Giuseppe Gesualdi

Restoring capability of friction pendulum seismic isolation systems

The restoring (or re-centring) capability is an important feature of any isolation system and a fundamental requirement of current standards and guideline specifications for the design of seismically isolated structures. In this paper, the restoring capability of spherical sliding isolation systems, often referred to as friction pendulum systems (FPSs), is investigated through an extensive parametric study involving thousands of non-linear response history analyses of SDOF systems. The dynamic behavior of the isolation system is described with the visco-plastic model of Constantinou et al. (J Struct Eng 116(2):455–474, 1990), considering the variability of the friction coefficient with sliding velocity and contact pressure. Numerical analyses have been carried out using a set of approximately three hundred natural seismic ground motions recorded during different earthquakes and differing in seismic intensity, frequency content characteristics, magnitude, epicentral distance and soil characteristics. Regression analysis has been performed to derive the dependency of the residual displacement from the parameters governing the dynamic response of FPS. The influence of near-fault earthquakes and the accumulation of residual displacements due to real sequences of seismic ground motions have been also investigated. Finally, the restoring compliance criteria proposed in this study are compared to the lateral restoring force requirements of current seismic codes. Based on the results of this study, useful recommendations for a (more) rational design of FPSs are outlined.

Seismic Rehabilitation of Existing Reinforced Concrete Buildings with Seismic Isolation: A Case Study

The use of seismic isolation for the seismic rehabilitation of existing buildings is very attractive but often very tricky due to several aspects related to its implementation. In this paper, a case study of seismic rehabilitation of a high-rise residential building with seismic isolation is presented. The building under consideration is located in southern Italy and it is placed next to another building from which it is separated by a gap of 400 mm. In the paper, all the steps of the seismic rehabilitation process are described. First, the target objective of the seismic rehabilitation and the choice of isolation system type and location are discussed. The design of the isolation system, carried out following a direct displacement-based approach, is then examined. Finally, the main phases followed in the installation of the isolation system are described. Some comments on costs and time needed to complete the intervention are also reported.

Cost-benefit analysis of alternative retrofit strategies for RC frame buildings

ABSTRACT Monetary losses induced by earthquakes in Reinforced Concrete (RC) buildings are mainly due to damage to non-structural elements (infills, partitions, finishes, etc.). In this study, alternative retrofit strategies for reducing monetary losses in RC frame buildings are examined. They include local strengthening of infills (and partitions) and seismic isolation. The Expected Annual Loss (EAL) of a number of RC frame buildings, pre- and post-rehabilitation, is evaluated, following the time-based assessment approach proposed in the FEMA P-58 guidelines. The breakeven time of each retrofit intervention is then computed, considering the initial cost of the intervention and the expected benefit in terms of EAL reduction.

Developing Solutions Based on Shape Memory Alloys for Historical Constructions

The superelastic properties of Shape Memory Alloys (SMAs) can be used to improve the thermal and seismic behavior of steel tie-rods, which are often used in historical constructions. In this paper, a device prototype based on SMAs is presented, whose performances have been assessed through extensive experimental tests in thermal chamber and shaking table tests on reduced-scale testing models. The functioning principles of the device and the main steps for its implementation are first illustrated. The experimental behavior of the device is then examined. Finally, a recent example of application of the proposed technology to a historic single-aisle church, realized in the 13th century in Brindisi (southern Italy), and equipped with inadequate and deteriorated steel tied rods, is shown.