Failure characteristic analysis of tensile armour layer of unbonded flexible riser under axial compression

ABSTRACT

Unbonded flexible risers have been applied in the harsh environment for several decades, and structural failure sometimes appears. Owing to the large axial compression by installation or to the combined loads of axial compression and external pressure during operation, radial or lateral failure of tensile armour layers can occur, threatening structural safety. In order to study the mechanism of failure on tensile armour layers of unbonded flexible riser subjected to axial compression, a simplified numerical model, based on ABAQUS/Explicit, with tensile armour layers, structural tape and outer sheath is proposed. The nonlinearity of material is taken into consideration in this model and the validity of this model is verified by a theoretical method. Failure characteristics for helical wire under axial compression are studied in consideration of the nonlinear factors including number of tendons for the tensile armour layer, laying angle of the tensile armour layer, thickness of outer sheath and friction coefficient between layers. In addition, the impact of the external pressure on axial ultimate strength is discussed.

KEYWORDS:

• Unbonded flexible riser
• simplified numerical model
• failure
• ultimate strength
• axial compression

Notes on contributors

Qing-Sheng Liu, PhD Candidate, Shanghai Jiao Tong University.

Hong-Xiang Xue, Associate Professor, Shanghai Jiao Tong University.

Xiao-Yuan Liu, Master Student, Shanghai Jiao Tong University.

Wen-Yong Tang, Shanghai Jiao Tong University.

Additional information

Funding

This paper is based on the projects supported by the National Natural Science Foundation of China (grant number 51579146) and Shanghai Science and Technology Committee Rising-Star Program (grant number16QA1402300).