PART TWO 



SNAME HS-2-1 Program 



The S-6 Panel (Hydrostructure Vibration) was organized in August 1953 under the di- 

 rection of the Hull Structure Committee of The Society of Naval Architects and Marine Engi- 

 neers. Probably the best definition of the purpose and objectives of the S-6 Panel was pre- 

 sented in October 1960 and were as follows: 



1. To investigate the response of ship structures to exciting forces and thereby develop 

 recommendations which would lead to assured satisfactory ship vibration characteristics. 



2. To recommend and support research directed toward an improved understanding of the 

 response of ship structures to exciting forces. 



3. To recommend publication of vibration design criteria and guides, through SNAME. 



The program objectives of the S-6 Panel are presently being carried out under the 

 newly formed Panel HS-2 (Dynamic Loadings and Responses). This Panel held its first 

 meeting on 15 February 1962 at which the total interest of the Panel was assigned to three 

 distinct Task Groups: 



1. Vibration Task Group HS-2-1 



2. Surge Loadings Task Group HS-2-2 



3. Slamming Task Group HS-2-3 



I. THE "NORM" PROGRAM 



A. BACKGROUND 



The vibration of ship hulls and various local structures is the result of I — Forced vi- 

 bration induced by the propulsion machinery, shafts or propellers, or II — Random vibration 

 induced by hydrodynamic forces acting on the hull during rough weather operation. Both 

 types of vibration are of importance in the design and construction of commercial as well as 

 naval ships. 



The first type, forced (or steady-state) vibration, is generally associated with propel- 

 ler blade or shaft frequencies or with the major forces in the main machinery. This forced 

 vibration may be resonant or nonresonant and is of particular importance in determining the 

 acceptability of the hull vibration levels under normal trial or operating conditions (sea con- 

 ditions not greater than 3 as defined by the U. S. Navy Hydrographic Office Sea State Code.) 



The second type, random (or transient) vibration, is generally associated with the nat- 

 ural frequencies of the hull or structural subassemblies excited by wave impact or pounding 

 of the ship in heavy seas. This vibration is random in nature, is a function of sea conditions, 



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