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Seismic Behavior of Multi-Span Concrete Bridges with Link Slabs

Multi-span concrete bridges with simply supported girders are commonly used in short and medium span crossings. Such bridges are vulnerable to span separation at their expansion joints during earth¬quakes. In the previous earthquakes, many bridge superstructures have been fallen off their supports because of span separations. Such failures could be alleviated by replacing the expansion joints with link slabs. Link slabs are usually used in simply supported girder bridges in order to reduce or eliminate expansion joints and the problems associated with expansion joints. This paper presents the results of an analytical study on the seismic behavior and responses of multi-span concrete girder bridges connected by link slabs. In order to assess the responses of such bridges to seismic excitations, several bridges are analyzed by three dimensional finite element method. In this regard, both linear time history and response spectrum analysis methods are used in two directions; longitudinal and transverse. According to the results obtained in this research, in general, bridge natural period decreases and base shear increases in case of using link slabs rather than expansion joints. The seismic demands are signi¬ficantly reduced on the interior bents by replacing expansion joints with link slabs during transverse seismic excitation.