Local ice pressures measured on a strain gauge panel during the CCGS Terry Fox bergy bit impact study

A field test program was carried out with the CCGS Terry Fox off the northeast coast of Newfoundland in June 2001. During these trials, a total of 178 impacts occurred between the vessel and bergy bits whose sizes ranged from 20 t to 22,000 t, at ship speeds from 0.2 to 6.5 m/s.An area on the port bow was instrumented using 120 strain gauges. An in situ calibration of the instrumented area was performed to measure the response of the various gauges to a known load. A finite element model of the instrumented area was developed. The in situ measurements were used to validate and adjust the finite model. Using the calibrated finite element model, strains measured on the hull structure were converted into pressures on the hull.Of the 178 ship–bergy bit impacts, 60% caused loads on the area of the hull instrumented with strain gauges. The maximum pressure measured was 11.3 MPa on an area of 0.12 m2 and maximum force of 5 MN was measured on the instrumented area during a direct impact. From the pressures measured, pressure–area curves were developed, total forces were calculated and the correlation between various parameters such as velocity and bergy bit mass was analyzed.