Bonded Flexible Pipe Model Using Macroelements

Flexible pipes are structures composed by many layers that vary in composition and shapes. The structural behavior of each layer is defined by the role it must play. The construction of flexible pipes is such that the layers are unbounded, with relative movement between them. Even though this characteristic is what enables its high bending compliant behavior, if the displacements involved are small, a bonded analysis is interesting to grasp the general characteristics of the problem. The bonded hypothesis means that there is no movement relative between layers, which is fine for a small displacement analysis. It also creates a lower bound for the movement, since when considering increasingly friction coefficient values, it tends to the bonded situation. The main advantage of such hypothesis is that the system becomes linear, leading to fast solving problems (when compared to full frictional analysis) and giving insights to the pipe behavior. The authors have previously developed a finite element based one called macroelements. This model enables a fast-solving problem with less memory consumption when compared to multipurpose software. The reason behind it is the inclusion of physical characteristics of the problem, enabling the reduction in both number of elements and memory used and, since there are less elements and degrees-of-freedom, faster solved problems. In this paper, the advantages of such model are shown by using examples that are representative of a simplified, although realistic, flexible pipe. Comparisons between the macroelement model and commercial software are made to show its capabilities.