This article proposes a numerical investigation of the frictional heating developed in sliding bearings under high velocities and the influence of the relevant temperature rise on the mechanical characteristics of the device. A three-dimensional finite element model of the bearing is created and frictional heat generation is modelled through a thermal source inserted at the sliding surface of the bearing, with intensity dependent on the coefficient of friction, the contact pressure and the velocity. The friction value is adjusted step-by-step on surface temperature and velocity and used to update the thermal flux and the resisting force developed by the bearing. The numerical predictions of temperature histories and force–displacement loops are compared with the results of laboratory tests to validate the numerical approach. The procedure can help in preliminary studies for the selection of bearing materials accounting for their thermal stability and for the estimation of change of design properties of sliding isolation bearings due to frictional heating.
1 March 2020 in Soil Dynamics and Earthquake Engineering
The paper illustrates an investigation on the effectiveness of dissipative bracing (DB) systems for seismic retrofit of buildings with sensitive non-structural components (NSCs) and technological content (TC), such as medical centers. The “Giovanni Paolo II” hospital, located in a high seismic prone area in Southern Italy, is chosen as case-study. The retrofit intervention with hysteretic braces is designed according to the Italian Building Code. The seismic response of the hospital building is investigated by means of non-linear history analyses carried out in OpenSees FE code and, in order to verify the full-operation after the earthquake, the integrity of NSCs and TC is checked. The retrofit design, thanks to the stiffening and damping effects introduced by DB system, proves suitable to protect both the structural frame and “drift-sensitive” non-structural components and content even under severe earthquakes (PGA = 0.45 g). Nevertheless, some concerns arise about the suitability of hysteretic braces for the protection of the “acceleration-sensitive” elements of the medical complex. Indeed, during weak earthquakes (PGA = 0.17 g), failures of several of these components are detected which can substantially impair the operation of the hospital in the aftermath of the seismic event.
1 April 2019 in Soil Dynamics and Earthquake Engineering