In this paper, the shape adjustment algorithm of the spoked wheel cable structures with retractable membrane system is studied. The initial tension of the membrane or cable is necessary to form the structure and its value is determined by the design shape. However, due to internal and external environmental influences, its shape may be different from the initial designed shape. In the case of the cable structures covered in this study, tension adjustment is necessary to maintain the designed shape because it influences the tension of the cable depending on the state of the retractable membrane. Therefore, we proposed an adjustment algorithm of an initial shape based on the force method. The effectiveness and validity of the methodology were examined through the applicable cable structures. The results of the shape adjustment analysis of the symmetric spoked wheel cable model were reliable and accurate results were obtained.

Sometimes, it is impossible to install a sensor on a certain location of a structure due to the size of a structure or poor surrounding environments. Even if possible, sensors can be frequently malfunctioned or improperly operated due to lack of adequate maintenance. These kind of problems are solved by the virtual sensing methods in various engineering fields. Virtual sensing technology is a technology that can measure data even though there is no physical sensor. It is expected that this technology can be also applied to the construction field effectively. In this study, a virtual sensing technology based on ARX model is proposed. An ARX model is defined by using the simulated data through a structural analysis rather than by actually measured data. The ARX-based virtual sensing model can be applied to estimate unmeasured response using a transfer function that defines the relationship between two point data. In this study, a simulation and experimental study were carried out to examine the proposed virtual sensing method with a laboratory test on a cable-stayed model bridge. Acceleration measured at a girder is transformed to estimate a cable tension through the ARX model-based virtual sensing.

Porcelain surge arrestor is very vulnerable to earthquake but there is very few information on its dynamic characteristics which are necessary to the seismic design. Therefore, the dynamic characteristics of the porcelain surge arrestor are evaluated considering the variation of its cable tension and stiffness by shaking table test. The test results show that the first natural frequencies are 5.3 Hz and 5.2 Hz in the horizontal x- and y-axis directions, respectively, and higher than 30 Hz in the vertical z-axis direction, respectively. The installation of cable on the surge arrestor reduces the horizontal natural frequencies due to the constraint effect of the cable but cable tension has no effect on the natural frequency. Also, the natural frequency is proportional to the stiffness of the surge arrestor. This test result will be used for the seismic design and seismic capacity assessment of domestic substations and contribute to the stability of the electric power supply under earthquake event.

The method based on various mathematical characteristic equations for identifying tensile forces in the cable structure system are used as response data to reflect the properties of the dynamic sensitivity. The vibration tests have been conducted with respect to levels of applied weight for the sagged cable. In this study, a set of natural frequencies are extracted from the measured dynamic data. Next, existing characteristic equation methods based these extracted natural frequencies are applied to identify tensil forces of the sagged cable system. Through several verification procedures, the proposed methods could be applied to a sagged cable system when the initial material data are insufficiency.

사장교의 시공에 있어서 보강형과 주탑의 형상 및 케이블 장력은 형상관리시 주요한 관리 항목이다. 특히 보강형의 형상은 Keg Segment의 원활한 폐합뿐만 아니라 계획된 종단 및 횡단 선형을 구현하기 위해 필수적으로 관리되어야 한다. 사장교에서 단계별 시공을 진행함에 따라 보강형 레벨과 케이블 장력 오차는 피할 수 없으며, 이러한 오차는 크게 재료 물성치와 모델링상의 오차, 제작 및 시공에 의해 발생하는 오차 등으로 나눌 수 있다. 이러한 오차로 인 해 케이블의 장력과 구조물의 처짐 또는 변위가 이론적인 해석값과 다르게 나타나며, 이에 대한 보정은 케이블의 길이 조정으로 수행하게 된다. 본 연구에서는 제2돌산대교에서 사용된 오차를 보정하는 새로운 최적화 기법을 소개 하고자 한다.

현수교 행어케이블의 장력은 현수교의 상태점검에 있어 중요한 요소이다. 현재 케이블의 장력 추정에는 여러 이론식에 의한 간접적인 방법들이 사용되고 있으며, 케이블의 가속도신호로부터 고유진동수를 측정한 후 고유진동수와 장력과의 관계로부터 케이블의 장력을 추정하는 진동법이 대표적이다. 하지만 운동방정식을 기반으로 하는 진동법은 휨강성의 영향이 큰 짧은 케이블의 장력추정에는 적합하지 않다. 본 논문에서는 10m 미만의 짧은 케이블에 대해서도 전기 가능한 새로운 장력 추정 방법으로 단변분탐색법과, 최적화 기법을 이용한 역해석 기법을 제시하였다. 이론에 대한 검증을 위해 국내에 사용 중인 광안대교 행어케이블을 대상으로, 역해석과 진동법에 의한 추정장력들과 설계장력을 상호 비교하였고, 이를 통해 역해석기법이 길이에 상관없이 장력추정에 유용하다는 결론을 얻었다.

In a recent construction industry, cable supported sσuctures such as a cable-stayed bridge or space stadium have been increasingly constructed according to rapidly upgrade their related technologies. Generally stay cables as a critical member need to be rearranged for being satisfied with design tension forces. In this purpose, a vibration method has been applied to estimate the tension forces exerted on existing stay cables. In this study, cable vibration tests were carried out to evaluate the cable tension forces comp와ing with theoretical and practical formulas. Using the measured frequencies ob않ined from free vibration and impulsive tests, an accuracy of the estimated tension forces is confirmed according to use the first single mode only or higher multiple modes.

This study is aimed to predict the configuration and tension of a towing cable of a side-scan sonar which plays an important role in developing ocean resources. The governing equations of 3-D static equilibrium equations for a flexible cable are derived and solved using a finite difference method. The forces considered in this paper are effective weights, drag forces due to currents and ship moving, and the tension at both ends of the towing cable. The governing equations are non-linear, so an iteration method is applied to solve the equation. A case study is carried out for several different conditions. The result will be useful for predicting the location of a side-scan sonar and to design the towing system.

케이블 교량에서 케이블은 가장 중요한 구조부재의 하나이며, 케이블의 내부 장력을 모니터링하는 것은 케이블 교량 유지 관리에서 필수적이다. 본 연구에서는 케이블 장력을 효율적으로 모니터링하기 위한 무선센서 기반의 장력추정 자동화 시스템을 개발하였다. 무선센서에 포함된 가속도계를 통해 케이블의 진동을 계측하고, 진동기반 장력추정법을 통해 케이블의 장력을 추정하였다. 장력추정 절차를 자동화하기 위해 가장 널리 사용되고 있는 기계학습법의 하나인 합성곱 신경망을 도입하였다. 개발된 자동화 기법은 싱글보드 컴퓨터의 하나인 라즈베리파이3 모델B+에 구현하였으며, 실험실에서 모형 케이블을 이용하여 성능을 검증하였다. 케이블의 장력이 바뀌는 경우에도 개발된 시스템은 자동으로 변화된 장력의 크기를 잘 계측할 수 있는 것을 확인하였다.

The wireless sensor prototype was developed and the field test result, natural frequencies of each mode in stay-cable, showed 0.5% difference compared to the wired sensor. Also, the cable tension derived by the vibration method was 1.177% difference. As a sensor for managing cable tension, the applicability to bridges was confirmed. In the next study, LoRa LPWAN technology will be applied to various sensors used in structures.

A damage case of parallel strand cable anchorage was introduced, in which 7 strands were slipped from each wedge at the anchorage of the cable stayed bridge in service. Also, a cable damage detection scheme was proposed on the basis of tension force measurement and model updating method by least square estimation to minimize tension variation. The proposed scheme has been verified from analytical simulations and the actual damage case. The damaged cable leading to tension variation more than noise level of cable force measurement was successfully detected with 7~8 strands damage indication of 2% error in the actual strand slippage case.

In this study, digital image processing was used to estimate the tensile forces of the remote hanger cable using image-based back analysis method. A portable digital camcorder was used as a vision-based system considering convenient and economical aspects for use. The ambient vibration test was performed on a suspension bridge to verify the validity of the image-back analysis method of measuring the hanger cable tensile force.

In the cable wall system, the cable tension force can be changed by the various reasons. After 10 years from the construction of cable wall system in Hamad Medical City Womens Hospital of Qatar, an average of about 16% of the tension force was decreased. Since the tension loss can affect the structural capacity and stability, the re-tightening was carried out up to about 90% of the design tension. Also, the annual regular inspection including the measurement of cable tension is proposed as the maintenance plan.

Currently, the cable safety management of cable supported bridges is calculated by the ratio of the measured tension to the design tension. The measurement of the tension is performed by indirectly estimating the acceleration measured at the cable surface in terms of the tension. The method of converting the cable vibration response (acceleration) into the tension is disadvantageous in that the damage of the individual strand (or wire) in the cable is not clearly reflected in the tension because the measurement is not reliable and is managed only by the total tension. The purpose of this study is to improve the cable safety management system by evaluating how the damage of individual strand of MS type cable, which is mainly applied to cable-stayed bridges, affects the safety level managed by level of cable tension.

In this study, the method of measuring cable tension using the vision-based system was proposed, and a portable digital camcorder was used as a sensor for the measurement of the cable tension positioned at remote distances, considering the user convenience and the cost-efficiency. The vibration method (accelerometer, vision-based system) was used to measure the cable tensions, and the result was compared and analyzed.

This study analyzes the error factors of cable tension estimation method using linear regression and suggests the upper and lower limits of tension error. The tension estimation method using linear regression is affected by errors such as boundary condition, natural frequency, cable length, and mass density. The boundary condition error analyzes the error rate for the case where the error occurs the greatest. The error of mass density and length is analytically derived, and the error of measurement natural frequency is analyzed by Monte Carlo simulation. Among these errors, the boundary condition error and the measurement natural frequency error are expected to be able to present the upper and lower limits of the error that can be caused to the estimated tension by the corresponding error factor.

Because of the characteristics of long-span bridges, the cable tension is considered a critical item in their maintenance. In particular, because the evaluation of the cable tension in a suspension bridge is essential for understanding the general status of the structural system, identifying the initial values of this force in the construction of a bridge and then accurately predicting and comparing its estimated values during traffic use are very important tasks for the maintenance of a suspension bridge. In this paper, to verify the algorithm for estimating the cable tension of hanger cables using the back analysis technique, an ambient vibration test was conducted at a suspension bridge.

케이블지지교량에서 케이블은 하중을 지지하는 주요 부재로, 케이블 장력은 교량의 건전성과 안전도 평가에 있어서 매우 중요한 변수이다. 케이블의 장력을 추정하는 기법으로, 로드셀 및 유압잭 등을 이용하여 케이블의 응력을 직접 측정하는 직접법과 케이블의 형상조건과 계측된 동특성을 활용하여 장력을 역산하는 진동법이 가장 많이 활용되고 있다. 최근 들어 케이블 내부 강재의 응력변화로 인하여 유발되는 자기장 변화를 탐지하는 EM 센서의 연구 및 활용이 증가하고 있다. 본 연구에서는 리프트오프 테스트, EM 센서 및 진동법(Vision-based System, Accelerometer)을 적용하여 장력을 측정하고 그 결과를 비교 분석하였다.