The impact of wave slamming indused vibration on human factors and equipment on board the SA Agulhas II

Omer, Hamza (2016-03)

Thesis (MEng)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: An investigation of wave slamming phenomenon was performed in the context of human factors on-board the S.A. Agulhas II, a South African Polar Supply and Research Vessel. Full scale vibration measurements were conducted during the vessel’s voyage to Marion Island in 2014 and Antarctica in 2014/15. The measurements captured vibrations in the vertical direction as per the directives of ISO 2631-1 (1997). A questionnaire survey was conducted on both voyages to acquire the human response to wave slamming. The study for the Marion Island voyage focused on measurement and analysis of vibration due to slamming using the metrics recommended by ISO 2631-1 (1997). The analysis revealed that slamming events produce impulsive accelerations of high magnitude resulting in broad band excitation of the vessel. The weighted r.m.s acceleration levels resulting from slamming exceeded the comfort threshold provided by the standard. The qualitative analysis of human response indicated that slamming not only caused discomfort on-board but also affected work and equipment. The study performed during the Antarctic voyage was designed to identify and correlate measured slamming vibration data with human response and to investigate their association. Statistical analysis, performed using Kendall’s coefficient, indicated that slamming vibration was correlated to human complaints on-board the S.A. Agulhas II. The highest correlation found was the cumulative Vibration Dose Values (VDV) which proved to be the best metric amongst all others to represent slamming vibration for human factors. In addition to that, the study evaluated the effects of some environmental factors such as swell height and wind speed on wave slamming. It was concluded that even moderate sea states can lead to heavy incidences of slamming. Finally, operational deflection shapes were calculated for the visualization of the structural response of the vessel during bow and a stern slamming event. Time domain response and frequency response was calculated to observe the motion of the ship as it undergoes a slamming event. The analysis indicated that the area of impact (bow or stern) comes under severe loading immediately. Both slamming events produce bending and twisting of the entire structure. It was also noted that the long duration of heavy oscillations produced by slamming may affect human comfort and performance on-board the vessel.

AFRIKAANSE OPSOMMING: Ondersoek is ingestel oor die menslike impak van ‘n branderklap-verskynsel aan boord die S.A. Agulhas II, ’n Suid-Afrikaanse Voorraad-en-navorsingskip. Volskaal vibrasie-metings is op die skip uitgevoer tydens vaarte na Marioneiland in 2014 en Antarktika in 2014/15. Die metings het vibrasies opgeneem in die vertikale rigting soos per die aanwysings van ISO 2631-1 (1997). ’n Opname was ook uitgevoer op beide vaarte om die menslike reaksie tot branderklap te verkry. Die studie vir die Marioneiland-vaart het gefokus op die meting en analise van vibrasie as gevolg van branderklap deur gebruik te maak van die maatstawwe soos aanbeveel deur ISO 2631-1 (1997). Die analise het getoon dat branderklap impulsiewe versnellings van beduidende grootte produseer wat lei to breë-band opwekking van die skip. Die geweegde w.g.k. vlakke versnellings veroorsaak deur branderklap het die standaard se ongemak drumpelwaarde oorskry. Die kwalitatiewe analise van menslike reaksie het aangedui dat branderklap nie net ongemak aan boord veroorsaak het nie, maar ook werk en toerusting geaffekteer het. Die studie uitgevoer tydens die Antarktiese vaart is ontwerp om die gemete branderklap vibrasiedata te identifiseer en te korreleer met menslike reaksie en die verband daartussen te ondersoek. Statistiese analise, uitgevoer met behulp van Kendall se koeffisiënt, het aangedui dat branderklap vibrasie gekorreleer is met menslike klagtes aan boord die S.A. Agulhas II. Die hoogste korrelasie wat gevind is, was die kumulatiewe Vibrasie Dosis Waarde (VDW) wat die beste maatstaf van almal was om die branderklap vibrasies vir menslike faktore te verteenwoordig. Daarby het die studie die effek van omgewingsfaktore soos deining-hoogte en windspoed op branderklap evalueer. Die gevolgtrekking dat selfs matige seetoestande kan lei to beduidende insidensies van branderklap is gemaak. Operasionele defleksie vorms is uitgewerk vir die visualisering van die strukturele reaksie van die skip tydens ’n boeg en agterboeg branderklap gebeurtenis. Tyddomein respons en frekwensie respons is apart uitgewerk om die beweging van die skip waar te neem wanneer dit ’n branderklap beurtenis ondergaan het. Die analise het aangedui dat die area van impak (boeg of agterboeg) onmiddelik onder belasting verkeer. Beide branderklapgebeure lei tot buiging en verwringing van die golbale struktuur. Daar word ook waargeneem dat die lang duur van ossilasies geproduseer deur branderklap menslike gemak en uitvoering prestasie op die skip kan affekteer.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98628
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