Stress concentration factors and spectral fatigue assessment of a clamped joint tripod | |
| Author | Pantawat Chuencharoensuk |
| Call Number | AIT Thesis no.OTM-12-04 |
| Subject(s) | Stress concentration Offshore structures Joints |
| 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-12-04 |
| Abstract | Fatigue life assessment of fixed offshore structure is practically determined by performing spectral fatigue using stress concentration factor derived from Efthymoiu formula. The formula was strictly applicable for tubular joint only. The fatigue life assessment of offshore structure with clamped joint using above-mentioned equation is not valid. The accurate SCF of clamped joint is required for fatigue assessment. This study attempts to determine the SCFs by clamped joint by performing Finite Element Analysis (FEA). The fatigue life of structure was then re-assessed with newly derived SCF.The Finite Element Analysis (FEA) is taken care by ABAQUS program. The SCF results compared to each case including reduced bolt pretensions, reduced stiffener plate thickness, the absence of stiffener plates and Efthymiou’s formula would be performed for SCF assessment. This study is to re-assess fatigue life with newly derived SCF .The spectral fatigue analysis is a method that could be used to determine fatigue life of each joint of tripod platform. The results show that the average of difference of SCF is around 5% when reduces bolt pretensions of 10 and 20% for all locations and for all load cases.The average of difference of SCF is around 78% when reduces stiffener plate thickness of 50% and 100% for all locations and for all load cases.In conclusion, the effect of stiffener plates is very sensitive to SCFs when compare with the effect of bolt pretensions for all locations. Most of SCF values for clamped joint using FEA are less than SCF values derived from Efthymiou’s formulas.The SCFs are not constant as varying the magnitude of load because effect of non-linearity of hot spot stress at weld toe. The suitable SCF value has to be selected to make the spectral fatigue. The magnitude of load that is corresponding to maximum end member forces was selected for the sea state. The fatigue life values from FEA are better than the fatigue life values from Efthymiou’s formulas.The sensitivity study indicate that stiffener plates and bolt pretension does not affect to the fatigue life for clamped joints. |
| Year | 2012 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. OTM-12-04 |
| 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) | Punchet Thammarak |
| Scholarship Donor(s) | Royal Thai Government Fellowship |
| Degree | Thesis (M. Eng.) - Asian Institute of Technology, 2012 |