Physical Model Study Of Interaction Between Sea Ice And Offshore Structures

Sea ice disasters. environrnents and loads are the key controlling facors fOrconstrUction of offshore trictUres in Bohai se4 accordingly, how to predict iceforces on smictUres has been paid more and more attention. Howevef, because of thecomPlexity of sea ice mechanics, an acknowledged physical model describing theinteraction mechanism betWeen ice and struCfores has not been developed. FieldinveStigation is considered as the most effeCtive method to obtain first-handmaterials, bul it is difficult to measure directly because of the high expense,comPlicated conditions and execrable environment. Therefore, the main work of thispaPer is to stUdy the interaction mechanism betWeen ice and trictUres by aPplyingphysical model experiments.The maldng technology of DUT-l non-refogerated synthetic model icedeveloped by State Key Laboratory of Coastal and Offshore Engineering, DalianUniversity of Technology in l999 is introduced in the second chaPter of thes paPerAlso the experimental equipment and measdring methods for model icepefformances and ice and strUctUres interaction is described. The exPeriments ofstatic ice forces on vertical pile are conducted to confirm the feasibi1ity of usingDUT- 1 model ice in physical model tests.The third chaPter is mainly concemed with the physical model tests of static iceloads on conical stos. In tests the horizontal and vertical ice fOrces aremeasured by the load sensors and the process of model ice acting on the triAn ismonitored by a CCD camera from the top of the steel frame and successive imagesare taken by the computer. The measured ice fOrces are compared to and agree wellwith the predicted results of Croasdale's and Ralston's theoretical model. Powerspectra of ice fOrces are derived from measured ice load time series with the methodof Fast Fourier TransfOrm and the relationship between characteristic ice fOrces andzero order momellts are shown. Also the effect of various parameters, such as icevelocities, inclined angles, waterline diameters and breaking modes on ice forcesand spectral parameters are discussed and the regularities are found.In the fourth chaPtCr of this paPet, physical model exPeriments of ice acting onsemi-circle breakwatr are cAned out. Two different ice thickness and five differenttrigent angles of Watr line are adopted. Tests on incline wall are conducted first inorder to verify the reliability of experiments and comparison shows tha results ofincline wall tCstS agree well with theoretical results of two-dimension model.MaxAnurn values. average values and significan values of ice forces are derivedfrom analyzing measured ice force hme series and the relationship between ice forcecharacteristic vaIues and zero order momenis is achieved. According tO the analysisof test data, Primarily formula p9tt6m of ice forces on semi-circle breakwater is setuP and the coefficients in formula are determined by least-square method. ComPutedresultS with measured physical and mechboc parameters agree well with measuredresults and regression coefficient is uP to 0.9, which testifies rationality of theformula adeqUaelyOn the basis of static experiments, dynaxnic interaction tests betwCen ice andconical strUCtUres are conducted(seen in ChaPter flve). Appropriate modeldimension and metal material are chosen. StructUre frequency is controlled toaPproximate the range of ice tallure frequency, in order that the resonance ordynarnic magnification may occur StrUCtUre acceleration. displacement and Strainare measured from sensors on model simcture and sampled by comPlltCr ThecharaCteristic frequency of strUctUre can be derived from analyzing resPonse ofsimctUre disPlacement and dynamic ice forces on smictures are achieved bycombining resPOnses of strUcfor disPlacemellt and acceleration.In ChaPtCr six, a stochastic model for dynamic interaction betWeen ice andoffshore sAncfore is set up by asstalng ice thickness a random variable obeying...