The Experts below are selected from a list of 219 Experts worldwide ranked by ideXlab platform

Antonini A. - One of the best experts on this subject based on the ideXlab platform.

  • Wolf Rock lighthouse: Past developments and future survivability under wave loading
    'The Royal Society', 2019
    Co-Authors: Raby A. C., Antonini A., Pappas A., Dassanayake D. T., Ownjoh J. M.w., D'ayala D.
    Abstract:

    Lighthouses situated on exposed rocky outcrops warn mariners of the dangers that lurk beneath the waves. They were first constructed when approaches to wave loading and structural response were relatively unsophisticated, essentially learning from previous failures. Here, we chart the evolution of lighthouses on the Wolf Rock, situated between Land's End and the Isles of Scilly in the UK. The first empirical approaches are described, followed by design aspects of the present tower, informed by innovations developed on other rocky outcrops. We focus on a particular development associated with the automation of lighthouses: the helideck platform. The design concept is described and the structure then scrutinized for future survivability, using the latest structural modelling techniques of the entire lighthouse and helideck. Model validation data were obtained through a complex logistical field operation and experimental modal analysis. Extreme wave loading for the model required the identification of the 250-year return period wave using a Bayesian method with informative prior distributions, for two different scenarios (2017 and 2067). The structural models predict responses of the helideck to wave loading which is characterized by differential displacements of 0.093m (2017) and 0.115m (2067) with associated high tension forces and plastic strain.Coastal Engineerin

  • Bayesian oma of offshore rock lighthouses: Surprises with close modes, symmetry and alignment
    International Operational Modal Analysis Conference (IOMAC), 2019
    Co-Authors: Ownjoh James, Raby Aliso, Au, Siu Kui, Zhu Zuo, Wang Xinrui, Antonini A.
    Abstract:

    A set of seven rock lighthouses around the British Isles was studied by a combination of forced and ambient vibration tests executed with some extreme logistical constraints. Forced vibration testing of the circular section masonry towers combined with experimental modal analysis identified modes with alignment assumed the same as the shaker as well as some interesting effects of helideck retrofit, whereas operational modal analysis revealed the considerable degree of uncertainty in mode shape alignment. Hence Bayesian operational modal analysis was used to characterise the uncertainty and find the best representation of mode shape direction. While perfectly axisymmetric towers would show a single frequency omnidirectional mode, OMA reveals the split modes and allows un unbiased view of directionality. The variability and uncertainty of these mode shape directions are further revealed using Bayesian OMA.Accepted Author ManuscriptCoastal Engineerin

  • Experimental modal analysis of British rock lighthouses
    'Elsevier BV', 2018
    Co-Authors: Ownjoh Jmw, Antonini A., Raby A, Assi J, Hudso E, Dobso P
    Abstract:

    No embargo required.© 2018 The Authors Iconic lighthouses constructed on offshore reefs around the British Isles in the 19th century continue to play a crucial role in safe navigation, but the longevity of these historical structures is threatened by extreme weather. A program of experimental dynamic investigations has been carried out to support characterisation of extreme impulsive breaking wave loads on these structures, using monitored response data. This paper describes the procedures and outcomes of this program, which included modal tests of a collection of six of these lighthouses between June 2016 and October 2017. Five of the six lighthouses tested (Les Hanois, Wolf Rock, Longships, Bishop Rock and Eddystone) feature a 20th century metal helideck atop a 19th century masonry tower, with a Scottish lighthouse (Dubh Artach) being the exception that provides baseline behaviour of a relatively simple tower. All the masonry towers are imperfectly axisymmetric to some degree and all present logistical challenges for experimental work as they can only be accessed by helicopter flights subject to severe weather and time constraints. Against such challenges it was possible to identify key modal parameters, and to highlight some interesting effects due to symmetry and helideck retrofit. Notable findings were that most important modes have frequencies ranging between 4 Hz and 7 Hz and modal masses as low as ∼200 t. The rarely investigated effect of imperfect axisymmetry on forced vibration testing is studied, along with the introduction of additional modes due to retrofitted helideck. The implications of these effects on experimental modal analysis from forced vibration test data is illustrated. Finally, accelerations recorded on Wolf Rock Lighthouse during the 2017–2018 winter storm season show the modal test data can be used to infer breaking wave modal impulses up to 8 kNs

Hyun Soo Shin - One of the best experts on this subject based on the ideXlab platform.

  • Full Stochastic Fatigue Analysis for Kizomba ‘A’ FPSO-Hull Interface Design
    Volume 1: Offshore Technology; Ocean Space Utilization, 2003
    Co-Authors: Jeong Heon Na, Hyun Soo Shin
    Abstract:

    As the offshore oilfields shift into the deeper ocean of less infra, FPSOs become a popular solution. Many FPSOs operate in fields where they are expected to stay for decades without drydocking for maintenance. Currently one of the most active area of the FPSO installation is the west Africa offshore where the sea state is benign and the swell from the south is dominant and the water depth is deep. In the case of long operation in the benign site, the fatigue is rather important in the structural design point of view. This paper describes the first extensive practical application of the full stochastic fatigue analysis method to the design of the FPSO-hull interface design like topside supports, flare tower foundation, riser porches, caissons, crane pedestals, mooring foundations, helideck connections, deck penetrations and etc. Especially, topside support is highlighted in detail because of its potential inertia loading due to heavy weight and importance in fabrication stage. The full length of Kizomba ‘A’ FPSO being built in Hyundai Heavy Industries is modeled for the global analysis and the boundary conditions from the global model analysis are transferred for the local model analysis. Some discussions of screening analysis and hot spot stress calculation and roll damping evaluation are also presented.© 2003 ASME

  • full stochastic fatigue analysis for kizomba a fpso hull interface design
    ASME 2003 22nd International Conference on Offshore Mechanics and Arctic Engineering, 2003
    Co-Authors: Jeong Heon Na, Hyun Soo Shin
    Abstract:

    As the offshore oilfields shift into the deeper ocean of less infra, FPSOs become a popular solution. Many FPSOs operate in fields where they are expected to stay for decades without drydocking for maintenance. Currently one of the most active area of the FPSO installation is the west Africa offshore where the sea state is benign and the swell from the south is dominant and the water depth is deep. In the case of long operation in the benign site, the fatigue is rather important in the structural design point of view. This paper describes the first extensive practical application of the full stochastic fatigue analysis method to the design of the FPSO-hull interface design like topside supports, flare tower foundation, riser porches, caissons, crane pedestals, mooring foundations, helideck connections, deck penetrations and etc. Especially, topside support is highlighted in detail because of its potential inertia loading due to heavy weight and importance in fabrication stage. The full length of Kizomba ‘A’ FPSO being built in Hyundai Heavy Industries is modeled for the global analysis and the boundary conditions from the global model analysis are transferred for the local model analysis. Some discussions of screening analysis and hot spot stress calculation and roll damping evaluation are also presented.© 2003 ASME

Alessandro Antonini - One of the best experts on this subject based on the ideXlab platform.

  • bayesian oma of offshore rock lighthouses surprises with close modes symmetry and alignment
    2019
    Co-Authors: James M W Ownjoh, Aliso Raby, Zuo Zhu, Xinrui Wang, Alessandro Antonini
    Abstract:

    A set of seven rock lighthouses around the British Isles was studied by a combination of forced and ambient vibration tests executed with some extreme logistical constraints. Forced vibration testing of the circular section masonry towers combined with experimental modal analysis identified modes with alignment assumed the same as the shaker as well as some interesting effects of helideck retrofit, whereas operational modal analysis revealed the considerable degree of uncertainty in mode shape alignment. Hence Bayesian operational modal analysis was used to characterise the uncertainty and find the best representation of mode shape direction. While perfectly axisymmetric towers would show a single frequency omnidirectional mode, OMA reveals the split modes and allows un unbiased view of directionality. The variability and uncertainty of these mode shape directions are further revealed using Bayesian OMA.

  • experimental modal analysis of british rock lighthouses
    Marine Structures, 2018
    Co-Authors: James M W Ownjoh, Aliso Raby, James Assi, Emma Hudso, Alessandro Antonini, Pete Dobso
    Abstract:

    Abstract Iconic lighthouses constructed on offshore reefs around the British Isles in the 19th century continue to play a crucial role in safe navigation, but the longevity of these historical structures is threatened by extreme weather. A program of experimental dynamic investigations has been carried out to support characterisation of extreme impulsive breaking wave loads on these structures, using monitored response data. This paper describes the procedures and outcomes of this program, which included modal tests of a collection of six of these lighthouses between June 2016 and October 2017. Five of the six lighthouses tested (Les Hanois, Wolf Rock, Longships, Bishop Rock and Eddystone) feature a 20th century metal helideck atop a 19th century masonry tower, with a Scottish lighthouse (Dubh Artach) being the exception that provides baseline behaviour of a relatively simple tower. All the masonry towers are imperfectly axisymmetric to some degree and all present logistical challenges for experimental work as they can only be accessed by helicopter flights subject to severe weather and time constraints. Against such challenges it was possible to identify key modal parameters, and to highlight some interesting effects due to symmetry and helideck retrofit. Notable findings were that most important modes have frequencies ranging between 4 Hz and 7 Hz and modal masses as low as ∼200 t. The rarely investigated effect of imperfect axisymmetry on forced vibration testing is studied, along with the introduction of additional modes due to retrofitted helideck. The implications of these effects on experimental modal analysis from forced vibration test data is illustrated. Finally, accelerations recorded on Wolf Rock Lighthouse during the 2017–2018 winter storm season show the modal test data can be used to infer breaking wave modal impulses up to 8 kNs.

James M W Ownjoh - One of the best experts on this subject based on the ideXlab platform.

  • bayesian oma of offshore rock lighthouses surprises with close modes symmetry and alignment
    2019
    Co-Authors: James M W Ownjoh, Aliso Raby, Zuo Zhu, Xinrui Wang, Alessandro Antonini
    Abstract:

    A set of seven rock lighthouses around the British Isles was studied by a combination of forced and ambient vibration tests executed with some extreme logistical constraints. Forced vibration testing of the circular section masonry towers combined with experimental modal analysis identified modes with alignment assumed the same as the shaker as well as some interesting effects of helideck retrofit, whereas operational modal analysis revealed the considerable degree of uncertainty in mode shape alignment. Hence Bayesian operational modal analysis was used to characterise the uncertainty and find the best representation of mode shape direction. While perfectly axisymmetric towers would show a single frequency omnidirectional mode, OMA reveals the split modes and allows un unbiased view of directionality. The variability and uncertainty of these mode shape directions are further revealed using Bayesian OMA.

  • experimental modal analysis of british rock lighthouses
    Marine Structures, 2018
    Co-Authors: James M W Ownjoh, Aliso Raby, James Assi, Emma Hudso, Alessandro Antonini, Pete Dobso
    Abstract:

    Abstract Iconic lighthouses constructed on offshore reefs around the British Isles in the 19th century continue to play a crucial role in safe navigation, but the longevity of these historical structures is threatened by extreme weather. A program of experimental dynamic investigations has been carried out to support characterisation of extreme impulsive breaking wave loads on these structures, using monitored response data. This paper describes the procedures and outcomes of this program, which included modal tests of a collection of six of these lighthouses between June 2016 and October 2017. Five of the six lighthouses tested (Les Hanois, Wolf Rock, Longships, Bishop Rock and Eddystone) feature a 20th century metal helideck atop a 19th century masonry tower, with a Scottish lighthouse (Dubh Artach) being the exception that provides baseline behaviour of a relatively simple tower. All the masonry towers are imperfectly axisymmetric to some degree and all present logistical challenges for experimental work as they can only be accessed by helicopter flights subject to severe weather and time constraints. Against such challenges it was possible to identify key modal parameters, and to highlight some interesting effects due to symmetry and helideck retrofit. Notable findings were that most important modes have frequencies ranging between 4 Hz and 7 Hz and modal masses as low as ∼200 t. The rarely investigated effect of imperfect axisymmetry on forced vibration testing is studied, along with the introduction of additional modes due to retrofitted helideck. The implications of these effects on experimental modal analysis from forced vibration test data is illustrated. Finally, accelerations recorded on Wolf Rock Lighthouse during the 2017–2018 winter storm season show the modal test data can be used to infer breaking wave modal impulses up to 8 kNs.

Jeong Heon Na - One of the best experts on this subject based on the ideXlab platform.

  • Full Stochastic Fatigue Analysis for Kizomba ‘A’ FPSO-Hull Interface Design
    Volume 1: Offshore Technology; Ocean Space Utilization, 2003
    Co-Authors: Jeong Heon Na, Hyun Soo Shin
    Abstract:

    As the offshore oilfields shift into the deeper ocean of less infra, FPSOs become a popular solution. Many FPSOs operate in fields where they are expected to stay for decades without drydocking for maintenance. Currently one of the most active area of the FPSO installation is the west Africa offshore where the sea state is benign and the swell from the south is dominant and the water depth is deep. In the case of long operation in the benign site, the fatigue is rather important in the structural design point of view. This paper describes the first extensive practical application of the full stochastic fatigue analysis method to the design of the FPSO-hull interface design like topside supports, flare tower foundation, riser porches, caissons, crane pedestals, mooring foundations, helideck connections, deck penetrations and etc. Especially, topside support is highlighted in detail because of its potential inertia loading due to heavy weight and importance in fabrication stage. The full length of Kizomba ‘A’ FPSO being built in Hyundai Heavy Industries is modeled for the global analysis and the boundary conditions from the global model analysis are transferred for the local model analysis. Some discussions of screening analysis and hot spot stress calculation and roll damping evaluation are also presented.© 2003 ASME

  • full stochastic fatigue analysis for kizomba a fpso hull interface design
    ASME 2003 22nd International Conference on Offshore Mechanics and Arctic Engineering, 2003
    Co-Authors: Jeong Heon Na, Hyun Soo Shin
    Abstract:

    As the offshore oilfields shift into the deeper ocean of less infra, FPSOs become a popular solution. Many FPSOs operate in fields where they are expected to stay for decades without drydocking for maintenance. Currently one of the most active area of the FPSO installation is the west Africa offshore where the sea state is benign and the swell from the south is dominant and the water depth is deep. In the case of long operation in the benign site, the fatigue is rather important in the structural design point of view. This paper describes the first extensive practical application of the full stochastic fatigue analysis method to the design of the FPSO-hull interface design like topside supports, flare tower foundation, riser porches, caissons, crane pedestals, mooring foundations, helideck connections, deck penetrations and etc. Especially, topside support is highlighted in detail because of its potential inertia loading due to heavy weight and importance in fabrication stage. The full length of Kizomba ‘A’ FPSO being built in Hyundai Heavy Industries is modeled for the global analysis and the boundary conditions from the global model analysis are transferred for the local model analysis. Some discussions of screening analysis and hot spot stress calculation and roll damping evaluation are also presented.© 2003 ASME