Abstract Summary
The behavior of irregular bridges is more complex than that of regular systems, which is why some standards propose procedures or modification factors in the design of these structures are considered. Bridges can be irregular in their substructure (due to changes in stiffness and resistance of their elements) or in their superstructure (in curved and skew systems, or by changes in stiffness of their elements). Bridges with an irregular substructure in urban areas are generally defined to save other communication routes, so they usually have a longitudinal slope in their deck, which produces variation in the pier height. To understand the behavior of bridges with irregular substructure due to changes in their slope, six irregular models of reinforced concrete are analyzed, with slopes between 1° and 6°, which could be a maximum extreme value. The response of these models is compared with the response of a regular bridge with the same pier height, with a horizontal RC slab deck and AASTHO-type girders. All the models considered were designed to be located in three characteristic zones of Mexico City, defined as soft, intermediate and almost rigid soils. In the design, a real design truck and characteristic design spectra of the bridge location areas were assumed. From designs procedures, is defined the necessary information to elaborate models of the structures in the SAP-2000 program, considering that the structures are embedded. For each model, the dynamic characteristics of the bridges and their maximum responses are defined, in the form of displacements and mechanical elements in the piers. Also, normalized differences between the responses of irregular and regular systems are defined; these responses show the influence of every irregular condition. The analysis of the dynamic response of the bridges under study helps to understand how their periods and modal shapes change for different conditions of irregularity, which broadens the knowledge of these systems for a better design. The analysis of the maximum responses helps to understand the influence of different irregularity conditions, which could ultimately be considered in design standards. The obtained results are also compared with ones defined in highway bridges without slope but with changes in the length of their piers.
