Report - PEER - University of California, Berkeley

The survey stood on the condition that destructive damage occurred by adamaging earthquake in an urban area with over several thousands victims as well asseriously deteriorated functions in a wide range of area and facilities resulted byextensive damage of buildings, transportation facilities and utility facilities. Thequestions were directed to standard bridges, excluding special long bridges.SEISMIC PERFORMANCE LEVELSOne of the most important decisions in design is the levels of seismic performance.Six goals and levels as shown in Table 2 were shown to engineers to select two perengineer. Since there were engineers who did not reply or replied only one level,those were classified “no answer” in Table 2. Number of replies as well as crosscorrelation with the experience of 1995 Kobe earthquake, which will be describedlater, are presented in Table 2.Among six levels, Level 1 and Level 2 are a pair of questions. Level 2 intendsthat “it is allowed for engineers to design bridges so that collapse can be avoided nomatter how extensive damage which results in long suspension of traffic occursbecause it is not economically feasible to design bridges so that they do not sufferdamage under a rare earthquake such as the Kobe earthquake.” On the other hand,Level 1 intends that “since the roads and railways are essential infrastructures inurban areas, socio-economic damage (indirect damage) resulted by bridges damagemust be extensively larger than the direct damage. Furthermore, it takes weeks evento arrange materials and human resources once an urban area is extensivelydeteriorated by an earthquake. Therefore it is required to design bridges so that theydo not suffer extensive damage to an extent that they require emergency repair evenunder a rare earthquake such as the Kobe earthquake.”Excluding “no answer” (23.5%), Level 2 had the highest support of 23% from theengineers. This may be reasonable because Level 2 is now widely accepted in theengineering community worldwide. On the other hand, Level 1 had support of 14.5%.It is noted that the higher level of seismic performance in Level 1 had support ofnearly 2/3 of the support of Level 2.It is interesting to note that the support rate of Levels 1 and 2 depends on whetherthey experienced 1995 Kobe earthquake or not. If one classifies 100 engineers intotwo groups, i.e., the group who experienced Kobe earthquake (personally experiencedthe Kobe earthquake, involved in rescue and repair, or involved in design and analysisof damage bridges) and the group who did not experience Kobe earthquake, thesupport ratio for Level 1 was 17.9% in the group who experienced the Kobeearthquake, but it was only 10.6% in the group who did not experience the Kobeearthquake. This may be regarded that the engineers who have experienced Kobeearthquake intend to set higher seismic performance level than the group who did notexperience Kobe earthquake.The second highest support (15%) was directed to Level 6, i.e., “the seismicperformance level depends on the amount of investment. However it is civil engineers79