中文摘要：

深海SPAR平台在环境载荷作用下的运动稳定性问题已经成为当前的研究热点。文章采用理论分析和数值模拟相结合的方式，在不考虑系泊张力影响并且满足组合共振条件情况下，探讨当波浪幅值达到一定程度时垂荡、纵摇响应的局部分岔现象。结果表明：在组合共振发生时，垂荡、纵摇响应均变得不稳定，而且纵摇响应幅值较大；垂荡固有频率与两倍的纵摇固有频率之间的偏差越大，激起纵摇分岔现象需要的波浪幅值越大；波浪频率在一定范围内的变化对a5曲线影响不大，但当波浪频率与垂荡和纵摇固有频率之和的偏差超过一定范围时组合共振现象会消失。

英文摘要：

The movement stability problem of SPAR platform in deep sea under the environmental conditions has become a research hotspot. In the case of not considering mooring tension effect and meeting the com-bination resonance conditions, this paper discusses the part of bifurcation phenomenon when wave ampli-tude reaches to a certain extent, using the way of theoretical analysis and numerical simulation. The results show that the heave and pitch motion will get unstable and the pitch response amplitude will become larg-er when combination resonance occurs. The critical wave amplitude of bifurcation phenomenon will become larger when the deviation between heave natural frequency and doubled pitch natural frequency augments. The wave frequency within a certain range of change has less effect on the a5 curve. But the combination resonance will not be induced if the deviation between wave frequency and heave natural frequency goes beyond a certain range.