BURLINGAME, CALIF. - The U.S. Navy will apply two or three layers of carbon fiber-reinforced plastic to concrete pier slabs at its Norfolk, Va., station this year in an effort to upgrade and strengthen their load-carrying capacity. Now, enormous pressures on extended outrigger support legs for large truck-mounted mobile loading cranes can punch holes through the reinforced concrete slabs, Christopher Inaba, a Navy research structural engineer, said at the Wilson Forum, held March 11-12 in Burlingame.
The piers were designed to accommodate rail-mounted cranes and have heavy supporting beams and girders.
The deck areas surrounding these beams and girders, however, cannot support the outrigger pad loads, which can exceed 110 tons on a 30-inch-square area. The cranes have capacities to 170 tons.
Inaba said composites may be applied on pier slabs at Naval stations at Pearl Har-bor in Hawaii and 32nd Street in San Diego.
Tests at the Naval Facilities Engineering Service Center at Port Hueneme, Calif., found that the fiber upgrade im-proved slab shear strength 31-47 percent. For the testing, the Navy bonded one or two layers of Tonen Corp.'s unidirectional carbon Forca tow sheet C1-20 to the bottom of under-reinforced slabs.
``The CFRP sheets were able to enhance the punching shear resistance by providing increased in-plane re-straint,'' Inaba said.
CFRP is seen as an alternative to replacement of aging waterfront facilities in an era of budget constraints and changing mission requirements.