Page 21: of Maritime Reporter Magazine (October 1973)

Study Of Hull Stresses

Published By SNAME

Three companion publications presenting the results of a Tour- year study of the wave climate of the Great Lakes and the Associated hull stresses in the bulk ore car- riers which ply them are now avail- able. The data included in these publications should prove extreme- ly valuable to organizations design- ing building or operating ships for the Great Lakes or the Gulf of St.

Lawrence, as well as offshore drill- ing contractors and rig owners, construction-equipment contractors and others serving the offshore pe- troleum industry.

In 1965, The Society of Naval

Architects and Marine Engineers in cooperation with Government, regulatory, and industry organiza- tions in the United States and

Canada implemented an extensive program 'to analyze the Great

Lakes and Gulf of St. Lawrence wave climate and the forces in- duced by these waves acting upon large bulk carriers up to 1,000 feet in length. Wave and sea-state rec- ords were obtained using moored and shipdaunched remote indicat- ing buoys, wave staffs and gauges, ship observations and weather sta- tions. At the same time, four Great

Lakes bulk ore carriers were in- strumented to measure the hull stresses which are simultaneously induced by these waves. This four- year program was reported in T&R

Bulletins 2-17, "Wave Climate

Study, Great Lakes and Gulf of St.

Lawrence," and 2-18, "Seaway

Stresses Observed Aboard Great

Lakes Bulk Ore (Carrier Edward

L. Ryerson (1965-1968)." In addi- tion, to evaluate the progress achieved in 'the first four years of tihe program, the 'Society spon- sored a symposium in the summer of 1971 at which 13 technical pa- pers were presented, discussed, and published in Symposium Report

S-2, "Hull Stresses in Bul'k Carriers in the Great Lakes and Gulf of

St. Lawrence Wave Environment."

The wave climate study, coor- dinated by Task Group HiS-1-1 (Great Lakes Waves) of the So- ciety's Technical and Research

Program, was exceptionally thor- ough and complete with some 18,000 usable wave records collect- ed from recording stations at 14 various locations in the Great

Lakes and the Gulf of St. Lawrence during 1965, 1966, and 1967. Each record represented a 20-minute ob- servation 'period and is presented in tabular form in Bulletin 2-17 showing the date and 'time of each record, the significant wave heights (from direct spectral analysis), fre- quencies at which the peaks of the displacement spectra occurred, pe- riods corresponding to peak fre- quencies, and other parameters representing wave steepness and slope. An explanation of the analy- sis procedure is also included.

While the wave study was in progress, Task Group H'S-1-2. (Wave Loads-Great Lakes Ves- sels), sought to relate wave-in- duced stresses in a typical modern

October 1, 1973 ore carrier operation on the Great

Lakes with measured wave and weather data. They accomplished this objective by instrumenting the 730-foot STR. Edward L. Ryerson, at 'that time one of the largest vessels navigation regulations would permit on the Lakes. The program of stress measurement uncovered the unique phenomenon referred to as "springing stresses" believed to be a result of hull excita- tion at the fundamental (two noded) 'frequency of the hull. T&R

Bulletin 2-18 describes in soijie de- tail the characteristics of the ves- sel, the instrumentation system, the tests made to verify the quality of the data, and a review of the stress and wave data acquired and analyzed over the four operating seasons, 1965-1968.

Increasing the allowable length of these vessels to 1,000 feet, due to the enlarging of the locks at

Sault Ste. Marie and the continued interest in the newly uncovered phenomenon of springing, encour- aged further research into hull stress characteristics. Model stud- ies of Ihul'l bending moments were performed at Davidson Laboratory and plans outlined for the instru- mentation of the 1,000-foot bulk ore carrier, M/V 'Stewart J. Cort.

The results of this ongoing re- search and the various interpreta- tions of the wave climate and Ryer- son studies were presented at the symposium held in Ottawa, Can- ada, during the summer of 1971.

The complete program of 13 tech- nical papers along with the dis- cussion and comments they gener- ated at the time of presentation are all included in T&R Symposium

Report S-2 "Hull Stresses in Bulk

Carriers in the Great Lakes and

Gulf of St. Lawrence Wave Envi- ronment." The topics discussed in- clude, among others, historical background of Great Lakes vessels, wave climate analysis and obser- vations, bulk carrier model bending moment experiments, analysis of springing stresses, the Great Lakes

Load Lines strength standards and freeboard requirements for Great

Lakes bulk ore carriers.

Significantly, the results of this research endeavor as outlined in the 475-page Symposium Report helped to justify a substantial re- duction in the Great Lakes winter seasonal freeboard permitting some large 'bulk ore carriers to carry approximately another extra thou- sand tons of cargo during the win- ter season. This certainly repre- sents a substantial direct viable return on an investment in applied research.

The research work reported above is continuing with the in- strumentation of both tlhe 1,000- foot M/V Stewart J. Cort and the 806-foot 'STR. Charles M. Beeghly, along with a ship model test pro- gram to measure the springing bending moment response of a 1,000-foot ore ship. Supplemental publications will be available fol- lowing the analysis of the addition- al data being obtained.

These three Society publications represent a compendium of Great

Lakes bulk ore carrier hull and wave climate research and are available through The Society of

Naval Architects and Marine En- gineers, 74 Trinity Place, New

York, N.Y. 10006, as follows: 2-17 "Wave Climate Study, Great

Lakes and Gulf of St. Lawrence," at a price of $9 each. Members may obtain a copy for $6. 2-18 "Seaway Stresses Observed

Aboard Great Lakes Bulk Ore Car- rier Edward L. Ryerson (1965- 1968)," at a price of $9 each. Mem- bers may obtain a copy for $6.

S-2 "Hull Stresses in Bulk Car- riers in the 'Great Lakes and Gulf of St. Lawrence Wave Environ- ment," at a price of $30 each. Mem- bers may obtain a copy for $20.

All prices include postage, if payment is received with order, via third class mail in the United

States and as "Printed Matter" in all other countries. Shipments will be insured or sent air mail at addi- tional cost if requested.

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