One of the main causes of the collapse of “Tensyudai”, base of castle tower, of Japanese castles is the inertia of the masonry wall stones during the earthquake. The purpose of this study is to ...evaluate collapse acceleration when horizontal acceleration acts on the masonry walls. Inclining experiments of masonry wall models are conducted to statically represent the horizontal load, and the collapse mechanism is discussed. The collapse mechanism of the masonry walls is constructed considering the three-dimensional mechanical characteristics under horizontal loading as inertia force due to horizontal ground motion acceleration, and the critical states equations is derived. It is confirmed that there is good correspondence between experimental and theoretical collapse accelerations.
The classical method of inclining experiments has been used to determine the position of the ship's vertical center of gravity for many years. The method contains some basic assumptions, which is why ...the accuracy of the method has been debated in the last few years. Modern ships often have chines, or pronounced flare at fore and aft extremities, that can lead to a significant change in the waterline. The position of the metacenter changes on these ships as they incline. Therefore, the calculation of the ship's center of gravity by the classical method may be inaccurate.
In this paper, three different methods that are not based on the assumption of an unchanged metacenter are examined. Using a graphical, polar, and general method, the position of the ship's center of gravity system can be determined for any ship without determining the position of the metacenter. The three methods mentioned in this paper were observed and tested on four different ships. In addition, the results of the classical method are compared with the results obtained from recently developed methods
It is a well-known fact that the current method for calculating a ship's vertical centre of gravity (VCG) following inclining experiments is limited when considering magnitude of applied heel angle ...and accuracy achieved for certain hull-forms due to the assumption of unchanged metacentre position when the vessel is heeled. New methods for calculating the VCG have been proposed, notably the Generalised and the Graphical methods. This paper aims to test these methods on a range of vessels, as well as present and contrast a new method named, the Polar method. The test will establish the error potential for each method using a purely technical software-simulated inclining experiment. Using the established error potential, a corrected VCG is calculated from actual inclining VCG values, which have been evaluated against the loading conditions for each vessel to see if the stability margins have been compromised. The study confirms the Classical method's dependency on applied heel angle magnitude, the change in waterplane area and that it compromises safety in some cases. The other methods, especially the Generalised and the Polar, produce very accurate results for any floating position of the vessel, highlighting the need to tear down the wall-sided assumption implicit in the Classical method and replace it with the better and more flexible methods.
•Inclining experiment calculation methods tested on a range of vessels.•A technical software-simulated inclining experiment has been applied.•Using established error potentials, actual VCG values validity has been assessed.•New, Polar method, for calculating VCG following inclining experiment presented.•Newly proposed methods show better accuracy and flexibility than the Classical method.
The inclining experiment is typically performed for all new-build ships and after any major refit. The purpose of the inclining experiment is to establish the vertical distance of the centre-of-mass ...of the ship above its keel in the lightship condition. This value is then taken as the point of reference when loading the ship, for establishing the ‘in-service’ stability, throughout the life of the ship. Experimental uncertainty analysis is commonly utilised in hydrodynamic testing to establish the uncertainty in a result as a function of the input variables. This can in turn be utilised to establish an interval about the result that may be expected to encompass a large fraction of the distribution of values that could reasonably be attributed to the measurement. This paper provides a methodology for calculating a confidence interval for the location of the centre-of-mass of a ship from an inclining experiment; and ultimately, in any load condition.
The uncertainty compared to an assumed metacentric height of 0.15m is provided for four classes of ship: buoy tender 0.15±0.15m (±100%); super yacht 0.150±0.033m (±22.0%); supply ship 0.150±0.047m (±31.3%), container ship 0.150±0.029m (±19.3%), ropax 0.150±0.077m (±100%).
•Procedure for evaluating and reducing uncertainty in the inclining experiment.•For some ships, a substantial increase in the minimumGM¯ may be necessary.•A complete procedure for establishing the uncertainty in GM¯ for any load condition.
The stability of a ship is the most important safety criteria to be considered during the design process, in fact an error in the design of the hull. An error in the stability evaluation has two ...different levels of danger, each one related to the other: the loss of stability leads to the loss of the ship, and this loss usually happens suddenly and quickly, causing a serious danger for the passengers. At the same time, in last decades, yachts have been changing significantly, increasing their dimensions from “boat” to “ships”, and the Rules have followed this change setting different criteria to be met. This has led to a different approach to motor yacht design, and to the way of building yachts, considering new materials, manufacturing, etc. For a designer ‘managing the stability of a yacht’ is the capability to have control over the trim and heel when an inclining cause occurs. This capability is strictly related to the hull shape and the weight distribution in three-dimensional space; the criteria of stability for motor yachts have been raising especially in last 2 decades, becoming more and more strict, but this request has to fight with the development of the market and the design that requests always larger superstructures, creating a serious conflict for the naval architects. Considering the importance of stability, undoubtedly considered as mandatory, we can underline the relevance of a method for an immediate evaluation of the parameters involved, especially at the beginning of the project, in order to foresee the stability of a motor yacht and operate in an interactive way with the production department. The suggested method aims at filling a void in the available documentation, referring to a methodology already known and used in Naval Architecture for the evaluation of the residual resistance of the various hulls, with the creation of a systematic database, but this methodology has net yet been applied to stability. The search for the stability parameters is usually done applying a direct weight estimation, considering the weight of each items, like shell plates, girders, single machinery etc. and the position of the center of gravity and then, once, estimated the center of gravity of the ship, verify if the stability criteria are satisfied. But the interactivity concept contained in the proposal is to have already a target to aim, in terms of position of center of gravity G, and constantly adjusting the distribution of each item to come close to that value, similarly to the already mentioned method to aim at values of geometrical parameters regarding the resistance. The present work, in order to provide this method for the stability, will examine a series of various motor yachts, with their inclining experiment and data, in order to create a methodological criteria to foresee the performances in terms of stability and the main design criteria that can be adopted. The method will give values and tendencies of main stability parameters to be aimed before starting the project, without having to follow the complete process of a preliminary calculation, with an important saving of time.
Ships should ensure safe navigation by meeting the stability norms defined by the International Maritime Organization (IMO) and determined by national maritime administrations. The fulfillment of ...these norms is becoming increasingly important, especially for passenger ships used for tourist excursions. Recently, the development of maritime tourism has greatly increased the demand for these ships most of which are converted fishing vessels. The situation described in this paper pertains to Albania and most probably differs in other countries in the region and the wider area. Ships rarely have adequate technical documentation. The Albanian Register of Shipping requires the performance of stability tests, the results of which are entered in the amended stability book to ensure the vessels’ compliance with the norms following modifications undergone and guarantee safe navigation for tourists. An examination of a variety of ship design papers helped us identify various methods and methodologies for determining approximate geometric ship elements with an acceptable degree of reliability. However, their use should be limited and reliability proven by calculating parameters such as lightship VCG, number of passengers per m2, assessing the possible range and area of navigation and weather conditions (mainly wind speed and wave forces). The calculations based on stability testing and the use of highly reliable software such as MaxSurf - Integrated Naval Architecture Software, Napa - Naval Architectural Package Autoship - Systems Operation, Orca3D – Naval Architecture Software delivered fast and reliable stability assessment results and verified conformance with the norms prescribed by the Albanian Register of Shipping.
Stability and trim calculations require the knowledge of the displacement and of the position of the centre of gravity. To calculate these quantities it is necessary to organize the ship masses into ...weight groups. The sum of the weight groups that do not change during operation is called lightship. The sum of the masses that change from a load case to another is called deadweight. The sum of lightship and deadweight is the displacement. It is shown how to organize the calculation of displacement and centre of gravity in an electronic spreadsheet or in MATLAB. The chapter continues by showing how to calculate the trim. Because of uncertainties in the calculation of masses and centres of gravity, it is necessary to validate them by an inclining experiment. Bonjean curves are often used for the analysis of inclining-experiment results.
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