Remarkable damage to non-structural elements and sometimes to structural members was surveyed in buildings retrofitted with dissipative bracing (DB) technologies recently hit by moderate-to-medium amplitude earthquakes. Damage is a consequence of the delayed contribution of protective systems to the seismic response of the buildings, caused by too high activation forces of dissipaters. In view of this, a sizing procedure for DB systems incorporating fluid viscous (FV) spring-dampers is implemented in this study. The procedure provides a simplified version of a recently proposed energy-based design criterion, and an extension of it by including a pre-evaluation of the activation force of the FV devices with respect to the normative Serviceability Design Earthquake (SDE)-related seismic demand. The sizing procedure is applied to the retrofit design of a demonstrative case study, represented by a school built in Italy in the early 1980s. Noticeable seismic vulnerabilities of the above-ground steel structure of the building are assessed in current conditions, highlighting local unsafety conditions of the profiles constituting the reticular steel columns starting from the SDE. A retrofit intervention consisting in the installation of a DB system equipped with FV spring-dampers is presented for the steel structure, designed by applying the proposed sizing method. The final verification time-history analyses confirm the activation of the FV devices at the SDE, and the attainment of the targeted elastic structural response up to the Maximum Considered Earthquake normative level.

Activation control extension of a design method of fluid viscous dissipative bracing systems

Sorace S.
2020

Abstract

Remarkable damage to non-structural elements and sometimes to structural members was surveyed in buildings retrofitted with dissipative bracing (DB) technologies recently hit by moderate-to-medium amplitude earthquakes. Damage is a consequence of the delayed contribution of protective systems to the seismic response of the buildings, caused by too high activation forces of dissipaters. In view of this, a sizing procedure for DB systems incorporating fluid viscous (FV) spring-dampers is implemented in this study. The procedure provides a simplified version of a recently proposed energy-based design criterion, and an extension of it by including a pre-evaluation of the activation force of the FV devices with respect to the normative Serviceability Design Earthquake (SDE)-related seismic demand. The sizing procedure is applied to the retrofit design of a demonstrative case study, represented by a school built in Italy in the early 1980s. Noticeable seismic vulnerabilities of the above-ground steel structure of the building are assessed in current conditions, highlighting local unsafety conditions of the profiles constituting the reticular steel columns starting from the SDE. A retrofit intervention consisting in the installation of a DB system equipped with FV spring-dampers is presented for the steel structure, designed by applying the proposed sizing method. The final verification time-history analyses confirm the activation of the FV devices at the SDE, and the attainment of the targeted elastic structural response up to the Maximum Considered Earthquake normative level.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11390/1187067
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