Partial Isolation as a Design Alternative for Pile Bent Bridges in the New Madrid Seismic Zone

Abstract

AbstractPile bent bridges are a frequently chosen solution for stream crossings in the New Madrid Seismic Zone (NMSZ). Ease of construction makes the pile bent bridge a favorable choice in challenging subsurface conditions. When seismic loading requires conventionally constructed pile bents to behave in an inelastic fashion, the wall thickness of unfilled steel pipe piles necessary to preclude local buckling virtually doubles relative to that required if the piles remain elastic. Partial isolation—in which isolators are located at the piers with the abutments constructed integrally—is proposed as a strategy deserving of consideration for such situations. If piling can be designed to remain elastic, then the savings in material costs will, at least partially, offset the cost of isolation bearings. Along with isolator displacement demands, the yield strength necessary to keep the piles in the elastic range is a key parameter to be determined.