Stochastic Seismic Analysis and Comparison of Alternative External Dissipative Systems

Abstract

This paper deals with the seismic retrofit of existing frames by means of external passive dissipative systems. Available in different configurations, these systems allow high flexibility in controlling the structural behaviour and are characterized by some feasibility advantages with respect to dissipative devices installed within existing frames. In particular, this study analyzes and compares the performances of two external solutions using linear viscous dampers. The first is based on the coupling of the building with an external fixed-based steel braced frame by means of dampers placed horizontally at the floor levels. The second is an innovative one, based on coupling the building with a "dissipative tower," which is a steel braced frame hinged at the foundation level, and activating the dampers through its rocking motion. The effectiveness of the two solutions is evaluated and compared by considering a benchmark existing reinforced concrete building, employing a stochastic dynamic approach, under the assumption of linear elastic behaviour for the seismic performance evaluation. This allows efficiently estimating the statistics of many response parameters of interest for the performance assessment and thus carrying out extensive parametric analyses for different properties of the external systems. The study results provide useful information regarding the design and the relative efficiency of the proposed retrofit solutions.

The Seismic Retrofit by External Dissipative Systems: A Case Study

“…More details about the dynamic behaviour of external dissipative systems in the RB and FB configurations, can be found in [14] and [15] in the case of linear and plane structural systems.…”

“…In some recent studies, [14] and [15], the dynamic behaviour of frame structures coupled with external systems has been studied, accounting for the non-classically damped nature of the coupled system. In [15] a performance comparison between two external system configurations is done, first in terms of dynamic properties and then in terms of seismic response of different engineering parameters. However, these studies are limited to plane problems and linear behaviour of both the coupled system components.…”

Seismic Upgrading of a Historical Masonry Bell Tower through an Internal Dissipative Steel Structure

“…The idea of exploiting dissipative towers for the seismic upgrading of existing structures with deficient seismic performance is not new in structural engineering, e.g., [49][50][51], and some applications have recently been implemented in reinforced concrete buildings. The retrofit solution proposed in this article exploits fluid viscous dampers (FVDs), a class of dissipative devices widely used for passive seismic protection of both new and existing structures, which can be employed for improving the seismic response of structures by using either external or internal configurations [49,50,[52][53][54]. A real case study was considered (a historic masonry bell tower in Italy) and used as a testbed structure to evaluate the potentialities of the proposed approach.…”

A Design Method for Viscous Dampers Connecting Adjacent Structures

“…Also in (Impollonia and Palmeri, 2018) a similar system is investigated, but in this case, the external reaction towers have been equipped with non-linear devices. In (Gioiella et al, 2018b), a comparison was made in terms of efficiency between alternative external retrofitting systems, one consisting in a pinned-rocking truss with dampers at its base, and the other in a fixed base external structure with the dampers located at floor level. In (Reggio et al, 2019), the behavior of a primary structure protected by an external selfsupporting exoskeleton system, rigidly connected to the inner frame is assessed.…”