Seismic Analysis of Large Buried Culvert Structures

Abstract

Field experience indicates that large buried culverts have suffered essentially no damage during past earthquakes when no significant permanent ground movements have occurred. These soil structures, which generally comprise steel or concrete arch members and engineered soil, may have spans of 15 m. Static, pseudodynamic, and dynamic finite-element analyses have been carried out on these structures and indicate that for horizontal seismic loading, the surrounding soil is much stiffer than the arch and results in the seismic load being taken by the soil rather than by the arch. Under vertical seismic loading, the arch is stiffer than the surrounding soil and attracts significant load, which can essentially be accounted for by increasing the unit weight of the soil in proportion to the vertical acceleration. Thrusts and moments in a 10-m concrete arch are examined under combined static and seismic loading (both horizontal and vertical). The results indicate that significant increases in thrust and moment in the arch are predicted for peak ground accelerations in excess of 0.3 g. The good behavior of these structures under such acceleration levels in California, where they are not specifically designed for earthquake forces, indicates that their static design includes sufficient reserve to prevent failure under accelerations of these levels.