PSI - Issue 5

Zuheir Barsoum et al. / Procedia Structural Integrity 5 (2017) 377–384 Fikri Bashar Yalchiner/ Structural Integrity Procedia 00 (2017) 000 – 000

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the optimal treatment procedures. For this reason, the current guidelines are intended to provide only general recommendations especially with respect to operator training, procedures and inspection. Speci fi c operator training is provided by the tool manufacturers. Speci fi c treatment and requirements can normally be developed in cooperation with the HFMI device manufacturer. The recommendations in this guideline are dedicated to structural steels only. Studies on HFMI treated welds in aluminum and stainless steel structures exist to a limited extend where fatigue life improvements are observed. Moreover, additional data are necessary to establish recommendations for design. Chapter 1. Introduction Brief description and background of existing weld toe improvements techniques are given along with overview of existing post weld improvement techniques. Chapter 2. High Frequency Mechanical Impact (HFMI) Advantages of HFMI over other improvement methods and historical background of it and equipment used explained. Chapter 3. HFMI Procedures Main aspects of applying HFMI for welded structures such as; ‘Operator Training’, ‘Weld Preparation’, ‘Safety Aspects’ and ‘Weld Toe Treatment’ are clarified. Chapter 4. Quality Control Due to differences in the HFMI tools and the wide variety of potential applications, certain details of proper treatment procedures and quantitative quality control measures are presented generally. Chapter 5. Fatigue Strength Using HFMI The chapter includes design resistance curves based on; nominal stress, structural hot-spot stress and effective notch stress assessment methods. Appendix 1. HFMI Procedure Specification As a quality assurance measure, HFMI specification is given as a table. Appendix 2. Design Examples Four examples are provided based on nominal stress design, structural hot spot stress design and effective notch stress deign for structures subjected to R ratio and variable amplitude loadings. The guideline consists of five chapters and two appendices. They are outlined briefly as follows: In Arabian Gulf there are number of fixed offshore platforms which have exceeded their design life or coming very close to the end of it. Due to economic reasons current trend is to extend the life of the structure as well as amend additional facilities. In order to re- assess these structures’ remaining life detailed fatigue analysis must be carried out by taking into consideration various factors. Since the structure is old, it may not be possible to find readily enough data to re assess its fatigue life. All available data should be collected such as; previous design reports, soil reports, old and new environmental (wave & current) data , survey reports (corrosion & marine growth) to obtain the as is condition of the structure in order to perform an accurate fatigue life estimation. The global spectral fatigue calculation is performed in a tailor made offshore structure analysis software, SACS while a general finite element software, ANSYS can be used for calculating stress concentration factors (SCF) based on structural hot spot stress method.[17] 5. Onsite Potential Applications for Joints in Fixed Offshore Structures

5. 1.Example Fixed Offshore Structure

Figure 3 shows a 50 years old fixed offshore platform on which new extensions will be added and expected to have an additional 20 years of life time.