ABSTRACT
For elevated highway bridges in urban areas shown in Figure 10.1, thin-walled hollow steel piers and concrete-lled tubular (CFT) piers are oen preferred to reinforced concrete (RC piers) piers in Japan, because those piers make it possible to reduce cross-sectional size as well as construction period. Before the 1995 Kobe earthquake (Hyogo-ken Nanbu earthquake), thin-walled hollow steel piers were common. Although some of these piers had concrete inll to prevent the local deformation of hollow tube caused by vehicle collision, the eect of the concrete inll was ignored in seismic design. Prior to the Kobe earthquake, thin-walled hollow piers were designed only for the Level 1 moderate earthquake with high probability of occurrence. In this design, the so-called seismic coecient method based on linear static analysis was employed within the frame work of allowable stress design (ASD), and no damage was permitted in piers (Japan Road Association, 1980). Owing to the small lateral seismic design force for the Level 1 earthquake, some thin-walled hollow steel piers were seriously damaged during the Kobe earthquake. From the lessons learned from the Kobe earthquake, the revised seismic design specications (Japan Road Association, 1996, 2002b, 2012b) introduced the concept of two-level seismic design. In this design, in addition to the conventional ASD for the Level 1 earthquake, the
10.1 Introduction ......................................................................................337 10.2 Types of Piers .....................................................................................338 10.3 Damages in 1995 Kobe Earthquake .............................................. 340 10.4 Structural Parameters ......................................................................343
