Pilotis buildings have widely spread out in developed countries since World War II onwards. From the structural point of view, Pilotis RC frames exhibit substantial lack in ductility capacity and shear resistance localized at the first floor, since they have been mainly realized before the seismic codes’ era. The present study shows the performance comparison of four advanced retrofit techniques when applied to typical Pilotis RC frame designed for gravity loads only according to Italian building code of ‘60s. A preliminary investigation has been performed to select non-linear numerical models suitable to describe the considered RC frame behavior, involving flexural inelastic hinges of RC beams and columns and in-plane axial inelastic hinges of masonry infill panels. Two seismic retrofit projects have been designed at a local level, by strengthening the masonry infilled panels with Fiber Reinforced Cementitious Matrix (FRCM) technique and alternatively by replacing infilled panels with prefabricated panels disconnected from the structure, so that no infill/frame interaction occurs. Two more retrofit projects have been designed at a global level, in order to improve the overall structural performance making use of energy dissipation and, alternatively, base isolation techniques. Nonlinear time history analysis and structural assessment have been carried out for the as-built case as well as for the four retrofit solutions according to Eurocode 8 and Italian Building Code, in order to highlight the structural deficiencies and relative improvements, respectively. Performances offered by the proposed retrofit techniques have been finally compared in terms of structural behavior, expected damage, and economic impact.

In the context of developing an innovative seismic dissipation system, which aims to compromise on the steadiness of friction and processes costs, this work deals with the tribological characterization of an S355JR structural steel, whose surface has been preliminarily treated by different mechanical and galvanic processes. Tribological tests were performed in a pin-on-disk configuration and in reciprocating motion, using values of 1 Hz and 2 Hz as the motion inversion frequency, a constant normal load of 50 N, and variable test duration, according to the most frequent seismic events. The tribological system was composed of S355JR structural steel pins and disks of the same steel, which were alternatively treated by electrolytic nickel plating, electrolytic zinc plating, and two different shot peening processes. The results highlight that while electrolytic nickel increments the overall steadiness of the coefficient of friction (COF), electrolytic zinc plating guarantees the longest first steady-state stage and a COF lower than the one guaranteed by the coupling of untreated pins and disk.

Over the past few decades, numerous precast reinforced concrete (RC) structures designed under outdated seismic codes have exhibited critical vulnerabilities. To enhance their seismic performance, this study examines a novel retrofit solution: the bidirectional rotational friction damper (BRFD). This passive energy dissipation device can function as both a connection and a damper in two orthogonal directions. The objective is to develop and validate a refined numerical model (BRFD-RNM) that accurately simulates the device’s bidirectional rotational friction behavior. The BRFD-RNM was implemented in OpenSees using flat slider bearing and elastic beam column elements, adopting a corotational transformation to reproduce circular motion. Experimental monodirectional and bidirectional tests conducted at the University of Bristol were used to calibrate and validate the model. The BRFD-RNM was then applied in a case study and compared with a simplified analytical model (BRFD-SAM) to assess the importance of modeling fidelity in capturing device–structure interaction. Results show that the BRFD-RNM effectively replicates experimental hysteresis behavior, especially when a velocity-dependent friction model is used. The inclusion of BRFDs in the frame significantly improves seismic performance, reducing interstory drifts by up to 64% and base shear by 25% without appreciably altering the structural configuration. While global structural performance is similar between the BRFD-SAM and BRFD-RNM, only the refined model captures critical local effects. These findings confirm the BRFD-RNM as a reliable and efficient tool for seismic assessment and retrofit design of precast RC structures and support its use in future blind predictions and shaking table validations.