EVALUATION OF HULL VIBRATORY (SPRINGING) RESPONSE OF GREAT LAKES ORE CARRIER M/V STEWART J. CORT

The hull vibration (springing) of the Great Lakes ore carrier STEWART J. CORT was evaluated on the basis of accelerometer and strain gage data collected during a regular round trip voyage between Burns Harbor, Indiana, and Taconite Harbor, Minnesota, in August 1972. Springing was recorded when in the loaded condition, CORT encountered 4- to 6-ft seas, 60 deg to the bow in Lake Superior. The maximum first mode deflection profile and midship bending stress were determined from a direct analysis of this springing record. A spectrum analysis of the same record produced flexural frequencies of vibration for the first three vertical modes and what appeared to be the first horizontal mode, rms deflection profiles for the first three vertical modes, and the first mode rms midship bending stress. An important finding of the investigation was that the springing deflections of the CORT involved larger contributions than expected from the second flexural mode of vibration. Although the contribution of the second mode to midpoint bending stress is theoretically zero, its contribution to bending stresses at other points merits consideration. An evaluation of first vibratory mode damping by means of ten anchor drop tests was unsuccessful, partly because CORT underwent springing while at zero speed in a 1-ft sea. The springing appeared to interfere with the anchor-drop-induced ship response.

• Corporate Authors:

  Naval Ship Research and Development Center

  Structures Department
  Bethesda, MD  United States  20034
• Authors:
  • Critchfield, M O
• Publication Date: 1973-11

Media Info

• Features: References;
• Pagination: 45 p.

Subject/Index Terms

• TRT Terms: Bending stress; Flexural strength; Hulls; Longitudinal strength; Measurement; Ships; Vibration
• Old TRIS Terms: Hull springing; Hull vibration; Vibration measurement
• Subject Areas: Marine Transportation; Materials; Vehicles and Equipment;

Filing Info

• Accession Number: 00051237
• Record Type: Publication
• Source Agency: Naval Ship Research and Development Center
• Report/Paper Numbers: NSRDC-4225
• Files: TRIS
• Created Date: Feb 28 1974 12:00AM