Report - PEER - University of California, Berkeley

who decide the design force levels and the performance goals. We make designcalculations according to design codes, but are we really trying to design bridges sothat damage can be avoided? We should deliver our engineering knowledge forpreventing damage.” This Level 6 was in pair of Level 5, i.e., “the seismicperformance depends on the amount of investment. Engineer’s mission is to do bestwithin a given investment and boundary conditions. Because budget is limited, it isdifficult to prevent extensive damage during destructive earthquakes such as the 1995Kobe earthquake.” Level 6 had slightly higher support than Level 5.It is interesting to note that the selection of Levels 5 and 6 also depends on theexperience of Kobe earthquake. Similar to the comparison of Levels 1 and 2, if weclassify into the group who experienced Kobe earthquake and the group who did notexperience the Kobe earthquake, the support ratio was 13.8% and 11.7 % for Levels 5and 6, respectively, in the group who did not experience Kobe earthquake, while itwas 13.2% and 17.9%, respectively, in the group who experienced Kobe earthquake.The fact that the support ratio for Level 6 is higher by 6.2% in the group whoexperienced Kobe earthquake than the group who did not experience Kobeearthquake shows the importance of strong involvement in determination of theseismic performance levels including appropriate investment level, instead of onlydoing our best within a given boundary condition.Expected Period for RepairEXPECTED AND ACTUAL REPAIR PERIODSHow soon bridges which had suffered damage by an earthquake can be repaired andre-accessed is one of the important decisions in the determination of seismicperformance levels. It was surveyed here from two points; one is the repair period inwhich bridges damaged are expected to repair after the earthquake (expected periodfor repair) and the other is the repair period which may be possible in the currentpractice after the earthquake (actual period for repair). The expected period for repairis shown below, and the actual period for repair will be discussed in the next section.Table 3 summarizes the expected period for repair of bridges. The highestsupport was directed to “within a week” (24%) followed by “within 3 days” (23%),“within a month” (14%), and “within 3 months (10%).” Few supported “immediate,i.e., damage which requires repair should not be allowed” (2%) and “within a halfday” (5%).Actual repair period was long after Kobe earthquake. For example, whencolumns failed in shear and a plate girder deck suffered buckling at web plates andlower flange plates near the supports, it took 3 weeks to temporarily confine thecolumns by new reinforced concrete and to shore up the deck. It took weeks forsurvey and design, and it took months to fabricate structural members. Stock ofstructural members for replacement, such as bearings and expansion joints were notavailable. It should be noted if damage occurred at only a bridge, temporary shoring81