A negative stiffness reinforced concrete system for resilient seismic design

Abstract

This paper presents cyclic tests of 1:5 scale restrained rocking RC columns exhibiting negative stiffness. The proposed recentering system can be used for the seismic design of resilient bridges. Negative stiffness leads to a reduction of the design moments of both the superstructure and the foundation, compared to fixed base or restrained rocking systems of positive stiffness. Moreover, the suggested design method, allows for the precasting of the substructure and easy assemblage on-site, therefore reducing on-site construction time, and consequently traffic impact. Cyclic tests were carried out on a reinforced concrete column allowed to rock on its interface with the foundation and cap-beam. An unbonded tendon was used to restrain the column. The tendon was connected in series to a disc (“Belleville”) spring system so that the overall postuplift stiffness of the system stays negative. Steel plates were introduced at the ends of the columns to protect them from stress concentrations. The tests results show that the column returned to its original position with negligible to no residual displacement, even when tilted to 15% drift ratio.