Test results for lead-rubber bearings for Wm. Clayton Building, Toe Toe Bridge and Waiotukupuna Bridge

Four lead-rubber bearings designed to base isolate structures from earthquake attack were tested for the Ministry of Works and Development on PEL’s dynamic test rig. The lead-rubber bearings ranging in size up to 600 mm square, consisted of elastomeric bearings containing lead plugs. In the case of the Wm Clayton Building two bearings were selected at random from 82, of which
 80 have been installed under the building, and were tested at 
0.3 Hz with strokes of + 20, + 45 and + 110 mm, and vertical loads of 1.05, 2.10 and 3.15 MN. For the two bridges one bearing from each was tested at 0.9 Hz with vertical loads of 160 to 350 kN, and strokes of + 30 to 93 mm. In all cases the bearings performed satisfactorily over 9 to 35 cycles and the hysteresis loops could be described reasonably well by assuming that the lead behaved as a plastic solid with a yield stress of 10 MPa.