Evaluation of load distribution factors in prestressed bridges in México

Structural analysis for the design of bridges begins by determining actions acting on the structure, which are distributed through the superstructure, causing particular effects for each structural element of composition. Vehicle load is the main live action acting on the superstructure of a vehicular bridge. To estimate the distribution of this charge in the structural elements, different distribution models are used, which in its simplicity, they have limitations and restrictions for your application. Examples of these are the Courbon method and its variations, Homberg chart, standardized methods as coefficients AASHTO (American Association of State Highway and Transportation Officials), AASHTO LRFD (Load and Resistance Factors Design), Communications and Transport Secretariat (SCT by its Spanish acronym) standards, OHBDC (Ontario Highway Bridge Design Code) y CSA (Canadian Standard Association). The standardized methods mentioned above are mainly governed by a D-value defined by the geometric and material configuration of the bridge, as well as the specification of design load, which correlates the particular effects in the elements of the superstructure of these systems from of an analysis global, with the effects generated by one wheel line of load applied to an element particular in a particular analysis of the element. The criteria governing the structural design of bridges in Mexico is currently proposed by the SCT standards. Which has the criteria used in the AASHTO standards as a basis, it was developed for the specific conditions of the USA. This paper analyzes the principles and peculiarities of the above criteria, and presents the results of an analysis carried out for a particular structure using different criteria while proposing a methodology for the development of a model of load distribution in these systems, considering the specific conditions of Mexico.