Lecture Notes for Engineering 5003 – Ship Structures I

Ships and Offshore Structures, 2010

2018

The course is intended to develop the student’s knowledge of ship structures. The focus is on various types of intact structural behavior, building upon concepts from mechanics of materials and statics. Changes to 2018 edition: • Updated Topic 1 – with ship structural features included • Updated Topic 2 – new discussion of approach to structural design • New Topic 11 – discussion of use of tables and superposition • New beam tables in Appendix 4 • Energy Methods moved to Appendix 7

The course is intended to develop “advanced” knowledge of structures. The particular focus is on various types of structural failure in ships. Many of the topics presented in these lectures are the subject of ongoing research.

2011

Australian journal of mechanical engineering, 2007

Nowadays, the larger fl exibility of ship structures, as well as wave-load spectra shifted to higher frequencies due to high-speed operating regimes, allow the onset of signifi cant vibration phenomena. Recently, there has been increasing interest in combining seakeeping with vibration tests that may result in a deeper physical insight into this topic. In fact, experimental investigations on physical scaled models may benefi t general purpose techniques for structural dynamic analysis in order to provide an interesting point of view of the hull vibration problem. The application of methods for modal identifi cation, such as the Output-Only techniques, fi ts the present identifi cation problem, particularly, where the main source of excitation for the structure is the ambient excitation due to the sea waves. In this paper, the tests carried out in a towing tank basin with an elastically scaled and segmented model are analysed in order to investigate the bending response, ie. bending vibrations modes (shape, frequency and damping) and whipping oscillations. The modal parameters of the "dry" and "wet" modes of the elastic segmented model are identifi ed with the Output-Only technique, based on the Frequency Domain Decomposition. Then, the ship response is analysed in terms of response amplitude operators and recorded time-histories. The correspondence with the full-scale ship, and the dependence of the aforementioned estimations with respect to the forward speed, are highlighted in the paper.

Ocean Engineering, 2017

This work is focused on experimental investigation of the hull girder loads on an intact and damaged naval ship DTMB 5415 at zero speed. The experimental campaign was carried out in head and beam regular waves at the University of Strathclyde. The effect of the use of moorings in the model experimental setup was investigated in the context of loads assessment, and the moorings are shown to influence the measured hull girder loads at some wave frequency compared to the free drift case. Therefore the tests in beam seas are performed with free drifting model while the moored model setup was adopted for head seas. The results for ship motions are compared with those from a previous campaign giving an insight into repeatability and uncertainty of measurements. The roll decay of the ship in both intact and damaged conditions is analysed and the linear and quadratic extinction coefficients for the model and the ship scale are reported and detailed discussion on intact-versus-damaged ship roll damping behaviour is given. The results for the hull girder loads are presented for intact and damaged ship. An investigation of the nonlinear effects due to wave height variation in the range wave height to wave length from 1/50 to 1/22 on shear force and bending moment was carried out for a range of wave lengths to ship length ratios from 0.8 to 1.4. The results of the extensive campaign are compared against similar experimental studies forming a benchmark for validation of numerical methods. Keywords: 5415 DTMB model, wave loads on intact and damaged ship; nonlinear responses; experimental shear force and bending moments assessment, roll decay, equivalent linear roll extinction coefficient NOMENCLATURE A -wave amplitude, m B OA -beam over all, m B WL -beam at waterline, m C B -block coefficient C M -midship section coefficient C P -prismatic coefficient D -depth, m g -acceleration of gravity, 9.80665 m/s 2 GM -transversal metacentric height, m H -wave height, m HBM -horizontal bending moment, Nm HSF -horizontal shear force, N H/λ W -ratio between wave height and wave length k -wave number, 2π/λ W KG -vertical position of the centre of gravity, from BL, m KM -vertical position of the metacentre, from BL, m k XX -radius of gyration with respect to x axis, m,

1995

The SHIP STRUCTURE COMMllTEE is constituted to prosecute a research program to improve the hull structures of ships and other marine structures by an extension of knowledge pertaining to design, materials, and methds of construction. RADM J. C. Card, USCG (Chairman)

2018

We herein propose a new design procedure of a flexible container ship model where the vertical bending and torsional vibration modes are similar to its prototype. To achieve similarity in torsional vibration mode shapes, the height of the shear center of the model must be located below the bottom hull, similar to an actual container ship with large opening decks. Therefore, we designed a ship model by imparting appropriate stiffness to the hull, using urethane foam without a backbone. We built a container ship model according to this design strategy and validated its dynamic elastic properties using a decay test. We measured wave-induced structural vibrations and present the results of tank experiments in regular and freak waves.