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Preliminary communication

An Approach to Calculation of Marine Machinery Flexible Seating

Nenad Vulić ; Hrvatski registar brodova, Split
Ante Šestan ; Fakultet strojarstva i brodogradnje Sveučilišta u Zagrebu
Jani Barle ; Fakultet elektrotehnike, strojarstva i brodogradnje Sveučilišta u Splitu

Fulltext: croatian, pdf (1 MB) pages 127-136 downloads: 1.008* cite
APA 6th Edition
Vulić, N., Šestan, A. & Barle, J. (2008). JEDAN PRISTUP PRORAČUNU ELASTIČNOG TEMELJENJA BRODSKIH STROJEVA. NAŠE MORE, 55 (3-4), 127-136. Retrieved from
MLA 8th Edition
Vulić, Nenad, et al. "JEDAN PRISTUP PRORAČUNU ELASTIČNOG TEMELJENJA BRODSKIH STROJEVA." NAŠE MORE, vol. 55, no. 3-4, 2008, pp. 127-136. Accessed 23 Jul. 2019.
Chicago 17th Edition
Vulić, Nenad, Ante Šestan and Jani Barle. "JEDAN PRISTUP PRORAČUNU ELASTIČNOG TEMELJENJA BRODSKIH STROJEVA." NAŠE MORE 55, no. 3-4 (2008): 127-136.
Vulić, N., Šestan, A., and Barle, J. (2008). 'JEDAN PRISTUP PRORAČUNU ELASTIČNOG TEMELJENJA BRODSKIH STROJEVA', NAŠE MORE, 55(3-4), pp. 127-136. Available at: (Accessed 23 July 2019)
Vulić N, Šestan A, Barle J. JEDAN PRISTUP PRORAČUNU ELASTIČNOG TEMELJENJA BRODSKIH STROJEVA. NAŠE MORE [Internet]. 2008 [cited 2019 July 23];55(3-4):127-136. Available from:
N. Vulić, A. Šestan and J. Barle, "JEDAN PRISTUP PRORAČUNU ELASTIČNOG TEMELJENJA BRODSKIH STROJEVA", NAŠE MORE, vol.55, no. 3-4, pp. 127-136, 2008. [Online]. Available: [Accessed: 23 July 2019]

Marine propulsion and auxiliary machinery are seated on stiff seating (metal supports or resin chocks) or flexible seating (elastic supports with rubber parts). The basic purpose of flexible seating is to reduce detrimental influence of vibrations and direct transfer of noise to the ship structure. Consequentially, flexible seating is usually implemented in passenger ships.

The aim of this paper is to present a simplified procedure for calculation of flexible seating for marine machinery, in order to ease the work of designers of marine propulsion and auxiliary machinery. The simplified calculation basically contains of evaluation of static forces in the flexible supports, as well as the natural frequencies for the six degree-of-freedom system, from which critical rotational speeds can be determined. The calculation is presented in matrix form (similar to the conventional FEM calculations of linear elastic systems) with all the necessary details enabling a designer’s autonomous work. Generally, the methodology of calculation of system dynamic response to forced damped vibrations is also presented.

The contribution of the paper is in the calculation methodology presented in matrix form, as well as in the proposal to avoid evaluation of excitation forces. Under certain conditions it is enough to know only the frequency of the excitations, caused by internal combustion engine cylinders and propeller in operation, but not their magnitude or phase, as well as to compare that frequency in Campbell diagram with the calculated natural frequencies to make the decision about the necessity of more complex approach.

An example of calculation results for the flexibly mounted propulsion system of a series of newbuildings, built in a domestic shipyard, has been presented, together with the comparison with the measurement results from the literature on the first ship. It is concluded that the calculation of flexible seating should not be avoided in practice, what is a common situation. Contrary, by implementing the proposed simplified calculation procedure the necessary static and dynamic analyses should be performed. This is the way to avoid difficulties during the design phase early enough, which are not easy to deal with later on.

marine machinery; flexible seating; critical speeds; Campbell diagram

Hrčak ID: 29434



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