Focusing on the load redistribution of statically indeterminate structures under mega earthquake motions, we investigated the ultimate behavior of the entire structure after a certain member reached its maximum load carrying capacity point. First, we newly developed a program that automatically builds a detailed entire bridge finite element model using shell elements, and outlined its concept. Next, the ultimate behavior of the upper-deck type steel arch bridge up to the safety limit of the entire system due to the damage accompanied by buckling of multiple members was analyzed by pushover analysis using an accurate shell element model. As a result, it was shown that there was a margin of about 1.4 times up to an entire structure reached the maximum load carring capacity after a certain member reached its load carring capacity.
