Seismic behavior of coupled column bridge RC piers: Experimental campaign

This paper focuses on presenting an experimental campaign devised at the Laboratory of Earthquake and Structural Engineering (LESE) of Faculty of Engineering of University of Porto (FEUP), and some of its earlier stage results. The scope of said campaign consists of exploring the seismic behavior of a double column reinforced concrete bridge bent frame with a short-spanned beam, which was designed to be applied on the construction of the Portuguese High-Speed Railway Line. As is the norm on HSRL bridges due to restricting code deformation limits, this particular application presents high stiffness to horizontal transverse loads. It is, therefore, predictable, that seismic demand on this bridge bent frame will be met with a structural performance associated with high shear load not only on the piers, but in the short-spanned beam as well, which can be a limiting factor on the global ductility achieved by the structure. In order to study this situation, reduced scale specimens were built, sharing a design goal of maximizing the shear ductility in the short-spanned beam. As such, the design approach was similar to that used in coupling beams of shear walls, for which several recommendations exist in the literature. Additionally, a new test setup is also presented, which was prepared at the LESE laboratory to accommodate the challenges of testing a frame structure under constant axial load and cyclic horizontal imposed displacements, on the specific context of this experimental campaign. The obtained results confirmed that shear ductility in the beams is a critical factor for the design of this type of structure, independent of the reinforcement layout, and that shear dominated failure is likely to occur, for lateral drift levels under 3.00%. Nonetheless, it also showed that specimens that adopt an adequate beam reinforcement layout for improved cyclic shear performance exhibit more than double the cumulative ductility of those that do not. In contrast, the columns were observed to experience relatively low damage outside the interface surfaces with the heavy shear damaged beams. (C) 2016 Elsevier Ltd. All rights reserved.