Abstract
In the Weber earthquake of 13 May 1990 the stronger component of the ground motions recorded in Dannevirke was similar in strength to the El Centro S00E record from the 1940 Imperial Valley earthquake which underlies the New Zealand loadings code, The Modified Mercalli intensity in Dannevirke however was only about MM7 1⁄2, whereas the intensity corresponding to the 1984 earthquake code is about MM8 1⁄2 for the Dannevirke area. This paper compares the strength of the Dannevirke record in terms of spectral accelerations with (i) the above El Centro record, (ii) the Matahina dam record of the 1987 Edgecumbe earthquake, and (iii) the loadings of the 1984 and 1992 New Zealand codes. Also described in the paper are time-history analyses of one- and two- storey buildings subjected to the above ground motions in an attempt to explain why the damage levels were lower than might be expected from the strength of the recorded accelerograms. Comparisons are made of the seismic performance of moment-resisting frames and walled structures. Comments are made on two of the provisions of the 1992 loadings code.
Highlights
Trifunac and Brune reported that in the 1940 event there were two sub-events with ML values in the range of 5.9-6.2 with epicentres approximately 7-23 km from the recording site in this short time interval. These magnitude and distance ranges of the 1940 Imperial Valley earthquake together with the soil conditions at El Centro are similar to those of the Dannevirke record
From the DRAIN-2DX analyses it is predicted that the bare frame moment-resisting frame (MRF) structure, designed to the 1984 code, would have suffered considerable damage to its columns, if subjected to any of the three moderate ground motions considered here. (This assumes that the building is truly "bare frame" in behaviour, with negligible stiffness contribution from cladding or partitions.) It may be inferred that a similar building designed to the loadings of the 1992 code, but without capacity design, would perform better because the design strength required by the 1992 code is over 35 percent higher than that required by the 1984 code for Models 1 and 2
1.1 Both of the Dannevirke buildings studied, the *precode era unreinforced brick masonry building (UBM) building and the two-storey reinforced masonry (RM) Post Office, had very short fundamental periods (T :,; 0.077 s). The responses of both buildings were those of nearly rigid structures, and the high spectral accelerations obtained for the Dannevirke spectrum at slightly greater periods (T 2". 0.13 s) were irrelevant to their responses
Summary
In the Weber earthquake of 13 May 1990 the stronger component of the ground motions recorded in Dannevirke was similar in strength to the El Centro S00E record from the 1940 Imperial Valley earthquake which underlies the New Zealand loadings code, The Modified Mercalli intensity in Dannevirke was only about MM71⁄2, whereas the intensity corresponding to the 1984 earthquake code is about MM81⁄2 for the Dannevirke area. This paper compares the strength of the Dannevirke record in terms of spectral accelerations with (i) the above El Centro record, (ii) the Matahina dam record of the 1987 Edgecumbe earthquake, and (iii) the loadings of the 1984 and 1992 New Zealand codes. Described in the paper are time-history analyses of one- and twostorey buildings subjected to the above ground motions in an attempt to explain why the damage levels were lower than might be expected from the strength of the recorded accelerograms. Comments are made on two of the provi,sions of the 1992 loadings code
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