A design procedure of dissipative braces for seismic upgrading structures

Abstract

The research presented in this paper deals with the seismic retrofitting of existing frame structures by means of passive energy dissipation. An iterative displacement-based procedure, based on capacity spectrum is described and some applications are discussed. The procedure can be used with any typology of dissipative device and for different performance targets. In this work the procedure has been applied to an existing r.c. frame building, which shows both vertical and plan irregularities. In the application presented the buckling restrained braces have been used in order to prevent damages to both the structure and non structural elements. The evaluation of commonly Nonlinear Static Procedures (NSPs) for seismic response of the existing and retrofitted structure is presented to check the suitability of the use of NSP in the design procedure: the use of conversional NSPs to be not suitable for the case of irregular building but, once this building is retrofitted, and therefore regularized, with a bracing system, the use of NSPs for seismic response of the braced structure is effective.

Design of Dissipative Braces for an Existing Strategic Building with a Pushover Based Procedure

“…The procedure, that in previous works has been applied to retrofit building up to four stories [1,2] has been updated with the use of the multimodal pushover and successfully applied to a structure having eight floors (30 m height). The target displacement has been determined, both in longitudinal and transverse direction, for limiting both interstory drifts and ductility demand on existing structural elements.…”

“…impose a predefined loading pattern during pushover analyses. As discussed in Bergami and Nuti [1,2], the design of dissipative devices has two main goals: to improve dissipation and regularize strength end stiffness distribution by (this can be done adopting an adequate criteria to distribute the braces along the elevation and inside the plan of the building). Moreover, in case of medium rise building (quite widespread in Italy), it is a matter of fact that the relevance of higher modes not only depends on their level of irregularity but it is also related to the quite high number of stories.…”

Energy-Based Design Criterion of Dissipative Bracing Systems for the Seismic Retrofit of Frame Structures

“…Other approaches use equivalent linear or non-linear static analyses to evaluate the design actions and reduce their effects through added damping [40]. All the above-mentioned procedures are conceived for substantially regular structures.…”

Optimal Design of Tuned Mass Dampers by Performance–cost Analysis

“…In this field, many different strategies have been proposed also with regard to safety structural problems induced by random vibrations action caused by natural or artificial loads, as for example earthquakes, wind pressure, traffic vibrations, sea waves and so on [9][10][11][12][13][14][15][16]. Generally, four groups of control systems are distinguished in literature: Active, Hybrid, Semi-active and Passive.…”