Investigation Of Design And Analysis For Unbonded Flexible Pipe Structural

Flexible pipe is the most important ways to transport oil and gas in the oceanographic engineering. Unonded flexible pipe is widely applied for transportation with superior mechanical properties and designability. Unbonded flexible pipe is a composite structure built up of several steel layers (carcass layer, pressure armor layer and tension armor layers) and polymer layers(inner sheath layer, anti-wear layer and outer sheath layer). The main characteristics of the pipe is composed of a variety of functional layers with helical structures and unbonded form. So contact, friction and slip may occur between the layers, which bring a huge challenge for design and analysis of the pipe under the environment load and floating.This paper proposed a design method that based on the failure modes after research the structure and status of unbonded flexible pipe from domestic and overseas, and give the design process to guide the pipe design. Considering of the pipe will subjected to tensile and external pressure loads. The paper build appropriate finite element models to analysis tension and collapse mechanical behaviors. Then verify the tensile stiffness simulation result with laboratory prototype. A three dimensional finite element model is developed to simulate the collapse behavior of carcass under external pressure, which consider of geometrical imperfections and material nonlinearity’s effect that were missed in theoretical analysis. So, we get a collapse behavior curve from the collapse model to design the carcass of pipe. Finally, carcass layer and tension armors which belong an example that a riser will be worked in1500m depth of water are designed based on the above finite element models.This research of the dissertation is sponsored by Hi-Tech Research and Development Program of China (863Program,2012AA090314)...