Retrofit yield spectra for the seismic upgrading of existing rc buildings

Abstract eng:
In the present paper, a new type of spectra, the Retrofit Yield Spectra (RYS), which provide direct insight into the implications effected by the selection of the design parameters on the definition of demand in terms of spectral acceleration and displacement at yield, is developed. The proposed methodology is based on predetermined controlled changes of the lateral response shape of vibration of the structure designed to eliminate localization of damage along the height of the building. To this end, a target response shape is selected depending on the type of the structural system and the identified deficiencies of the existing building. The target interstorey drift is achieved with a weighted distribution of added stiffness along the height of the building. Design of the seismic upgrading is performed in the elastic region, where stiffness is proportional to the flexural strength of reinforced concrete members. Thus, modification of stiffness is also accompanied by a commensurate change in the strength at yielding of the structural system.The Retrofit Yield Spectra (RYS) are inelastic design spectra on which curves that describe alternative retrofit scenarios have been superimposed. Depending on whether demand is expressed in terms of spectral acceleration, spectral displacement or interstory drift at yield of the first storey three alternative types are defined. For each retrofit scenario there is direct interrelation between demand in terms of spectral ordinates and design parameters. Derivation of the Retrofit Yield Spectra (RYS) is implemented in the casestudy of a RC building tested in full scale in order to examine the effectiveness of the proposed methodology.

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