The abutments look discolored and older than the current superstructure. They may have been from an older bridge that deteriorated or had it's superstructure washed away by a flood.
The vertical members are attached to floor beams that support girders and the steel deck. The abutments include new shear keys.
Ecuador's Bridges: Puente Rio Sandima (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.