Evaluations of different irregular conditions in bridges subjected to seismic load, considering systems with length relations of extreme girder to central girder of 1:0.25, 1:0.5, 1:0.75,1:1.25, 1:1.50, 1:1.75 and 1:2, and structures with curvatures of 30º, 60º, 90º, 120º, 150º and 180º, is analyzed in this paper. Seismic responses of irregular and regular (relation of lengths 1:1 and curvature of 0º) systems were obtained for maximum displacements and mechanics elements. The seismic loads used were a database of 53 seismic signals, recorded in stations located in one of the most hazardous zones of México. Elastic and nonlinear analyses were accomplished and the normalized differences between regular and irregular models were evaluated. This parameter was organized by quartiles to define trends of irregular bridge behavior ; Postprint (published version)