Novel design procedure for steel hysteretic dampers in seismic retrofit of frame structures

An energy-based design procedure for sizing dissipative bracing systems equipped with steel hysteretic dampers is proposed for application to the seismic retrofit of frame structures. The procedure is based on the following assumptions: it is not iterative, as it provides a direct estimation of the steel dissipater sizes; the stiffening effects of dampers reduce displacements below prefixed limits; their damping effects reduce displacements and stress states to keep the response of structural members within their safe domains up to medium-to-high levels of the input seismic action. The procedure is articulated in three steps: seismic assessment analysis in current state and definition of the elastic properties of the bracing system to be installed in the structure; design of the dampers; verification of the seismic performance of the structure in retrofitted conditions. A demonstrative case study concerning a precast reinforced concrete frame school building is offered to explicate the practical application of the procedure, as well as to evaluate the enhancement of its response generated by the intervention. The latter consists in incorporating a dissipative bracing system equipped with triangular-shaped added damping and stiffness (T-ADAS) steel hysteretic devices. The two limit hypotheses assumed in the computational analyses for the roof beam-to-column connections of the building, i.e. hinges or fixed-ends, allow to discuss how the fundamental period of the structure in current conditions affects the parameters involved in the sizing process of the T-ADAS dampers.

Automated summary

This study proposes an energy-based design procedure for sizing dissipative bracing systems with steel hysteretic dampers for seismic retrofit of frame structures. The procedure assumes direct estimation of dissipater sizes without iteration, the stiffening and damping effects of dampers to reduce displacements and stress states, and safe response of structural members to seismic action. The procedure consists of seismic assessment analysis, design of dampers, and verification of seismic performance. A case study of a precast reinforced concrete frame school building is used to illustrate the practical application and evaluate the response enhancement generated by adding dissipative bracing system equipped with triangular-shaped added damping and stiffness (T-ADAS) steel hysteretic devices. Computational analysis considering different roof beam-to-column connection types is conducted to discuss the influence of the structure's fundamental period on the sizing process of T-ADAS dampers.