ALBERT

Description: The region in and around Christchurch, encompassing Christchurch city and the Selwyn and Waimakariri districts, contains more than 800 road, rail, and pedestrian bridges. Most of these bridges are reinforced concrete, symmetric, and have small to moderate spans (15–25 m). The 22 February 2011 moment magnitude (Mw) 6.2 Christchurch earthquake induced high levels of localized ground shaking (Bradley and Cubrinovski 2011, page 853 of this issue; Guidotti et al. 2011, page 767 of this issue; Smyrou et al. 2011, page 882 of this issue), with damage to bridges mainly confined to the central and eastern parts of Christchurch. Liquefaction was evident over much of this part of the city, with lateral spreading affecting bridges spanning both the Avon and Heathcote rivers. The majority of bridge damage was a result of liquefaction-induced lateral spreading, with only four bridges suffering significant damage on non-liquefiable sites. Abutments, approaches, and piers suffered varying levels of damage, with very little damage observed in the bridge superstructure. However, bridges suffered only a moderate amount of damage compared to other structural systems. Because some bridges critical to the city infrastructure network sustained substantial damage, extensive traffic disruption occurred immediately following the event. This paper presents a summary of field observations and subsequent analyses on the damage to some of the bridges in the Canterbury region as a result of the Christchurch earthquake. Reference is also made to the performance of bridges following the 4 September 2010 Mw 7.1 Darfield earthquake (Gledhill et al. 2011), and details of damage progression are presented where applicable. The ground motion characteristics for both events and the regional soil conditions are first described. We provide descriptions of the damage at each selected bridge site and compare observations of liquefaction with predicted response using in situ test data...