• 3D FE tool for time dependent settlement predictions 

      Jostad, Hans Petter; Sivasithamparam, Nallathamby; Woldeselassie, B.H.; Lacasse, Suzanne (Chapter, 2016)
      A newly developed calculation tool for fully coupled general 3D finite element consolidation analyses is presented. The development has been part of an ongoing Research and Development project called GeoFuture and the tool ...
    • A macro-element for integrated time domain analyses representing bucket foundations for offshore wind turbines 

      Skau, Kristoffer Skjolden; Grimstad, Gustav; Page, Ana M.; Eiksund, Gudmund Reidar; Jostad, Hans Petter (Journal article; Peer reviewed, 2018)
      The paper presents a macro-element model for bucket foundations to be used in integrated time domain analyses of offshore wind turbines. The macro-element has been formulated in the multi-surface plasticity framework, and ...
    • A macro-element model for multidirectional cyclic lateral loading of monopiles in clay 

      Page, Ana M.; Grimstad, Gustav; Eiksund, Gudmund Reidar; Jostad, Hans Petter (Journal article; Peer reviewed, 2018)
      This paper investigates numerically the impact of multidirectional cyclic loads on the response of a monopile in clay supporting an offshore wind turbine (OWT). The results indicate that multidirectional loading modifies ...
    • A macro-element pile foundation model for integrated analyses of monopilebased offshore wind turbines 

      Page, Ana M.; Grimstad, Gustav; Eiksund, Gudmund Reidar; Jostad, Hans Petter (Journal article; Peer reviewed, 2018)
      The design of OWTs relies on integrated load analyses tools that simulate the response of the entire OWT (including the rotor-nacelle assembly, support structure and foundation) under combined aerodynamic and hydrodynamic ...
    • A New Foundation Model for Integrated Analyses of Monopile-based Offshore Wind Turbines 

      Page, Ana M.; Skau, Kristoffer Skjolden; Jostad, Hans Petter; Eiksund, Gudmund Reidar (Journal article; Peer reviewed, 2017)
      Offshore wind turbines are highly dynamic and tightly coupled systems subjected to variable cyclic loads. Designing and optimizing the support structure is a complex task, where several load scenarios have to be analysed ...
    • A numerical study of capacity and stiffness of circular skirted foundations in clay subjected to combined static and cyclic general loading 

      Skau, Kristoffer Skjolden; Chen, Ying; Jostad, Hans Petter (Journal article; Peer reviewed, 2017)
      Skirted foundations have been widely applied as offshore foundations for several decades. In design, the use of failure envelopes is convenient for assessing stability under combined loading. A large number of studies on ...
    • Alternative Numerical Pile Foundation Models for Integrated Analyses of Monopile-based Offshore Wind Turbines 

      Page, Ana M.; Schafhirt, Sebastian; Eiksund, Gudmund Reidar; Skau, Kristoffer Skjolden; Jostad, Hans Petter; Sturm, Hendrik (Chapter, 2016)
      Lowering the cost for offshore wind energy remains a major challenge. Increasing the accuracy of analysis tools used in the design and optimization process can strengthen the reliability and reduce conservatism, thereby ...
    • An anisotropic shear strength model for cyclic accumulated plastic strain of overconsolidated clay 

      Cai, Fang; Eiksund, Gudmund Reidar; Grimstad, Gustav; Jostad, Hans Petter (Journal article; Peer reviewed, 2014)
      Many geotechnical problems involve calculation of the permanent deformation of overconsolidated clay under undrained cyclic loading. There are many existing methods in the literature which have been made for predicting ...
    • Bucket Foundation in Clay for OWT Subjected to Combined Cyclic Loads 

      Chen, Ying (Master thesis, 2014)
      This thesis project investigates the bucket foundation in clay subjected to cyclic loads. The cyclic irregular loading history in this thesis was represented by the equivalent number of cycles Neq with a certain level of ...
    • Correction factors for undrained LE analyses of sensitive clays 

      Fornes, Petter; Jostad, Hans Petter (Chapter, 2017)
      Correction factors to be used in conventional undrained stability calculations in order to account for post peak strain softening behaviour of sensitive clays, has been recommended based on an extensive sensitivity study ...
    • Creep of geomaterials – some finding from the EU project CREEP 

      Grimstad, Gustav; Karstunen, Minna; Jostad, Hans Petter; Sivasithamparam, Nallathamby; Mehli, Magne; Zwanenburg, Cor; Evert, den Haan; Ghoreishian Amiri, Seyed Ali; Boumezerane, Djamalddine; Kadivar, Mehdi; Haji Ashrafi, Mohammad Ali; Rønningen, Jon A. (Journal article; Peer reviewed, 2017)
      This paper gives a summary of some of the main findings of the EU founded project “Creep of geomaterials”, CREEP. CREEP was an Industry-Academia Partnerships and Pathways (IAPP) project funded from the 7th Framework Programme ...
    • Cyclic Behaviour of Water Saturated Dense Sand 

      Dahl, Birgitte Misund; Løyland, Marit Skaug (Master thesis, 2017)
      Several monotonic and cyclic triaxial tests have been performed at NGI in association with the ongoing strategic project, SP9. The test material is dense saturated sand from the Siri offshore field in the North Sea, and ...
    • Finite Element Analyses of Spudcan Penetration Using CEL Method 

      Worren, Aleksander (Master thesis, 2013)
      A hazard during installation of jack-up spudcans is punch-through, which is characterized by a peak resistance, followed by a significant reduction in spudcan resistance. This might lead to an uncontrolled rapid leg ...
    • Finite Element Analysis of Suction Bucket Foundations in Sand Subjected to Cyclic Loading 

      Jahren, Ingerid Elisabeth Rolstad (Master thesis, 2018)
      A suction bucket or suction caisson is a foundation concept for supporting offshore installations. The practical experience related to this concept is mainly based on applications in the oil and gas industry. Observations ...
    • Modelling of skirted foundations for offshore wind turbines 

      Skau, Kristoffer Skjolden (Doctoral theses at NTNU;2018:140, Doctoral thesis, 2018)
      The thesis focuses on the modelling of the response of shallow skirted foundations supporting offshore wind turbines (OWT). OWT-structures need to be optimized in design to reduce the cost of energy from offshore wind ...
    • Modelling of soil-structure-interaction for flexible caissons for offshore wind turbines 

      Skau, Kristoffer Skjolden; Jostad, Hans Petter; Eiksund, Gudmund Reidar; Sturm, Hendrik (Journal article; Peer reviewed, 2018)
      Published foundation models and procedures for calculation of caisson foundation response typically assume a rigid caisson in deformable soil. However, recent published measurement data from a prototype suction bucket ...
    • Monopile Foundation Models for Dynamic Structural Analyses of Offshore Wind Turbines 

      Risueño, Ana María Page (Doctoral theses at NTNU;2018:363, Doctoral thesis, 2018)
      Offshore wind energy plays an important role in sustainability-focused international policies and experiences one of the fastest growth rates of all renewable energy sources. Although the cost of offshore wind energy has ...
    • REDWIN – REDucing cost in offshore WINd by integrated structural and geotechnical design 

      Skau, Kristoffer Skjolden; Page, Ana M.; Kaynia, Amir M.; Løvholt, Finn; Norén-Cosgriff, Karin; Sturm, Hendrik; Andersen, H.S.; Nygaard, Tor Anders; Jostad, Hans Petter; Eiksund, Gudmund Reidar; Havmøller, O.; Strøm, P.; Eichler, D. (Journal article; Peer reviewed, 2018)
      The cost of offshore wind energy production has to be reduced continuously to improve its competitiveness compared to other energy sources. To contribute to this goal, a 4- year research project REDWIN – REDucing cost of ...
    • Stabilitetsanalyser ved hjelp av elementmetoden i GeoSuite 

      Bjørklimark, Jonas Graneggen; Blindheim, Tore Landsverk (Master thesis, 2018)
      Skråningsstabilitet er en av mange viktige problemstillinger innen geoteknisk prosjektering og behovet for gode analysemetoder og -verktøy er derfor tilstede. Gjennom prosjektet GeoFuture har NGI (Norges Geotekniske ...
    • Undrained Lateral Soil Response of Offshore Monopiles in Layered Soil 

      Granås, Jonas Løken (Master thesis, 2016)
      Finite Element analyses (FEA) may give coupling between soil layers with different properties when it comes to lateral response of an offshore monopile. The common design recommendation API Recommended Practice (API-RP), ...