Report - PEER - University of California, Berkeley

It is interesting to clarify whether the experience of Kobe earthquake affected theestimate of expected repair period. In the group who experienced Kobe earthquake,the highest support was directed to “within a month” and “within a week” (both are20.8%), followed by “within 3 days” (17.7%), while it was “within 3 days” (29.8%)followed by “within a week” (27.7%) in the group who did not experience the Kobeearthquake. It seems that there is not essential difference on the estimate between thetwo groups.Actual Period for RepairTable 4 shows how the engineers evaluate the actual repair period. The highestestimate was “within a half year” (26%) followed by “within a month” (19%) and“within 3 months” (17%). It is noted that those actual repair periods are much longerthan the expected periods describe above.There exists an apparent difference on the estimate of actual repair perioddepending on the experience for Kobe earthquake. The top 3 estimate was “within ahalf year” (26.4%), “within 3 months” (24.5%) and “within a month” (18.9%) in thegroup who experienced the Kobe earthquake, while it was “within a half year”(25.5%), “within 3 weeks” (21.2%) and “within a week” (21.2%) in the group whodid not experienced Kobe earthquake. It is important to have not armchair theory butproper estimate on the repair period of structural members so that the seismicperformance levels can be appropriately determined in design.How Should We Account Realistic Demands on Repair Period in Design?If we are asked to design a bridge which can be accessed “within a week” and abridge which can be accessed “within 3 weeks” after the earthquake, how can we takesuch a difference of repair period into account in seismic design?Table 5 shows the results on how we can take account of two different demandson repair period. Although 22% and 15% replied that they can take account of thisdifference in design by differentiating residual drift after the earthquake and ductilitycapacity, respectively, majority (54%) replied that it was unable to consider such adifference based on the current design technology. We need a breakthroughtechnology which enables to incorporate such realistic demands in design.COST OF INITIAL CONSTRUCTION AND REPAIRIt is always the augments how much increase of initial cost can be validated forenhancing the seismic performance. Obviously, it is more costly to construct bridgeswith higher seismic performance. However if the cost increase is limited, engineersmay want to construct bridges with enhanced seismic performance. Arakawa andKawashima analyzed the dependence of construction cost on the intensity of lateralseismic force under various conditions (Arakawa and Kawashima 1986), and they83