A Estimation of Damping Properties of Stay-cables Using a System Identification Scheme Keun Won Lyu
ABSTRACT Recently the construction of the cable bridge is advanced actively all over the world. In the cable bridge, the length of the center-span is wider than the other bridges and the view is beautiful. So the demand is increasing gradually not only simply objective of traffic and goods movement but also the side of the building which has a symbol characteristic. Comparing in the bridge of generally different type, the width of the cable support bridge narrow relatively, the span length is long and height of the tower is high. Thus it has the structure which is not only the possibility of receiving the effect of the wind or earthquake plentifully. To secure the stability of like this cable support bridge, after we should grasp the quality that the cable is accurate, then apply. In case of not estimating the damping ratio according to the vibrating quality of cable, it is joined together inaccurate design of the cable damper capacity, increase of expense and countermeasure insufficiency. Estimation of the accurate cable damping ratio is necessary to prevent this. This paper explains the static and the dynamic analysis technique of the cable in order to estimate damping ratio of the cable stayed bridge with elastic catenary cable element. Since it is difficult to measure displacement essentially, it estimates damping ratio applying reconstructed replacement by acceleration so that estimates damping ratio by unstable acceleration to apply to the SI. Before estimating the characteristic of the cable damping, it raises reliability of the estimated damping ratio by assuming the unstrained length having a great influence in the natural frequency. It estimates the damping ratio using the SI technique through the free and forced vibration test. Estimated damping ratio of free vibration region is verified using the existing Logarithmic decrement method.
Key Word Elastic Catenary Cable Element, System Identification Scheme, Fundamental Frequency, Damping Ratio, Unstrained length
|