• Structural Monitoring and Maintenance
• /
• 제3권4호
• /
• pp.349-375
• /
• 2016

The tension of an arch bridge hanger is estimated using a number of experimentally identified modal frequencies. The hanger is connected through metallic plates to the bridge deck and arch. Two different categories of model classes are considered to simulate the vibrations of the hanger: an analytical model based on the Euler-Bernoulli beam theory, and a high-fidelity finite element (FE) model. A Bayesian parameter estimation and model selection method is used to discriminate between models, select the best model, and estimate the hanger tension and its uncertainty. It is demonstrated that the end plate connections and boundary conditions of the hanger due to the flexibility of the deck/arch significantly affect the estimate of the axial load and its uncertainty. A fixed-end high fidelity FE model of the hanger underestimates the hanger tension by more than 20 compared to a baseline FE model with flexible supports. Simplified beam models can give fairly accurate results, close to the ones obtained from the high fidelity FE model with flexible support conditions, provided that the concept of equivalent length is introduced and/or end rotational springs are included to simulate the flexibility of the hanger ends. The effect of the number of experimentally identified modal frequencies on the estimates of the hanger tension and its uncertainty is investigated.

• Smart Structures and Systems
• /
• 제31권1호
• /
• pp.89-100
• /
• 2023

This paper conducts a parametric study of a new tuned mass damper with pre-strained superelastic SMA helical springs (SMAS-TMD) on the vibration reduction effect. First, a force-displacement relation model of superelastic SMA helical spring is presented based on the multilinear constitutive model of SMA material, and the tension tests of the six SMA springs fabricated are implemented to validate the mechanical model. Then, a dynamic model of a single floor steel frame with the SMAS-TMD damper is set up to simulate the seismic responses of the frame, which are testified by the shaking table tests. The wire diameter, initial coil diameter, number of coils and pre-strain length of SMA springs are extracted to investigate their influences on the seismic response reduction of the frame. The numerical and experimental results show that, under different earthquakes, when the wire diameter, initial coil diameter and number of coils are set to the appropriate values so that the initial elastic stiffness of the SMA spring is between 0.37 and 0.58 times of classic TMD stiffness, the maximum reduction ratios of the proposed damper can reach 40% as the mass ratio is 2.34%. Meanwhile, when the pre-strain length of SMA spring is in a suitable range, the SMAS-TMD damper can also achieve very good vibration reduction performance. The vibration reduction performance of the SMAS-TMD damper is generally equal to or better than that of the classic optimal TMD, and the proposed damper effectively suppresses the detuning phenomena that often occurs in the classic TMD.

• 대한치과교정학회지
• /
• 제11권1호
• /
• pp.17-23
• /
• 1981

This experiment was performed to investigate the response of inorganic substances in alveolar bone in relation to the experimental tooth movement. Right canine in maxillary jaw was tipped in cats by coil springs generating 80 gm. force, in mandibular jaw, the force was 100 gm. force. Cats were divided into five groups and orthodontically treated for one hour, 1, 7, 14 and 28 days, respectively. Alveolar bone samples were obtained from tension and compression sites as well as from contralateral control sites. The level of calcium of alveolar bone was determined by atomic absorption spectrophotometry and inorganic phosphorus was measured by spectrophotometry. The results obtained were as follows: 1. In tension and compression site of maxillary alveolar bone, calcium levels were decreased at 1, 7 and 14 days, but recovered at 28 days. 2. The levels of inorganic phosphorus in compression site of maxillary alveolar bone had little change but in tension site of maxillary alveolar bone , phosphorous levels were decreased, 3. Calcium levels in tension and compression site of mandibular alveolar bone were decreased, especially at 28 days. 4. In tension and compression site of mandibular alveolar bone, inorganic phosphorus were slightly decreased from 1 day.

• 한국정밀공학회지
• /
• 제28권3호
• /
• pp.357-362
• /
• 2011

Air springs are prevalently used as suspension in train. However, air springs are seldom used in automobiles where they improve stability and comfort by enhancing the impact-relief, breaking, and cornering performance. Thus, this study proposed a new method to analyze air springs and obtained some reliable design parameter which can be utilized in vehicle suspension system in contrast to conventional method. Among air spring types of suspension, this study focused on sleeve type of air spring as an analysis model since it has potential for ameliorating the quality of automobiles, specifically in its stability and comfort improvement by decreasing the shock through rubber sleeve. As a methodology, this study used MARC, as a nonlinear finite element analysis program, in order to find out maximum stress and maximum strain depending on reinforcement cord's angle variation in sleeves. The properties were found through uniaxial tension and pure shear test, and they were developed using Ogden Foam which is an input program of MARC. As a result, the internal maximum stresses and deformation according to the changes of cord angle are obtained. Also, the results showed that the Young's modulus becomes smaller, then maximum stresses decrease. It is believed that these studies can be contributed in automobile suspension system.

• Smart Structures and Systems
• /
• 제25권3호
• /
• pp.311-322
• /
• 2020

This paper studies the influence of parameters of a novel SMA helical spring energy dissipation brace on the seismic resistance of a frame structure. The force-displacement relationship of the SMA springs is established mathematically based on a multilinear constitutive model of the SMA material. Four SMA helical springs are fabricated, and the force-displacement relationship curves of the SMA springs are obtained via tension tests. A numerical dynamic model of a two-floor frame with spring energy dissipation braces is constructed and evaluated via vibration table tests. Then, two spring parameters, namely, the ratio of the helical spring diameter to the wire diameter and the pre-stretch length, are selected to investigate their influences on the seismic responses of the frame structure. The simulation results demonstrate that the optimal ratio of the helical spring diameter to the wire diameter can be found to minimize the absolute acceleration and the relative displacement of the frame structure. Meanwhile, if the pre-stretch length is assigned a suitable value, excellent vibration reduction performance can be realized. Compared with the frame structure without braces, the frames with spring braces exhibit highly satisfactory seismic resistance performance under various earthquake waves. However, it is necessary to select an SMA spring with optimal parameters for realizing optimal vibration reduction performance.

• Smart Structures and Systems
• /
• 제25권4호
• /
• pp.393-399
• /
• 2020

In this paper, the design method and experimental validation for the two-degree-of-freedom (2DOF) electromagnetic energy harvester are presented. The harvester consists of the rigid body suspended by four tension springs and electromagnetic transducers. Once the two resonant frequencies and the mass properties are specified, both the constant and the positions for the springs can be determined in the closed form. The designed harvester can locate two resonant peaks close to each other and forms the extended frequency bandwidth for power harvesting. Halbach magnet array is also introduced to enhance the output power. In the experiment, two resonant frequencies are measured at 34.9 and 37.6 Hz and the frequency bandwidth improves to 5 Hz at the voltage level of 207.9 mV. The normalized peak power of 4.587 mW/G² is obtained at the optimal load resistor of 367 Ω.

• 연구논문집
• /
• 통권34호
• /
• pp.87-99
• /
• 2004

A spring tension control device is used as a very important part of an twister system. The friction force of tensioner must keep same friction force during winding in package. For satisfy this function, many device used common compression coil spring. In this paper, by using the case-building technique which was based on simple theory that unknown design variables are induced by given input design variables by the designer, design automation algorithm about rectangular section compression springs with elastic characteristic is developed. Four design equation are justified in using of analysis of torsion of straight bar of rectangular section and geometrical condition of coil spring. Four design equation and nine design variables are computed by case-building technique.

• Geomechanics and Engineering
• /
• 제2권4호
• /
• pp.281-302
• /
• 2010

An extended model for the response of a rigid footing on a reinforced foundation bed on super soft soil is proposed by incorporating the rough membrane element into the granular bed. The super soft soil, the granular bed and the reinforcement are modeled as non-linear Winkler springs, non-linear Pasternak layer and rough membrane respectively. The hyperbolic stress-displacement response of the super soft soil and the hyperbolic shear stress-shear strain response of the granular fill are considered. The finite deformation theory is used since large settlements are expected to develop due to deformation of the super-soft soil. Parametric studies quantify the effect of each parameter on the stress-settlement response of the reinforced foundation bed, the settlement and tension profiles.

• 한국전산구조공학회논문집
• /
• 제24권1호
• /
• pp.33-41
• /
• 2011

본 연구에서는 비부착형 포스트텐션 시스템의 해석에 적용할 수 있는 모델링기법을 제시하였다. 모델링은 유한요소 해석 프로그램을 이용하였으며, tube-to-tube contact 요소를 도입하여 강연선의 물리적 형상을 직접적으로 모델링하는 방법과 실제의 강연선 외에 가상의 강연선을 콘크리트에 매입하고, 두 개의 강연선을 스프링으로 연결하여 간접적으로 모델링하는 방법을 동시에 제시하고 비교하였다. 콘크리트의 인장경화 현상을 무시하였을때 두 모델링기법에서는 거의 동일한 결과를 제공하지만 콘크리트의 인장경화를 고려한 경우에는 스프링을 이용한 간접적인 모델링기법을 통해서만 결과를 얻을 수 있었으며, 결과 또한 콘크리트의 경화현상을 고려하지 않은 경우와 다소 상이하였다. 비교를 통하여 비부착형 포스트텐션 시스템의 모델링기법으로 스프링을 이용한 모델링기법을 최종적으로 선정하고 기존의 실험적 연구에서 인용한 실험결과와 해석결과를 비교, 검증하였으며 또한 파라미터 스터디를 통해서 모델링의 적절성을 확인하였다.

• 대한토목학회논문집
• /
• 제7권4호
• /
• pp.73-81
• /
• 1987

본 논문에서는 파랑하중에 대한 Tension Leg Platform(TLP)의 tether와 platform의 동적거동해석에 대해서 연구하였다. tether의 동특성 효과를 적절하고도 간단히 고려할 수 있는 platform 해석모델을 제안하여 platform 운동해석을 수행하였으며, tether에 작용하여 인장력에 기인된 기하학적 강성을 고려한 유한요소법을 사용하여 tether의 거동을 해석하였다. 해석 예제용구조물로는 설치수심이 1000ft 및 3000ft인 두 가상적인 TLP를 선택하였으며, 비교를 목적으로 tether의 동특성 효과를 고려하지 않은 기존모델 및 platform과 tether를 조합한 모델 등에 의한 해석도 수행하여, 그 결과를 본 연구에서 제안한 모델에 의한 platform 운동과 tether의 거동 해석결과와 비교분석하였다. 아울러, tether의 통상적인 휨강성 및 tether에 작용하는 파랑하중이 tether의 거동에 미치는 영향정도도 고찰하였다.