National University of Civil Engineering Student: Vũ Văn Hoan Page 1 Class: 47IH Student code: 8136-47 NATIONAL UNIVERSITY OF CIVIL ENGINEERING SUMMARY OF FINAL PROJECT INPUT DATAS FOR PIPELINE FREE SPAN FATIGUE ANALYSIS Professor : PHAN VĂN KHÔI National University of Civil Engineering Student: Vũ Văn Hoan Page 2 Class: 47IH Student code: 8136-47 Student :VŨ VĂN HOAN Student code :8136-47 Class :47IH Hà Nội, June 2007 National University of Civil Engineering Student: Vũ Văn Hoan Page 3 Class: 47IH Student code: 8136-47 TABLE OF CONTENTS SUMMARY 3 Chapter 1. GENERAL 5 1.1. Vietnamese pipeline route systems 5 1.2. Phenomen of pipeline free span fatigue 5 1.3. State of input datas for pipeline fatigue analysis 6 1.4. Domain of project 6 Chapter 2. METHODS OF FATIGUE ANALYSIS FOR PIPELINE FREE SPAN 8 2.1. Culmulative damage rule of Palmgren-Miner 8 2.2. Fatigue curves (S-N curves) 8 2.3. Deterministic method 9 2.4. Spectrum method 9 2.5. Method of the standard: DnV-RP-F105 – Free spanning pipeline 10 Chapter 3. INPUT DATAS FOR FATIGUE ANALYSIS OF PIPELINE ROUTES IN VIETNAM 11 Chapter 4. APPLICATION 12 CONCLUSION 13 National University of Civil Engineering Student: Vũ Văn Hoan Page 4 Class: 47IH Student code: 8136-47 SUMMARY This Final project is named: “INPUT DATAS FOR PIPELINE FREE SPANNING ANALYSIS IN CONDITIONS OF SEA-ZONES IN VIETNAM”. The report includes 4 chapters, 1 conclusion and 2 appendixes. 1. General 2. Methods of fatigue analysis for free span of pipeline 3. Input datas for fatigue analysis for pipeline routes in VietNam 4. Application Conclusion 1. Wave datas for pipeline route Nam Côn Sơn 2. Results of Fatigue analysis National University of Civil Engineering Student: Vũ Văn Hoan Page 5 Class: 47IH Student code: 8136-47 1. GENERAL This chapter gives a gereral view about the pipeline routes system and about occurring probabilty of free spans in VietNamese sea-zones. It also introduces the problem of fatigue analysis for pipeline, and state of input datas for this process in VietNam. Based on the two informations above, this chapter sets the domain of the studies of the project. 1. Vietnamese pipeline route systems Nowaday, systems of pipeline routes are developping strongly with thousands of kms in all over the world. In Vietnam, there are already several pipeline systems, as: gas pipeline route Bach Ho – Ky Van, pipeline systems of Dragon field, Ruby field, Nam Con Son pipeline system… Vietnamese pipeline systems are also being enlarged in scale, in their economic worth. In the future, a number of deep water pipeline route systems plans will be realized in the Southern sea. The observations have shown that, with conditions of the Southern sea, the phenomens of pipeline free span are very popular. Therefor, the problem of pipeline fatigue analysis is required for safety installation and operation phases. 2. Phenomen of pipeline free span fatigue The fatigue phemomen was first studied by Wöhler in 1850. And step by step, it takes a more and more important part in processes of pipeline design and has been recommended in many mairne structure design standards. Recently, the National University of Civil Engineering Student: Vũ Văn Hoan Page 6 Class: 47IH Student code: 8136-47 most wellknown standard of pipeline fatigue in the world is DnV-RP-F105 – Free spanning pipeline. Fatigue of pipeline is caused by the three following causes: - wave direct action; - in-line vortex shedding; - cross-flow vortex shedding. This phenomen may take place in many parts of a pipeline, but only some certain types of charges can make a significant damage which must be taken care of. And in all of the parts of a pipeline, fatigue of free spans on the seabed and fatigue of marine risers are the most considerable that can make them destroyed in installation or operation phase. With free span of pipeline, there are four principal types as the followings: - Free span induced by uneven seabed - Free span induced by uneven underscouring - On-purpose built free span - Free span caused by exceptional event. It is free span pipeline fatigue, which is the object of the studies in this project. 3. State of input datas for pipeline fatigue analysis The problem of pipeline fatigue is required solved in installation and operation phase and must be based on the code of a certain recognized standard. In Viet Nam, it is lack of documents on this problem, especially documents on the input datas of the solving process. Moreover, in fact, several software are used for pipeline fatigue analysis. It is so important to gives correct inputs datas for correct results. National University of Civil Engineering Student: Vũ Văn Hoan Page 7 Class: 47IH Student code: 8136-47 In conclusion, in Vietnam, the input datas for pipeline fatigue analysis have not been systematized. Therefor, a document on this problem is neccesery. 4. Domain of project This project takes concentration in these following problems: 1. Methods of pipeline fatigue analysis systematising 2. Input datas for pipeline fatigue analysis systematising The direct object of the studies is pipeline span. National University of Civil Engineering Student: Vũ Văn Hoan Page 8 Class: 47IH Student code: 8136-47 2. METHODS OF FATIGUE ANALYSIS FOR PIPELINE FREE SPAN This chapter introduces the Culmulative damage rule of Palmgren-Miner, brefly about fatigue curves (S-N curves), 3 methods of pipeline fatigue analysis: deterministic method, probability method and method of DnV Recommended Practice –RP-F105. In this project, deterministic method, probability method are introduced as theories of base and sets the method of DnV standard as the main one. Result of free span pipeline fatigue analysis is fatigue life time of the span or allowable span length, based on the culmulative damage rule of Palmgren-Miner. Here presents three methods to solve this problem: - Deterministic method - Probabilistic method - Method of the standard DnV-RP-F105 – Free spanning pipeline 1. Culmulative damage rule of Palmgren-Miner The rule expresses that: with each level of stress range, S i , the cycles number to failure is N i , if the number of stress cycles is n i , then the corespondant damage is n i /N i , and the total damage of structure is a sumptation of all the damages. The structure is failured when the total damage is equal to unit. National University of Civil Engineering Student: Vũ Văn Hoan Page 9 Class: 47IH Student code: 8136-47 2. Fatigue curves (S-N curves) The rule of Palmgren-Miner requires determination of relation between a stress range and a correspondant number cycles to failure. All of these relations of a structure detailed (or a base material, or a type of welding) makes a fatigue curve of it. For the pipe structure detaileds, S-N curves have a common form: or in a logarithm form : 3. Deterministic method This method base on the asumption: wave is harmonic and current is regular (deterministic). In each period time of wave and current, there are n i cycles of environmental charges, and the received stress S i is deterministic. By choosing a correct fatigue curve, we have the correspondant number cycles to failure N i . The fatigue life time of span will be caculated from the total damage. 4. Spectrum method This is the first of the probability methods to analyse fatigue problem, where waves are considered as probabity processes represented by vary sea states. Each sea state is given by an energy spectrum. The culmulative damage is culculated by basing on the following sumptations: National University of Civil Engineering Student: Vũ Văn Hoan Page 10 Class: 47IH Student code: 8136-47 - the Morison equation is linearized - pipe-soil interaction is linear - the distribution of stress ranges of pipe is Weibull distribution The narrow wave spectratra band with is required. If that is violated, a stress factor will be used to modify the stress process into a equivalent narrow bandwidth process. 5. Method of the standard: DnV-RP-F105 – Free spanning pipeline The code of this standard bases on the assumption: the distributions of wave and current are three parameters Weibull distributions. The pipe fatigue life includes: - life time versus vortex-induced in-line vibrations - life time versus vortex-induced cross-flow vibrations - life time versus direct wave action. The fatigue analysis process is given in 3 screening criterions, 1 fatigue criterion and 1 ULS critertion. Each screening criterion checks if a marginal fatigue life calculation is needed. The fatigue criterion checks if the spanfatigue life time is less than its design life time. The ULS criterion check the stress of pipe in extreme environmental conditions. The marginal fatigue-life-times are defined by response models and a force model. Amplitude response models are empirical models providing the maximum steady state VIV (Vortex Induced Vbration) amplitude response as a function of [...]... FOR FATIGUE ANALYSIS OF PIPELINE ROUTES IN VIETNAM All the types of main input datas for pipeline fatigue analysis and their usages are presented in this chapter For applications in pipeline routes in Vietnamese sea-zones conditions, here provides some useful data patterns From the methods above, this chapter makes a systematization for input datas for pipeline free span fatigue analysis in Vietnamese... vary sea-zones of VietNam (shown in Appendix 1), which can be used in free span fatigue analysis, Student: Vũ Văn Hoan Student code: 8136-47 Page 12 Class: 47IH National University of Civil Engineering 4 APPLICATION This chapter gives an example of pipeline free span analysis, clears up the input datas for this process The example was solved by a programm PIPELINE FREE SPAN FATIGUE ANALYSIS PROGRAMM”,... with more and more large scale, free span fatigue analysis is neccessery and required in many pipeline design standard in the world This project systematised the methods for pipeline free span analysis and the input datas for this process Also here, this problem is solved better and better by a programm written by the authour of this project With many efforts, this project had certain good results... systematised datas are: Materials of pipeline and their technic parameters which are required in free span fatigue analysis; Fatigue curves system for pipeline and their usages Soils and needed parameters for the pipe-soil interation Here also presents a data parttern of seabed soil in sea zones Bach Long and Ca Mau; Current and wave datas, required data types and the usages In the lack of environmental datas. .. University of Civil Engineering the basic hydrodymic and structural parameters The VIV In-line life time and VIV cross-flow life time are defined here The force model base on the wellknown Morison ‘s equation to calculate the fatigue life time versus wave direct action Student: Vũ Văn Hoan Student code: 8136-47 Page 11 Class: 47IH National University of Civil Engineering 3 INPUT DATAS FOR FATIGUE ANALYSIS OF. .. by the authour of the project This programm was written in Visual Basic Application for Excel, includes 8 modules of code, bases on the standard DnV-RP-F105 The received results are clear, logical and acceptable, and are shown in Appendix 2 Student: Vũ Văn Hoan Student code: 8136-47 Page 13 Class: 47IH National University of Civil Engineering CONCLUSION In the tendance of develop of pipeline systems... by the authour of this project With many efforts, this project had certain good results but there are still mistakes Student: Vũ Văn Hoan Student code: 8136-47 Page 14 Class: 47IH National University of Civil Engineering Student: Vũ Văn Hoan Student code: 8136-47 Page 15 Class: 47IH . Phenomen of pipeline free span fatigue 5 1.3. State of input datas for pipeline fatigue analysis 6 1.4. Domain of project 6 Chapter 2. METHODS OF FATIGUE ANALYSIS FOR PIPELINE FREE SPAN 8 2.1. Culmulative. General 2. Methods of fatigue analysis for free span of pipeline 3. Input datas for fatigue analysis for pipeline routes in VietNam 4. Application Conclusion 1. Wave datas for pipeline route Nam. free span of pipeline, there are four principal types as the followings: - Free span induced by uneven seabed - Free span induced by uneven underscouring - On-purpose built free span - Free span