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A state-of-the-art review on seismic design of bridges - Part II : CALTRANS, TNZ and Indian codes
Published in
1998
Volume: 72
   
Issue: 3
Pages: 129 - 138
Abstract
In a companion paper1, the historical development of the seismic design provisions for bridges in USA are studied and it is shown how the experience of the performance of bridges during past earthquakes has been translated into the AASHTO code. In this paper, code provisions on seismic design of bridges in California, USA (CALTRANS code) and New Zealand (TNZ code) are reviewed in detail, together with those in the Indian codes (IS : 1893-1984 and IRC : 6-1966). In the American and New Zealand codes, more realistic ground accelerations are explicitly considered in design, suitable response reduction factors are used to account for ductility and overstrength, and the principle of capacity design is liberally used. This results in a bridge structure which is likely to display ductile behaviour in the event of very strong shaking. Moreover, these codes provide specifications for vertical hold-down devices and horizontal linkage elements; these devices provide positive anchorage and stability against lateral and longitudinal displacements and against vertical uplift. Finally, to prevent loss-of-span type of collapses, these codes require minimum seating widths. It is seen that, generally, the seismic design force for bridges in the current Indian codes is extremely low, particularly for the connections (such is not the case for the buildings). The Indian codes require major changes regarding (i) more realistic earthquake ground accelerations (ii) consideration of flexibility of structure in design force calculation, and (iii) provision of proper response reduction factors for different elements of the bridges to account for ductility and overstrength. Also, there is an urgent need to incorporate provisions on vertical hold-down devices and horizontal linkage elements, and minimum seat widths.
About the journal
JournalIndian Concrete Journal
ISSN00194565
Open AccessNo