Experimental and Analytical Seismic Studies of a Two-Span Bridge System with Precast Concrete Elements and ABC Connections
AuthorBenjumea Royero, Jose Miguel
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Accelerated bridge construction (ABC) has gained acceptance as an alternative to conventional cast-in-place (CIP) construction. However, the lack of sufficient evidence that bridges incorporating precast elements and different ABC connections perform well under seismic loads has hindered and limited the application of ABC in high seismic regions. This gap was addressed in this investigation by designing, building, and testing under simulated ground motions a 0.35-scale, two-span ABC bridge model. Six ABC connection types were integrated in the bridge model: (1) column-to-footing connection, (2) column-to-cap beam connection, (3) girder-to-cap beam connection, (4) connection of deck panels from one span to the next at the pier, (5) deck-to-girder connection, and (6) connection between adjacent deck panels. The study comprised experimental and analytical investigations to assess the seismic performance of the bridge model and ABC connections under bi-directional horizontal earthquakes, determine the adequacy of existing design methods for the ABC connections and propose necessary refinements, determine the applicability of existing analytical tools to model ABC bridges and connections and formulate necessary improvements, and investigate potential effects on the bridge system and connections of parameters that were not included in the tests. The bridge model was subjected to eight successive ground motions with increasing amplitudes simulated on a shake table. The test results showed that ABC bridges can match the expected seismic performance of CIP bridges by exhibiting ductile response with sufficient energy dissipation and elastic behavior of the capacity protected members. The ABC connections performed well and maintained the integrity of the bridge model during the tests. Plastic hinges were formed in the columns, while the other bridge components remained undamaged. Design implications for the connections were evaluated and formulated based on their seismic performance. Extensive analytical studies using OpenSees software demonstrated that the displacements and base shears of ABC bridges can be estimated reasonably well by conventional and relatively simple modeling techniques. The parametric studies showed that vertical ground motions can induce substantial distresses in the superstructure-to-cap beam connections when the peak ground acceleration for the horizontal and vertical components are nearly synchronous.