The importance of the vibration encountered is of course dependent upon the forces 

 generated, the response of the hull girder and the magnification of the hull girder motion in 

 the local structures of the ship, such as panels, masts, bulkheads, etc. It is reasonable to 

 say that a good design is one in which both the exciting forces and the magnification of 

 these forces in the hull are kept to a minimum. What the reasonable minimum would be for 

 any particular type or class of ship necessarily is dependent on many factors. 



By empirical methods, by the collection of existing data, and by obtaining test data 

 during the builder's trials of new ships, it is proposed to: 



(1) Develop "Norms" for various classes of ships; and 



(2) Classify the important design factors which contribute to the general level of vibra- 

 tion existing on any particular class of ship. 



On the theory that the acceptable vibration may be based on the considerations of what 

 minimum levels have been obtained on a given type or class of ship as well as on the physio- 

 logical response of passengers and crews, it is considered reasonable and practical that this 

 program will produce a set of suitable recommendations for the guidance of ship designers and 

 shipbuilders, in developing ships having more satisfactory vibration characteristics. 



D. PROGRAM 



The "Norm" Program was planned in three phases: 



Phase 1 — Conduct vibration tests on several ships to establish a "Vibration Trial 

 Code" and specifications for a "Standard Instrumentation Package." 



Phase 2 — Obtain acceptance of the Trial Code by the Society; find sponsorship for 

 the purchase of the instrumentation package; and establish a method for conducting standard 

 vibration tests on a large number of ships. 



Phase 3 — Conduct statistical treatment of vibration data collected in accordance with 

 the procedure developed under Phase 2; establish vibration reference levels or "norms" for 

 various classes of ships tested in accordance with the requirements of the Vibration Code; 

 and attempt correlation of vibration levels with design data. 



As of this writing Phase 1 has been completed. The "Vibration Code" has received 

 the approval of the Hull Structure Committee and appears as Section III of this report on the 

 SNAME HS-2-1 Program. The Maritime Administration has indicated a willingness to support 

 the purchase of the "Standard Instrumentation Package" and purposes to call for the neces- 

 sary vibration tests to be included as a part of the builder's trials for all ships built under 

 the sponsorship of the Maritime Administration. 



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