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A lightweight ice going hull concept for freshwater ice operations
KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Lättkonstruktioner, marina system, flyg- och rymdteknik, rörelsemekanik. (Naval Architecture)ORCID iD: 0000-0003-3160-9575
KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.ORCID iD: 0000-0003-4180-4710
KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics.ORCID iD: 0000-0002-1187-4796
KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics.ORCID iD: 0000-0002-9110-9401
(English)Manuscript (preprint) (Other academic)
Abstract [en]

A fundamental challenge in ice-prone waterborne public transportation systems is the need for ice-strengthening while being fuel efficient during ice-free periods. To achieve this, the use of lightweight hull structures is explored in the current study by starting with introducing a tri-layer structural concept for an ice going hull. The three layers correspond to abrasion loads, impact loads and pressure loads experienced during a typical ice-hull interaction. Several structural concepts suited towards these respective loading mechanisms are considered. Most favorable parametric variants are identified and assembled as contenders in the tri-layer concept. The assembly is tested against experimentally validated ice impact models in FEA as well as a realistic quasi-static pressure representation. Three different lightweight structural concepts including aluminum grillage, stiffened sandwich structure and metal-FRP stiffened sandwich structure are compared and discussed. It is found that the latter of the three concepts is suited best towards both quasi-static and impact loading. Ice going ferries built with ice strengthened lightweight hulls can reduce emissions, fuel consumption as well as increase the payload capacity. Such a ferry would be competitive with non-ice going ferries during ice free periods.

Keywords [en]
Sandwich structure, ice impact model, FEM, LS Dyna, lightweight hull, waterborne urban mobility, composites, Metal grillage, Aluminium alloy, Titanium alloy
National Category
Marine Engineering Vehicle Engineering
Research subject
Vehicle and Maritime Engineering
Identifiers
URN: urn:nbn:se:kth:diva-317395OAI: oai:DiVA.org:kth-317395DiVA, id: diva2:1694565
Funder
Swedish Transport Administration, TRV 2018/6471
Note

QC 20220912

Available from: 2022-09-09 Created: 2022-09-09 Last updated: 2022-09-12Bibliographically approved
In thesis
1. Framework for holistic design of ferries focusing on lightweight ice going hulls.
Open this publication in new window or tab >>Framework for holistic design of ferries focusing on lightweight ice going hulls.
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Waterborne public transportation (WPT) is slowly increasing in importance as an active component of public transportation networks in cities. City planners are looking at WPT to overcome urban congestion and pollution. However, prevalent challenges like ferry procurement, poor state of existing ferry fleets and technical challenges like the presence of ice, have created reluctance in the minds of public transport providers (PTPs).  While contemporary research shows ferries can be economical and environmentally friendly, there are some fundamental challenges that need to be addressed before PTPs can feel confident.

In this regard, deterrents from PTP’s perspective are identified and solutions are investigated, starting with a systematic characterization of WPT. A definite structure for operational requirements is proposed in an objective manner. Using these as basis, two standard ferry sizes that could fulfil multiple WPT roles in majority of cities are introduced. For establishing city-wise tailoring, platform-architecture based modularization of ferries is proposed. The ferry modules are tailored with respect to operational requirements in a clear and objective manner through the introduction of an evaluation methodology. The method incorporates economic, social, environmental, and regulatory stakeholders. These proposed solutions are aimed at improving PTP’s confidence in WPT and provides solutions for the marine industry to produce quick, cost efficient and tailored ferries. 

Next, the scope is focused towards investigating sustainable operations in freshwater ice conditions, typically found in the Stockholm region in Sweden. The ice going ferries today operate with ice strengthened heavy hulls. While they work well in ice, they perform poorly in comparison with non-ice going ferries during ice free months. Correspondingly, solutions towards lightweight ice going hulls are investigated. 

This investigation starts with understanding ice-hull interaction mechanisms. Then, techniques to estimate the ice loads are investigated. We adopt a probabilistic approach to tackle the limitations due to the stochastic nature of ice and a lack of experimental data. The resulting load cases are used for evaluating lightweight structural concepts. 

The investigation is approached by dividing ice-hull interaction into quasi-static, dynamic and abrasive loading phases. Several candidates corresponding to the first two loading phases are investigated parametrically. The range of structural concepts include metal grillages, bio-inspired composites, and sandwich structures. Realistic loading models for quasi-static and impact mechanisms are developed and validated with experiments. The winning candidates for each loading phase are combined to propose a tri-layer lightweight structural concept. Three candidates for the concept are evaluated and compared.

The thesis answers several questions that riddle WPT today. But at the same time, it raises new questions. Several directions for future work are identified. With continued development, it would be possible to see modularly tailored ferries operating with lightweight hulls in WPT systems around the world.

Abstract [sv]

Vattenburen kollektivtrafik ökar i betydelse som en aktiv komponent i kollektivtrafiknätverk i städer. När trängsel och föroreningar ökar i städerna, börjar stadsplanerare se på vattenvägarna. Men utmaningar när det gäller färjeanskaffning, nergångna befintliga färjeflottor och tekniska utmaningar som is på vintern, har skapat motvilja hos kollektivtrafikleverantörer. Forskning visar att färjor kan vara både ekonomiska och miljövänliga. Inte desto mindre finns det grundläggande utmaningar som måste hanteras innan kollektivtrafikleverantörerna känner tillförsikt. För att möta detta identifieras de avskräckande utmaningarna och lösningar undersöks inledningsvis med att systematiskt karakterisera den vattenburna kollektivtrafiken. En bestämd struktur för verksamhetskrav föreslås med objektiva mått. Med dessa som grund introduceras två standardfärjestorlekar som skulle kunna fylla flera transportroller i städer med vattenvägar. För att möjliggöra skräddarsydda lösningar i olika städer, etableras en mudulariserad plattformsarkitektur för färjorna. Färjemodulerna skräddarsys med hänsyn till operativa krav och granskas objektivt med hjälp av en utvecklad utvärderingsmetodik. Metoden omfattar ekonomiska, sociala, miljömässiga och regelverksaspekter. Metodiken syftar till att förbättra kollektivtrafikleverantörernas förtroende för vattenburen kollektivtrafik och föreslår också lösningar för den marina industrin för snabb produktion av kostnadseffektiva, skräddarsydda färjor.

I nästa steg studeras frågan om hållbar sjötrafik vintertid. Fokus är sötvattenis typisk för Stockholmsregionen i Sverige. De isgående färjorna i trafik idag har isförstärkta tunga skrov. Även om det fungerar bra när det är is, presterar de dåligt i jämförelse med icke-isgående färjor under de isfria månaderna. Detta motiverar utveckling av lätta isgående färjor. Undersökningen inleds med studier av interaktionsmekanismerna mellan is och skrov. Därefter undersöks metoder för att uppskatta isbelastningarna. Här hanteras flera begränsningar, kopplade till brist på experimentell data och isens stokastiska natur, med hjälp av en probabilistisk metod. Metoden tillämpas för att generera designlastfall för undersökning av olika lätta konstruktionskoncept. Undersökningen delar upp is-skrovinteraktionen i kvasistatiska, dynamiska och abrasiva belastningsfaser. Flera kandidater för de två första faserna undersöks parametriskt. Valet av strukturkoncept omfattar metallstrukturer, komposit- och sandwichstrukturer. De är valda utifrån nuvarande designpraxis och med varianter inspirerade från naturen. Realistiska modeller för kvasistatiska- och stötbelastningar utvecklas och valideras med experimentdata. De bästa strukturvarianterna för respektive belastningsfas kombineras till förslag av lättviktskonstruktion i tre lager. Tre sådana strukturvarianter utvärderas och jämförs.

Avhandlingen svarar på flera frågor som idag hämmar vattenburen kollektivtrafik. Den väcker samtidigt nya frågor och flera riktningar för framtida studier identifieras. Slutsatserna belyser möjligheten för modulärt skräddarsydda färjor med lättviktsskrov att operera i den vattenburna kollektivtrafiken runt om i världen.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2022. p. 101
Series
TRITA-SCI-FOU ; 2022:45
Keywords
waterborne public transportation, commuter ferry, modular design, platform architecture, operational requirements, sustainable performance index, ice-hull interaction, lightweight ice-going hulls, composite, sandwich structure, ice impact model.
National Category
Vehicle Engineering Transport Systems and Logistics Marine Engineering Energy Systems
Research subject
Vehicle and Maritime Engineering
Identifiers
urn:nbn:se:kth:diva-317413 (URN)978-91-8040-341-2 (ISBN)
Public defence
2022-09-29, https://kth-se.zoom.us/webinar/register/WN_fLrJ2yFNToKYcqiqoYUqCQ, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Transport Administration, TRV 2018/6471Region Stockholm
Available from: 2022-09-12 Created: 2022-09-09 Last updated: 2022-09-20Bibliographically approved

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Cheemakurthy, HarshaBarsoum, ZuheirBurman, MagnusGarme, Karl

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