Strukturna analiza rampe za polaganje cjevovoda na morsko dno

professional thesis

• Author: Darko Gunjača
• Mentor: Smiljko Rudan (mentor)
• Committee member: Kalman Žiha (predsjednik povjerenstva)
• Committee member: Smiljko Rudan (član povjerenstva)
• Committee member: Joško Parunov (član povjerenstva)
• Committee member: Ivica Skozrit (član povjerenstva)
• Committee member: Željan Lozina (član povjerenstva)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2013-12-11, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Shipbuilding

Abstract

Rampe za polaganje cjevovoda na morsko dno složene su rešetkaste konstrukcije izložene značajnim
opterećenjima prilikom rada. Ta opterećenja, a uz njih i projektni zahtjevi, rastu s povećanjem dubine
mora na kojoj se cjevovod polaže. Brod Pieter Schelte, u vlasništvu tvrtke Allseas, bit će dovršen
2014. godine i moći će cjevovod polagati na dubinama do 3500 m. U okviru ovog specijalističkog rada
provedena je strukturna analiza rampe tog broda, na osnovi nacrta koje je ustupilo brodogradilište
NMC iz Nizozemske.
Polaganje cjevovoda tim brodom odvija se S-lay postupkom. Stoga je na početku rada opisan taj
postupak, a zatim je analizirana ravnoteža sila koje se pri takvom polaganju pojavljuje. Pravila
klasifikacijskih društava opisuju značajke koje takva konstrukcija mora posjedovati. U ovom radu
korištena su pravila društva Det Norske Veritas za analizu okolišnih uvjeta i opterećenja (DNV-RPC205) i karakteristika cjevovoda (DNV-OS-F101), kao i API pravila za projektiranje nepomičnih
odobalnih konstrukcija (API-RP2A).
Za potrebne strukturne analize generiran je globalni model rampe koji je opterećen sukladno scenariju
polaganja cjevovoda na najveću dubinu. Na osnovi rezultata određena su područja najvećih naprezanja
i kritični strukturni detalji. Oni su dalje analizirani tehnikom podmodela prve razine ljuskastim
konačnim elementima i druge razine, volumnim konačnim elementima, do razine zavara. Na osnovi
pravila za proračun zamora čeličnih odobalnih konstrukcija (DNV-RP-C203) provedena je analiza
žarišnih naprezanja i faktora koncentracije naprezanja odabranog strukturnog detalja. Konačno,
učinjena je analiza zamornog vijeka strukturnog detalja izvrgnutog najvećem opterećenju, tijekom
pretpostavljenog radnog vijeka rampe i broda od 30 godina.

Abstract (english)

Stingers for pipe laying on seabed are complex pipe structures exposed to significant loads during pipe
laying operation. These loads, and with them design requirements, increase with depth of sea where
the pipeline is laying. Pieter Schelte vessel, owned by Allseas, will be completed in 2014 year and will
be able to lay the pipeline at sea depths up to 3500 m. In this thesis structural analysis of ship stinger
was conducted according to drafts provided by NMC, shipbuilding company from Netherlands.
Pipe laying is performed with S-lay pipe laying method. Therefore, at the beginning of this thesis Slay method was described, and after that analysis of balance forces was made. Force balance occurs
during pipe laying procedure. Rules of classification societies describe features that such structures
must possess. In this thesis, rules of society Det Norske Veritas were used for analysis of
environmental conditions and loads (DNV-RP-C205), and for characteristics of pipeline (DNV-OSF101). Also API rules were used for designing fixed offshore structures (API RP2A).
Global stinger model was made which was subjected to loads defined according to pipeline laying
scenario at maximum depth. Based on results, areas of greatest stress and critical structural details
were determined. This detail was further analyzed by submodel technique, first level submodel was
made with shell finite elements and second level submodel was made with volume finite elements
including weld geometry. Based on the rules for fatigue calculation of steel offshore structures (DNVRP-C203), an analysis of hot spot stress and stress concentration factor was performed for selected
structural detail. Finally, fatigue life analysis was performed for that structural details subjected to
maximum loading, during stringer assumed life expectancy of 30 years.

• Keywords: rampa za polaganje cjevovoda; S–lay postupak polaganja cjevovoda; strukturni detalji spoja cijevi; zamor materijala; nazivna naprezanja; žarišna naprezanja; faktor koncentracije naprezanja; izvijanje
• Keywords (english): stinger; S–lay pipe laying; structural details of pipe connections; fatigue; nominal stress; hot-spot stress; stress concentration factor – SCF; buckling
• Language: croatian
• URN:NBN: urn:nbn:hr:235:825662
• Study programme: Title: Mechanical Engineering and Naval Architecture - specialist; Study programme type: university; Study level: postgraduate specialist; Academic / professional title: sveučilišni/a specijalist/specijalistica strojarstva i brodogradnje (sveučilišni/a specijalist/specijalistica strojarstva i brodogradnje)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2021-05-27 12:32:22