摘 要
21世紀(jì)是海洋的世紀(jì)，海洋成為國家綜合國力競爭的制高點，經(jīng)略海洋、興海強(qiáng)國已經(jīng)成為我國國家發(fā)展戰(zhàn)略的重要內(nèi)容。近年來國際海洋工程界掀起了研究超大型海洋浮式結(jié)構(gòu)物(VLFS——Very Large Floating Structure 簡稱VLFS)的熱潮。超大型浮式結(jié)構(gòu)物可用于海上補(bǔ)給、科考、能源基地以及海上城市等。出于我國國情，我們國家對超大型浮式結(jié)構(gòu)物也開始進(jìn)行了一系列概念論證。
本文研究的超大型浮式結(jié)構(gòu)物由多個半潛式模塊組成，各個模塊間采用連接器進(jìn)行連接，連接器采用柔性連接器，允許模塊間的相對運動來減小連接器載荷。
超大型浮式結(jié)構(gòu)物在營運過程中可能會遇到飛機(jī)墜落，船舶碰撞等事故情況。事故載荷不僅會對超大型浮式結(jié)構(gòu)物的局部結(jié)構(gòu)產(chǎn)生破壞作用，而且會對超大型浮式結(jié)構(gòu)物的薄弱環(huán)節(jié)——連接器產(chǎn)生附加載荷。本文對船舶碰撞載荷對超大型浮式結(jié)構(gòu)物載荷的影響進(jìn)行了數(shù)值模擬。以船舶碰撞為例，采用簡化的RMFC模型，然后通過SESAM軟件計算水動力系數(shù)，將其代入多剛體運動微分方程后用數(shù)值方法求解，研究沖擊載荷對連接器載荷的影響。將考慮模塊間相互影響與不考慮模塊間相互影響的結(jié)果進(jìn)行了比較。比較表明在浪向角較大時，以及連接器剛度較大時可以不考慮模塊間相互影響。
本文提出了兩種數(shù)值解法，一種為簡化頻域解法，采用固定頻率的水動力系數(shù)和波浪力，另一種為時域解法，通過頻域中求得的水動力系數(shù)來計算時域的附加質(zhì)量和記憶函數(shù)。兩種解法表明在初步設(shè)計階段采用簡化頻域方法來估算連接器載荷是可行的。
對不同連接器剛度以及不同撞擊部位工況進(jìn)行了比較，找到了載荷較小的連接器剛度以及導(dǎo)致連接器載荷最大的碰撞部位。同時比較了三種簡化碰撞載荷模型，計算結(jié)果表明不同簡化碰撞載荷模型差異不大，連接器碰撞載荷與碰撞沖量有關(guān)。比較了不同碰撞角度的計算結(jié)果，表明連接器載荷與碰撞的力矩很有關(guān)系。
最后本文計算了同時考慮波浪和碰撞載荷的計算結(jié)果，驗證了碰撞載荷對連接器載荷影響的程度，估算出碰撞引起的連接器載荷的數(shù)量級，表明碰撞載荷對超大型浮式結(jié)構(gòu)物連接器的影響不可忽略。

關(guān)鍵詞 超大型浮式結(jié)構(gòu)物；移動海上基地；連接器；碰撞；時域分析；頻域分析





Abstract
The 21st century is the century of ocean. Ocean is the commanding heights of competition of comprehensive national strength. Sea power has become an important part of national development strategies. International marine engineering in recent years launched a study of very large floating structures (VLFS - Very Large Floating Structure referred to VLFS) of the boom. VLFS can be used as offshore supply, or scientific research, energy and maritime cities base. For the conditions of our country, our country has begun a series of proof of concept on VLFS.
VLFS studied in this paper is a kind of VLFS which is made up of several semi-submersible modules. The modules are connected with connectors. The connectors are soft to allow relative motion to minimize the connector load.
VLFS may meet with accidental damage due to airplane collision, ship collision, etc. Accidental loads will not only damage local structures of VLFS, but also induce additional loads on connector which is the weakest part of VLFS.The influence of ship collision on the VLFS is calculated by numerical solution.Taking ship collision as an example, by the use of simplified RMFC model, hydrodynamic coefficient is calculated by SESAM software. Then the hydrodynamic coefficient is taken into multi-body motion differential equation, and this equation is solved with numerical methods to study the influence of impact load on the connector load. The result considering the influence between modules and without considering the influence is compared. It indicates that the influence between modules can be neglected when the wave approach or the stiffness of connector is large enough.
Two numerical methods present here: the first is simplified frequency-domain solution which fixed frequency hydrodynamic coefficient and wave force is applied. The second is time-domain solution which the hydrodynamic coefficient is applied to calculate the added mass in infinite frequency and memory function. It is shown that the simplified frequency-domain solution is available in preliminary design stage of VLFS.
The result of different connector stiffness and collision position is compared. The stiffness of connector which cause minimum connector load and the collision position which cause maximum connector load is found. The three kind of simplified collision load models are compared. It is shown that there is slight difference between these models. The connector load is related with load impulse. The result of different collision angle is compared. It is shown that the connector load is related with the load moment
In the end of this paper, the connector load considering wave and collision load is calculated. The degree of influence is verified. The order of magnitude of connecter loads induced by collision is estimated. The result is shown that the influence of collision load cannot be neglected.
Key words: Very Large Floating Structure, Mobile offshore base, Connector, Collision， Time-domain solution, frequency-domain solution





























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