Influence of the use of external shear keys on the seismic behavior of Chilean highway bridges

The present study evaluates the influence of external sacrificial shear keys on the seismic behavior of bridges commonly found in Chile. The damages observed in the external sacrificial shear keys as a result of the Maule earthquake of 2010 led to the revision of this type of elements. The results of a statistical analysis of Chilean highway bridges were used to identify a representative typology of bridges. Two models were used for the evaluation of the seismic behavior of the selected typology, given different soil conditions and seismic hazard zones, as follows: (1) one without sacrificial shear keys, which has no transverse displacement restriction and (2) other with non-linear shear keys, which offers transverse constraint to displacement up to a maximum deformation of the sacrificial shear key. Fragility curves were generated using non-linear analytical models and a series of compatible records. The comparison of the fragility curves for damage levels I (initial slip) and II (large residual displacement of the superstructure) shows that the most vulnerable bridges are bridges without external shear keys, regardless of the seismic hazard zone and the type of soil. For damage level III (collapse) it is irrelevant whether or not the bridge has external shear keys.