Abstract:
The Taras overpass structure consists of 7 spans bridge with a total length of 250 m (750 ft) with precast prestressed concrete beams. Foundations were designed as drilled shafts of 1.2 m (3.9 ft) diameter and 36.0 m (118 ft) to 40.0 m (131 ft) length. Job site is in high seismic area of Costa Rica with an estimated median ground accelerations for the design earthquake (2475 yr PR) of 0.37g considering near fault effects. Lateral spreading or liquefaction were not considered in the initial stage of the project. The purpose of this study is to develop a set of recommendations to mitigate possible negative effects of lateral spreading for the structure performance. For this study, the equivalent nonstatic analysis developed by California Department of Transportation (CALTRANS) is used to evaluate lateral spreading. Site characterization was studied by MASW, CPT and PMT tests. Selection of geotechnical and structural modeling parameters are discussed as well as combining inertial demands with kinematic loads from lateral spreading considering recent studies. The results include parametric combinations of soil profiles and ground motions to account the sensitivity of the forces and deformations obtained for lateral spreading as well as recommendations to reduce the effects on the structure that can be implemented in the current construction stage at the time of this analysis.