Damien Holloway | University of Tasmania (original) (raw)

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Papers by Damien Holloway

Construction and Building Materials, 2022

The earliest catamaran ferries were essentially conceived for use in very sheltered waters such a... more The earliest catamaran ferries were essentially conceived for use in very sheltered waters such as river, estuary and bay crossings and for routes protected by offshore reefs where tour crossings were easily postponed in rough weather. They were therefore designed with relatively small wet deck heights (height of the underside of the central deck above the water line) and thus with a relatively low transverse deck structure at the bow. However, the speed capability and length of these vessels gave rise to length based Froude numbers of 1.0 (Figures 2 and 3) and it became apparent that wave encounter induced significant vessel motions. Therefore if such vessels were operated in significant seas there resulted not only increased passenger discomfort but also increased risk of wave slam impact on the bow and wet deck. To overcome these problems the wave piercing and semi-SWATH (small water plane area twin hull) designs were introduced (Figures 4 and 5) so as to reduce the vessel motion...

Many recent studies have sought to assess the acoustical experience of musicians playing in ensem... more Many recent studies have sought to assess the acoustical experience of musicians playing in ensembles through development of acoustic measures undertaken on stage in auditoria. It is generally proposed that such measures be undertaken in the presence of stage furniture to better replicate the real conditions onstage with an ensemble present. However, conditions are arguably not necessarily realistic because furniture is customarily removed within 2m radii of the source and receiver to avoid disturbing reflections, and because it is seldom practical to make the measurements with the musicians present. Furthermore, consistency of conditions is also potentially an issue. This paper uses BEM (boundary element method), validated against published full and model scale data, to investigate the differences between sound fields on a stage with an orchestra present and on a bare stage. Sensitivity to perturbations of the stage configuration is also investigated. The results of this study show...

International Journal of Maritime Engineering, 2012

To assess the behaviour of large high-speed catamarans in severe seas, extensive full-scale trial... more To assess the behaviour of large high-speed catamarans in severe seas, extensive full-scale trials were conducted by the U.S. Navy on an INCAT Tasmania built vessel in the North Sea and North Atlantic region. Systematic testing was done for different speeds, sea states and ride control settings at different headings. Collected data has been used to characterise the ship’s motions and seakeeping performance with respect to wave environment, vessel speed and ride control system. Motion response amplitude operators were derived and compared with results from a two-dimensional Green function time-domain strip theory seakeeping prediction method. An increase of motion response with increasing vessel speed and a decrease with the vessel moving from head to beam seas was found. In higher sea states and headings ahead of beam seas an increasing influence of the centre bow on pitch motion damping was found. Significant motion RAO reduction was also found when the ride control system was acti...

ANZIAM Journal, 2014

Frequency content of a periodic signal is easily computed using fast Fourier transforms (fft). Wh... more Frequency content of a periodic signal is easily computed using fast Fourier transforms (fft). While the magnitude is well predicted, phase information is usually meaningless and temporal changes are difficult to resolve accurately over short time periods, even with techniques such as discrete time Fourier transforms or wavelets. These problems arise in the analysis of musical sounds and should be solvable since a well trained human ear can detect subtle and rapid changes to timbre and pitch that occur with expressiveness, techniques such as 'vibrato', and lack of tone control exhibited by music students. Starting with the premise that a musical sound is truly periodic, we obtain much more accurate information from a Fourier series than from a Fourier transform. In this article the Fourier series of a periodic signal is evaluated using a least

Australian Journal of Structural Engineering, 2019

This paper investigated the behaviour of locally post-tensioned nail laminated high mass floor pa... more This paper investigated the behaviour of locally post-tensioned nail laminated high mass floor panels. Each panel was assembled using butt jointed timber boards. Post tensioning was applied using bracing straps. A total of six panels were tested under four-point bending. The dynamic behaviour of the floor panels was also investigated Results showed that posttensioning reduced the deflection by almost 50% under the serviceability loading condition. However, the damping ratio was reduced under dynamic tests, though it remained within acceptable limits.

Australian Journal of Mechanical Engineering, 2007

This paper investigates the effects of stiffness and mass distribution on the longitudinal fl exu... more This paper investigates the effects of stiffness and mass distribution on the longitudinal fl exural natural frequency response of an NPL 6A segmented monohull model in still water at zero speed. Experimental tests were undertaken in order to establish the parameters that affect the whipping frequency at model-scale so as to replicate the vibratory response of a full-scale vessel subject to slamming. The model was cut into two halves at the longitudinal centre of buoyancy and connected by a backbone beam with an elastic hinge joining the two segments. Wet vibration tests conducted on the model showed signifi cant infl uences on the fl exural natural frequency response through variations in stiffness and ballast mass distribution. The whipping frequency was predicted with a two degree of freedom theoretical model using an added mass approximation to provide good correlation with measured experimental data. Damping ratios of the wet transient response are also presented with respect to variations in the condition of the void separating the two model halves.

Proc. 8 th Int. Conf. on Fast Sea …, 2005

Buildings

In this study, the preliminary serviceability performance of cross-laminated timber (CLT) panels ... more In this study, the preliminary serviceability performance of cross-laminated timber (CLT) panels constructed from fibre-managed Eucalyptus nitens (E. nitens) was investigated via bending and vibration tests. Linear four-point bending tests were performed to determine the stiffness and deflection of all CLT panels under serviceability loads. The dynamic response of CLT panels was tested using a basketball and an accelerometer. The fundamental natural frequencies of all tested panels were above the minimum frequency limit (8 Hz) when extrapolated to spans of up to 4.4 m. The configurations of E. nitens CLT panels were based on different modulus of elasticity (MOE) values for each board. Using higher MOE timber boards as the top and bottom layers can significantly increase the serviceability performance of both bending and vibration tests. The same experiments were carried out on two CLT panels made of strength class C24 Spruce-Pine-Fir to compare the serviceability performance of E. n...

International Journal of Maritime Engineering

The estimation of fatigue life in the design process is particularly important for weight-optimis... more The estimation of fatigue life in the design process is particularly important for weight-optimised ships such as high-speed aluminium craft, but to date no research has been published on the fatigue accumulation on large wave-piercing catamarans, focusing on long-term operations. This paper assesses the applicability of classification society rules for high-speed catamarans with respect to fatigue design. This was achieved by comparing the long-term distributions of stress, measured on a 111m long wave-piercing catamaran ferry whilst operating in the Canary Islands and during the delivery voyage, with load spectra estimated using a method accepted by the classification society, DNV. The paper also proposes an improved distribution fitment method for fatigue analysis. A detailed method to convert measured stress histories in the time domain into an appropriate stress-spectrum and fitment of Weibull parameters is presented. Results show that the simplified method accepted by the clas...

International Journal of Maritime Engineering, 2021

Ride control systems on high-seed vessels are an important design features for improving passenge... more Ride control systems on high-seed vessels are an important design features for improving passenger comfort and reducing motion sickness and dynamic structural loads. To investigate the performance of ride control systems a 2.5m catamaran model based on the 112m INCAT catamaran was tested with an active centre bow mounted T-Foil and two active stern mounted trim tabs. The model was set-up for towing tank tests in calm water to measure the motions response to ride control step inputs. Heave and pitch response were measured when the model was excited by deflections of the T-Foil and the stern tab separately. Appropriate combinations of the control surface deflections were then determined to produce pure heave and pure pitch response. This forms the basis for setting the gains of the ride control system to implement different control algorithms in terms of the heave and pitch motions in encountered waves. A two degree of freedom rigid body analysis was undertaken to theoretically evalua...

Wavelet analysis identifies slamming events during sea trials. Maximum loads, load impulses and e... more Wavelet analysis identifies slamming events during sea trials. Maximum loads, load impulses and energy imparted to the structure by slams have been evaluated. A segmented hydro-elastic model has been developed to simulate the main whipping mode, elastic links in the model facilitating measurement of bending moments and determination of slam loads. Slams of up to 2200 tonnes peak force can occur when the wet deck arches between the main hulls and centre bow fill, imparting impulses of up to 938 tonne seconds and 3.5 MJ of strain energy. Energy is transferred to the whipping mode which has a damping ratio in the range 0.02 to 0.06 depending upon forward speed.

$Research paper thumbnail of Boundary element modelling of fractal and other enhanced bandwidth Schroeder diffusers$

It is well established that Schroeder diffusers may be used as surface treatment to promote diffu... more It is well established that Schroeder diffusers may be used as surface treatment to promote diffuse sound fields in auditoria over a target frequency range. Quadratic Residue Diffusers are very effective within a design frequency bandwidth, and this frequency bandwidth may be significantly extended by a nested or fractal design. Publicly available data typically publishes diffusion coefficients separately for the parent diffuser and the child diffuser, with some ambiguity surrounding the effect the two levels have on each other, and the performance at 'crossover' frequencies. This paper uses an optimised 2D boundary element method to investigate the differences in results when the parent and child diffusers are modelled separately, and as an integrated design. It is found that the scattering properties of the child diffuser are significantly modified by the well of the parent diffuser in which it is placed. More interestingly, the excellent scattering properties of the fract...