• Earthquakes and Structures
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• 제9권1호
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• pp.145-171
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• 2015

Due to earthquakes, many structures suffered extensive damages that were attributed to the torsional effect caused by mass, stiffness or strength eccentricity. Due to this type of asymmetry torsional moments are generated that are imposed by means of additional shear forces developed at the vertical resisting structural elements of the buildings. Although the torsional effect on the response of reinforced concrete buildings was the subject of extensive research over the last decades, a quantitative index measuring the amplification of the shear forces developed at the vertical resisting elements due to lateral-torsional coupling valid for both elastic and elastoplastic response states is still missing. In this study a reliable index capable of assessing the torsional effect is proposed. The performance of the proposed index is evaluated and its correlation with structural response quantities like displacements, interstorey drift, base torque, shear forces and upper diaphragm's rotation is presented. Torsionally stiff, mass eccentric single-story and multistory structures, subjected to bidirectional excitation, are considered and nonlinear dynamic analyses are performed using natural records selected for three hazard levels. It was found that the proposed index provides reliable prediction of the magnitude of torsional effect for all test examples considered.

• 한국전산구조공학회논문집
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• 제26권1호
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• pp.19-28
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• 2013

전단벽-골조 구조시스템의 구조적인 거동은 휨거동하는 전단벽과 전단거동하는 골조의 상호작용에 의하여 결정된다. 이러한 전단벽-골조 구조물의 거동특성을 효과적으로 고려하기 위하여 선행 연구에서는 2차원 T형 강체를 사용한 단순 해석모델을 제안하였다. 본 논문에서는 이를 바탕으로 편심코어를 가진 전단벽-골조 구조물에 대한 효율적인 해석모델을 제안한다. 2차원 등가모델을 3차원으로 확장하여 비틀림 거동을 고려할 수 있도록 하였고, 그 결과 제안하는 등가모델이 편심코어를 가지는 전단벽-골조 구조물에도 적용가능 하도록 하였다.

• Steel and Composite Structures
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• 제20권4호
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• pp.801-812
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• 2016

In an actual design, none of the structures with shear behaviors will be designed for torsional moments. Any failure or damages to roofs, infills, shear walls, and braces caused by an earthquake, will inevitably result in relocation of center of mass and rigidity of the structure. With these changes, the dynamic characteristics of structure could be changed during an earthquake at any moment. The main objective of this paper is to obtain the relationship between time-varying eccentricity of load and corner lateral displacement. In this study, various methods have been used to determine the structural response for time-varying lateral corner displacement. As will be seen below, some of the structural calculation methods result in a significant deviation from the actual results, although these methods include the interaction effects of modes. Controlling the lateral displacement of structure can be performed in different ways such as, passive dampers, friction dampers, semi-active systems including the MR damper and active Systems. Selecting and locating these control systems is very important to bring the maximum safety with minimum cost into the structure. According to this study will be show the relation between the corner lateral displacements of structure and time-varying eccentricity by different kind of methods during an earthquake. This study will show that the response of the structure at the corners due to an earthquake can be very destructive and because of changing the eccentricity of load, calculating the maximum possible response of system can be carried out by this method. Finally, some kind of systems must be used for controlling these displacements. The results shows that, the CQC, DSC and exact methods is comply each other but the results of Vanmark method is not comfortable for these kind of buildings.

• Structural Engineering and Mechanics
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• 제26권4호
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• pp.459-477
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• 2007

A bi-directional tuned mass damper (BTMD) in which a mass connected by two translational springs and two viscous dampers in two orthogonal directions has been introduced to control coupled lateral and torsional vibrations of asymmetric building. An efficient control strategy has been presented in this context to control displacements as well as acceleration responses of asymmetric buildings having asymmetry in both plan and elevation. The building is idealized as a simplified 3D model with two translational and a rotational degrees of freedom for each floor. The principles of rigid body transformation have been incorporated to account for eccentricity between center of mass and center of rigidity. The effective and robust design of BTMD for controlling the vibrations in structures has been presented. The redundancy of optimum design has been checked. Non dominated sorting genetic algorithm (NSGA) has been used for tuning optimum stages and locations of BTMDs and its parameters for control of vibration of seismically excited buildings. The optimal locations have been observed to be reasonably compact and practically implementable.

• Clinics in Shoulder and Elbow
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• 제1권1호
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• pp.78-82
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• 1998

The following will describe a method of evaluating the SLAP lesion in the recurrent anterior dislocation of the shoulder. We have named it the biceps load test. The biceps load test is performed with the patient in the supine position and the arm to be examined is abducted 90/sup°/, and the forearm is in the supinated position. First, the anterior apprehension test is performed. When the patient become apprehensive, the patient is allowed active flexion of the elbow, while the examiner resists elbow flexion. If the apprehension is relieved or diminished, the test is negative. If aggravated or unchanged, the test is positive. A prospective study was performed, in which 75 patients who were diagnosed as having recurrent unilateral anterior instability of the shoulder underwent the biceps load test and arthroscopic examination. The biceps load test showed negative results in 64 of these patients, of which the superior labral-biceps complex was intact'in 63 cases and only I shoulder revealed a type n SLAP lesion. E]even patients with a positive test were confirmed to have type n SLAP lesions. A positive biceps load test represents an unstable SLAP lesion in a patient with recurrent anterior dislocation of the shoulder. The biceps load test is a reliable test for evaluating the SLAP lesion in the recurrent anterior dislocation of the shoulder(sensitivity: ,9] .7%, specificity: 100%, positive predictive value: 1.00 and negative predictive value: 0.98). Biceps contraction increases the torsional rigidity ?of the glenohumeral joint and long head of biceps tendan act as internal rotator of the shoulder in the abducted and externally rotated position. These stabilize the shoulder in abduction and external rotation position in the biceps load test.