• Structural Engineering and Mechanics
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• 제9권4호
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• pp.323-338
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• 2000

An analytical approach for the prediction of the behaviour of steel-fiber reinforced concrete beams subjected to torsion is described. The analysis method employs a special stress-strain model with a non-linear post cracking branch for the material behaviour in tension. Predictions of this model for the behaviour of steel-fiber concrete in direct tension are also presented and compared with results from tests conducted for this reason. Further in this work, the validation of the proposed torsional analysis by providing comparisons between experimental curves and analytical predictions, is attempted. For this purpose a series of 10 steel-fiber concrete beams with various cross-sections and steel-fiber volume fractions tested in pure torsion, are reported here. Furthermore, experimental information compiled from works around the world are also used in an attempt to establish the validity of the described approach based on test results of a broad range of studies. From these comparisons it is demonstrated that the proposed analysis describes well the behaviour of steel-fiber concrete in pure torsion even in the case of elements with non-rectangular cross-sections.

• 한국지반공학회지:지반
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• 제4권1호
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• pp.17-28
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• 1988

흙의 역학적거동을 파악하기 위한 요소시험중 공시체의 주응력방향을 회전시킬 수 있는 비틀림 전단시험기의 기능에 대하여 검토하였다. 본 연구에서는 이 비틀림전단시험기가 점토시료에 사용 될 수 있게 개량제작되었다. 이 시험기를 사용하여 반죽성형된 Ko-견밀점토시료에 대한 약간의 비배수 비틀림전단시험을 실시하여 혼의 거동에 미치는 주수력축의 회전영향이 조사되었다. 우선, torque없이 비틀림전단시험기를 사용하여 얻은 흙의 역학적 거동이 통상의 축대칭삼축압 축시험에 의한 결과와 비교검토됐다. 흙의 응력일변형거동, 문극수압및 주응력비는연직하중과 torque에 의한 응력경로에 크게 영향을 받았으며 전단변형률의 증가에 따라 주응력회전각과 주응력의 상대적 크기, b(=o2-o3)/(o1-o3)) 값토 점진적으로 커져 파괴시의 값에 수렴하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.435-438
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• 2008

High temperature deformation of Ti-6Al-4V alloy with a lamellar colony microstructure was investigated by hot compression and torsion tests. The torsion and compression tests were carried out under a wide range of temperatures and strain rates with true strain up to 2 and 0.7, respectively. The processing maps were generated on the basis of compression and torsion test data and using the principles of dynamic materials modeling (DMM). The shapes of the strain-stress curves in alpha-beta region and processing maps obtained on the two different tests have been compared with a view to evaluate the effect of the microstructure evolution on the flow softening behavior of Ti-6Al-4V alloy with a lamellar colony microstructure.

• Computers and Concrete
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• 제1권3호
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• pp.261-284
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• 2004

Two enhancements to a recently developed plastic-damage-contact model for concrete are presented. The model itself, which uses planes of degradation that can undergo damage and separation but that can regain contact according to a contact law, is described. The first enhancement is a new damage evolution function which provides a completely smooth transition from the undamaged to the damaged state and from pre-peak to post-peak regions. The second is an improved contact function that governs the potential degree of contact with increasing opening on a crack plane. The use of a damage evolution function with a pre-peak has implications for the consistent tangent matrix/stress recovery algorithm developed for the model implementation, and amendments to this algorithm to accommodate the new function are described. A series of unpublished experimental tests on notched specimens undertaken in Cardiff in the mid 1990s are then described. These include notched beam tests as well as prismatic and cylindrical torsion tests. The tests are then considered in three dimensional finite element analyses using the modified Craft model implemented in the finite element program LUSAS. Comparisons between experimental and numerical data show reasonable agreement except that the numerical simulations do not fully describe the latter stages of the softening responses for the torsion examples. Finally, it is concluded that the torsion tests described provide useful benchmark examples for the validation of three-dimensional numerical models for concrete.

• 대한치과교정학회지
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• 제22권3호
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• pp.591-602
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• 1992

The purpose of this study was to evaluate the effect of heat treatment on physical properties of 0.016' and 0.016' x 0.022' stainless steel wires. Temperature of heat treatment had intervals of $50^{\circ}C$ from $400^{\circ}C$ to $700^{\circ}C$, and time of heat treatment were 3, 6 and 9 minutes. Tensile tests were measured by ultimate tensile strength and yield strength. Bending tests were assessed by maximum bending force, recovery force, and stiffness. Torsion test was evaluated by torsion cycle until wires were fractured. The results were as follows: 1. In round wires, the highest value of ultimate tensile strength and yield strength were recorded of heat treatment at $500^{\circ}C$. In rectangular wires, the highest value of ultimate tensile strength were after 9 minutes at $400^{\circ}C,\;450^{\circ}C$ and 3, 6 minutes of heat treatment at $50^{\circ}C$, yield strength were the highest value after 3, 6 minutes of heat treatment at $500^{\circ}C$. 2. In both round and rectangular wires, maximum bending force and recovery force were the highest values after 6 minutes of heat treatment at $500^{\circ}C$. In round wires, highest value of stiffness were formed after 9 minutes at heat treatment at $500^{\circ}C$. In rectangular wires, the highest value of stiffness were for 6 minutes in $500^{\circ}C$. 3. In rectangular wires, torsion cycle was minimum after 6 minutes of heat treatment at $500^{\circ}C$. 4. In all of tension, bending, and torsion tests, the heat treated wires were softened over at $700^{\circ}C$. 5. In all of tension, bending, and torsion tests, physical properties of the wires were more influenced by the temperatures than the duration of the heat treatment.

• 대한토목학회논문집
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• 제8권1호
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• pp.151-157
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• 1988

$K_0$-압밀점토(壓密粘土)의 응력(應力)-변형거동(變形擧動) 및 강도특성(强度特性)에 미치는 주응력회전(主應力回轉)의 영향을 조사하기 위하여 중공원통형공시체(中空圓筒型供試體)에 대하여 응력경로(應力徑路)를 여러가지로 변경시키면서 비틀림전단시험(剪斷試驗)을 실시하였다. 본(本) 연구(硏究) 결과로부터 응력경로(應力徑路) 및 주응력회전(主應力回轉)은 주로 파괴(破壞) 이전의 응력(應力)-변형거동(變形擧動)에 영향을 미치고 있음을 알 수 있었다. 또한, 비틀림전단시험(剪斷試驗) 결과로부터 얻어진 파괴강도(破壞强度)는 등방체(等方體)에 제안된 파괴규준(破壞規準)(failure criterion)과 실용적으로 잘 일치하였으며, 전단응력(剪斷應力)과 연직응력(鉛直應力)이 함께 작용될 때 응력(應力)과 변형율(變形率) 사이에 결합효과(結合効果)(coupling effect)가 발생하였다. 마지막으로 비틀림전단시험(剪斷試驗) 결과에 대한 일공간(空間)(work space)개념이 설명되고 응력(應力)과 변형율증분(變形率增分) 사이의 관계가 이 일공간(空間) 상에서 검토되었다.

• Asian Pacific Journal of Cancer Prevention
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• 제17권11호
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• pp.4981-4984
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• 2016

Background: Adnexal torsion results in ischemia of structures distal to twisted pedicle and acute onset of pain is responsible for about 3% of all gynecologic emergencies. Ovarian torsion classically occurs in a pathological enlarged ovary, as with cancer, but diagnosis remains a challenge. Objective: Our purpose was to evaluate clinical risk factors predictive of torsion with gangrenous adnexa. Material and methods: A retrospective descriptive study and chart review of surgically proven ovarian torsion/adnexal torsion cases at the Obstetrics and Gynecology Department of Prapokklao Hospital, Chanthaburi, Thailand between January 2011 and December 2015 was conducted. Result: Seventy-eight cases were identified. Mean age at presentation was 35.5 years. The average maximum diameter of the ovarian tumors was 10.8 cm. The percentage of gangrenous ovarian cysts in this study was 46.2 (36/78). The precision to determine the pathological site by patient, physician and ultrasonography was 8.5, 24.2 and 83.3 percent, respectively with statistically significant variation. Conclusion: Ovarian/adnexal torsion remains a challenge condition especially in young nulliparous women. Sophisticated investigation does not guarantee ovary preservation. Combining clinical acumen, appropriate tests and detailed consideration may be the best practice at the present time.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제12권4호
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• pp.275-287
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• 2005

Geometric invariants are basic tools for geometric processing and computer vision. In this paper, we give a linear approximation for the differentiation of the binormal vector field of a space curve by using the forward and backward differences of discrete binormal vectors. Two kind of discrete torsion, say, back-ward torsion $T_b$ and forward torsion $T_f$ can be defined by the dot product of the (backward and forward) discrete differentiation of binormal vectors that are linear approximations of torsion. Using Frenet formula and Taylor series expansion, we give error estimations for the discrete torsions. We also give numerical tests for a curve. Notably the average of $T_b$ and $T_f$ looks more stable in errors.

• Structural Engineering and Mechanics
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• 제23권6호
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• pp.713-737
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• 2006

This paper presents the results of an experimental investigation on the behaviour of 56 reinforced concrete beams subjected to pure torsion. The reported results include the behaviour curves, the failure modes and the values of the pre-cracking torsional stiffness, the cracking and ultimate torsional moments and the corresponding twists. The influence of the volume of stirrups, the height to width ratios and the arrangement of longitudinal bars on the torsional behaviour is discussed. In order to describe the entire torsional behaviour of the tested beams, the combination of two different analytical models is used. The prediction of the elastic till the first cracking part is achieved using a smeared crack analysis for plain concrete in torsion, whereas for the description of the post-cracking response the softened truss model is used. A simple modification to the softened truss model to include the effect of confinement is also attempted. Calculated torsional behaviour of the tested beams and 21 beams available in the literature are compared with the experimental ones and a very good agreement is observed.

• Earthquakes and Structures
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• 제19권1호
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• pp.59-77
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• 2020

The code static eccentricity model for elastic torsional design of structures has two critical shortcomings: (1) the negation of the inertial torsional moment at the center of mass (CM), particularly for torsionally-unbalanced (TU) building structures, and (2) the confusion caused by the discrepancy in the definition of the design eccentricity in codes and the resistance eccentricity commonly used by engineers such as in FEMA454. To overcome these shortcomings, using the resistance eccentricity model that can accommodate the inertial torsional moment at the CM, interactive relations between shear and torsion are proposed as follows: (1) elastic responses of structures at instants of peak edge-frame drifts are given as functions of resistance eccentricity, and (2) elastic hysteretic relationships between shear and torsion in forces and deformations are bounded by ellipsoids constructed using two adjacent dominant modes. Comparison of demands estimated using these two interactive relations with those from shake-table tests of two TU building structures (a 1:5-scale five-story reinforced concrete (RC) building model and a 1:12-scale 17-story RC building model) under the service level earthquake (SLE) show that these relations match experimental results of models reasonably well. Concepts proposed in this study enable engineers to not only visualize the overall picture of torsional behavior including the relationship between shear and torsion with the range of forces and deformations, but also pinpoint easily the information about critical responses of structures such as the maximum edge-frame drifts and the corresponding shear force and torsion moment with the eccentricity.