Analysis of the dynamic properties of urban bridges with different slopes

Irregular bridges present more complex behavior than regular systems. A bridge is considered irregular when there are changes in stiffness or resistance in elements of the substructure, the superstructure or both, or when the higher modes have greater participation. Most of the previous studies consider irregular bridges with different height of piers and horizontal and straight superstructure. In this work, bridges with piers of different heights are analysed due to the presence of a longitudinal slope of the deck, which is more common for urban systems. The slopes considered range from 1% to an extreme 6%. With this information, elastic and inelastic models are generated with piers whose length gradually increases to achieve the slope. The bridges have equal-length four spans, simply supported, and three axes of single piers. The superstructure consists of a concrete slab and six AASTHO type beams. Responses of these bridges are compared with a regular model, with columns of equal height and without slope. For each structure, Ruaumoko code was used to create models. Typical vehicle load for Mexico is considered and bridges are located in three characteristic soil zones of Mexico City (firm, transition and soft). Results show that bridges with regular increment of the piers length have minor higher modes participation and a more predictable response.