Investigation into the effect of non-linear soil stiffnesses to riser fatigue life (in deep water scenario) | |
| Author | Rittichai Sukbanjongwatthana |
| Call Number | AIT Thesis no.OTM-09-12 |
| Subject(s) | Soil piping (Hydrology) Steel, Structural--Fatigue |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Offshore Technology and Management, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. OTM-09-12 |
| Abstract | As steel catenary risers (SCRs) are becoming widely used for deepwater field development, more understanding in SCRs behavior is necessary for engineers to cope with specific requirements. Stress in SCRs especially during interaction with seabed is needed to be captured in order to accurately predict fatigue life of the riser. This paper studies the effect of non linear soil stiffness to riser fatigue life. Three models are used to simulate and compared soil pipe interaction behavior in order to observe the effect of non linear soil stiffness. Based model is linear model which is created to be the criteria. Linear model assumes that reaction force varies linearly with displacement enabling constant contact stiffness. Non linear model is created with considering non linear soil pipe interaction properties. This model takes the effect of inconstant contact stiffness into consideration when the soil pipe interaction takes place. The last model is elasto plastic model which concerns non linear soil properties. Soil properties such as soil density, undrained shear strength, yield stress and plastic strain are inputted to the model. These factors convey non linear effect to the model. Analysis cases are obtained from industrial practice analysis cases which are provided by DeepSea Engineering & Management Inc. Loads are simulated in terms of buoy movements in all degrees of freedom. Simulation is performed by using ABAQUS. Reaction force, stress and displacement are extracted and analyzed. Responses from elasto plastic model exhibit more sensitive to interaction between seabed and riser than non linear model which result in higher stress variation when loads are applied. Therefore, fatigue life from elasto plastic model shows shorter life time than other two models which implies the effect of non linear soil stiffness to the fatigue life of riser. |
| Year | 2009 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. OTM-09-12 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Offshore Technology and Management (OTM) |
| Chairperson(s) | Chiu, Gregory L. F.;Pornpong Asavadorndeja; |
| Examination Committee(s) | Pennung Warnitchai; |
| Scholarship Donor(s) | Chevron Thailand Exploration and Production Ltd.; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2009 |