in time domain. In this paper, authors suggest a new estimation method combined with Palmgren-Miner equation. A 6S70MC-C ($25,320ps{\times}91rpm$) engine for ship propulsion was selected as a case study. Angular velocity was measured, instead of shaft's strain, for simplified measurement and it was converted to torsional vibration stress for accumulated fatigue cycle numbers in shafting life time. Likewise, the accumulated fatigue calculation was compared with shaft fatigue strength limit. This new method can be further realized and confirmed in ship with two stroke low speed diesel engine.

• 대한조선학회논문집
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• 제58권6호
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• pp.431-439
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• 2021

The Carbon Fiber Reinforced Plastic (CFRP) material is recently widely used in the composite industry with excellent rigidity and lightweight properties. A ship shaft system requires high standards of safety on torsional strength capacity. The purpose of this study is to verify the applicability of a CFRP shaft system to take the place of metal shaft systems for ships from a viewpoint of torsional strength. Selection of materials and manufacturing method are executed then two geometrically scaled CFRP shaft system models were designed and manufactured with three-layer patterns. The models were used for a series of torsion tests under single and repeated torsional loading conditions. Detailed design and manufacturing methods for a CFRP ship shaft system are documented and the torsion test results are listed in this paper. The results of this study could be useful guidelines on the development of CFRP ship shaft systems and a test method.

• Computers and Concrete
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• 제9권6호
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• pp.469-486
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• 2012

This paper presents Neuro-Fuzzy (NF) based empirical modelling of torsional strength of RC beams for the first time in literature. The proposed model is based on fuzzy rules. The experimental database used for NF modelling is collected from the literature consisting of 76 RC beam tests. The input variables in the developed rule based on NF model are cross-sectional area of beams, dimensions of closed stirrups, spacing of stirrups, cross-sectional area of one-leg of closed stirrup, yield strength of stirrup and longitudinal reinforcement, steel ratio of stirrups, steel ratio of longitudinal reinforcement and concrete compressive strength. According to the selected variables, the formulated NFs were trained by using 60 of the 76 sample beams. Then, the method was tested with the other 16 sample beams. The accuracy rates were found to be about 96% for total set. The performance of accuracy of proposed NF model is furthermore compared with existing design codes by using the same database and found to be by far more accurate. The use of NF provided an alternative way for estimating the torsional strength of RC beams. The outcomes of this study are quite satisfactory which may serve NF approach to be widely used in further applications in the field of reinforced concrete structures.

• Steel and Composite Structures
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• 제9권4호
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• pp.367-380
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• 2009

This study focuses on the experimental evaluation of the flexural-torsional performance of high strength thin-walled composite members. A series of tests on composite members with various sectional aspect ratios subjected to eccentric cyclic loads were conducted. Test results show that the composite member's torsional strength could be approximated using a series of linear segments and evaluated using the superposition of the component steel and reinforced concrete responses. It is also validated from the tests that the strength deterioration of members subjected to combined loads is closely related to the aspect ratios of the sections. An interaction expression between the bending and torsion for high strength thin-walled composite members is proposed for engineering practice references.

• 한국강구조학회 논문집
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• 제19권5호
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• pp.463-472
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• 2007

본 연구에서는 균일한 휨모멘트가 작용하는 파형강판 복부판 I-거더의 횡-비틂 좌굴강도에 관하여 이론적 접근 및 유한요소해석을 이용하여 연구를 수행하였다. 횡-비틂 좌굴 강도는 박판 구조를 갖는 I-단면의 휨부재를 설계 하는데 중요한 인자이다. 하지만 파형강판 복부판 I-거더의 뒴비틀림 상수와 같은 비틀림 거동에 대한 이해가 현재까지는 부족한 실정이며, 이에 대한 연구가 필요하다. 본 연구에서는 휨 및 순수 비틀림 상수를 기존 연구자들의 결과를 이용하여 요약하였으며, 그 후 파형강판 복부판 I-거더 단면의 전단 중심의 위치와 뒴비틀림 상수를 유도하였다. 이러한 단면 상수들을 이용하여 파형강판 복부판 I-거더의 횡-비틂 좌굴 강도를 결정하였으며, 유한요소해석을 수행하여 제안된 파형강판 복부판 I-거더의 횡-비틂 좌굴 강도를 검증하였다. 마지막으로 파형강판의 기하학적 제원이 횡-비틂 좌굴강도에 미치는 영향에 관하여 연구를 수행하였다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
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• pp.314-321
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• 2000

Excessive torsional behavior of asymmetric building structures is observed to be the main cause of the poor seismic performance. Concepts of current design provisions for torsion are based on the assumption that the strength of the lateral load resisting elements can be adjusted without changing their stiffness. This paper investigates inelastic torsional effects of multi-story high rise residential building in Korea on increase of strength demand and ductility of members using some methods published in literature. The methods analyze the reduction of strength and member ductility resulting from torsional mechanisms. This study shows that use of these concepts control inelastic torsion during preliminary seismic design of multi-story building of irregular plans.

• Computers and Concrete
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• 제15권6호
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• pp.935-950
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• 2015

The aim of this study is to provide experimental data regarding the compressive, shear and torsional strength of self-compacting concrete (SCC) used in rectangular beams, and then comparing the results with the equations presented by the CSA A23.3-04 and ACI 318-11. In fact, the gathered information in this field is quite useful for calibrating the computer models of other researchers. The other goal of this study was to investigate the effects of silica fume and superplasticizer dosages on the mechanical properties of SCC. In this research, SCC is made based on 16 different type mixing layout. Also two normal concrete (NC) or vibrating concrete are constructed to compare the results of SCC and NC. This work concentrated on concrete mixes having water/binder ratios of 0.45 and 0.35, which contained constant total binder contents of $400kg/m^3$ and $500kg/m^3$, respectively. The percentages of silica fume that replaced cement were 0% and 10%. The superplasticizer dosages utilized in the mixtures were 0.4%, 0.8%, 1.2% and 1.6% of the weight of cement. Beam dimensions used in this test were $30{\times}30{\times}120cm^3$. The results of this research indicated that shear and torsional strength of SCC beams to be used in computer models can be calculated utilizing the equations presented in CSA A23.3-04 and ACI 318-11.

• Structural Engineering and Mechanics
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• 제55권5호
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• pp.953-964
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• 2015

A model has been proposed that can predict the ultimate torsional strength of single-box multi-cell reinforced concrete box girder under combined loading of bending, shear and torsion. Compared with the single-cell box girder, this model takes the influence of inner webs on the distribution of shear flow into account. According to the softening truss theory and thin walled tube theory, a failure criterion is presented and a ultimate torsional strength calculating procedure is established for single-box multi-cell reinforced concrete box girder under combined actions, which considers the effect of tensile stress among the concrete cracks, Mohr stress compatibility and the softened constitutive law of concrete. In this paper the computer program is also compiled to speed up the calculation. The model has been validated by comparing the predicted and experimental members loaded under torsion combined with different ratios of bending and shear. The theoretical torsional strength was in good agreement with the experimental results.