Experimental Study Of Ice-induced Vibration On Flexible Conical Structure

As ocean engineering is developing extensively, the affect of sea ice on structurebecomes important. Therefore, reasonable design and safe operation of structure incold region has gained more attention in both scientific and engineering area. Conicalstructure is a good choice in cold region because of its advantage in reducinghorizontal ice force. Ice induced cone vibration in the real life has brought a strongdemand in the research of dynamic ice force on conical structure and it has alsobecome an important direction in the research of ice force on the cone.Using a jacket platform with up-bending and down-bending cone in the JZ20-2Sea field as the engineering background, this paper has studied ice-induced conevibration by the means of model test in the ice engineering laboratory of TianjinUniversity, gained a lot of data, and achieved some accomplishments. With theobservation of the test phenomena and the analysis of testing data, a two-peakice-induced cone vibration ice force function is proposed. By the comparison of firstpeak ice force in dynamic ice force and peak ice force in static ice force, theassumption that the flexibility of the structure will reduce the first peak ice force isprovided. The ratio between the first peak ice force and the second peak ice force iscompared with diameter/ice thickness ratio and ice speed. The result is ice speed haslittle effect on the ratio between two peak ice forces, while diameter/ice thicknessratio is almost linear to the ratio between two peak ice forces and the relation betweenthem is expressed in a formula. Meanwhile, the period of ice force is gained with thehelp of the relation between breaking length and ice thickness. Through statisticalanalysis of the testing data, the ratio between loading/unloading time in the twobreaking processes and ice force period is gained. With all the above conclusion, theice-induced cone vibration ice force function is finally determined.