COMPORTAMIENTO ESTRUCTURAL DE PUENTES URBANOS Y VIADUCTOS DE CONCRETO DESPLANTADOS EN TERRENO COMPRESIBLE

Abstract

Bridges and viaducts are subjected to considerable forces during strong ground motions that might cause major structural failures, damage and, in some cases they can lead to the collapse of the structure; for example the Loma Prieta, Northridge, Kobe and Chile earthquakes. Therefore, the performance of the viaducts is a particular interest of the structural behavior, response, bridge design and retrofit. In addition, the vehicular transport has increased in Mexico City in the last two decades and has caused an important traffic issue in the city. As an alternative to reduce this problem urban viaducts were adopted, although these types of structures represent complex structural systems. Also, it must be considered that the city located within a seismic zone with soft soil, in which ground acceleration are amplified, affecting the performance of many structures, such as bridges, making them vulnerable to damage in future earthquakes, for this reason, it is relevant to evaluate their seismic response and prevent its collapse. Then, this research is focused on the study of the structural behavior response of urban bridge and viaducts. For the structural analysis, RC frames that belong to the San Antonio viaduct were used; this structure is located in the soft soil zone of the Mexico valley. To determine the seismic response, the seismic simulation was done by numerical modeling with 3D non-linear analysis, considering :the geometrical and mechanical characteristics of the RC structure, as well as the soil-structure interaction effect using acceleration records during seismic events. This study was developed in two phases; during the first one, the numerical models assumes that RC frames columns are connected to a rigid foundation. In the second, the soil-structure interaction effect is incorporated to the model by using an equivalent stiffness in order to represent the soil characteristics of the Mexico valley. The structure is analyzed by a step-by-step dynamic analysis, with real and synthetic ground acceleration records registered in the Mexican Pacific coast, to get time-history data. Finally, from the numerical results obtained: the total inelastic deformations (drifts), the pattern failures and the sequential damage configuration in the structure, which are compared with current international and Mexican regulations.