Research On Seismic-isolating Effect Of FPS Bearing In Bridge Engineering

Bridge bearings which are used as key components of bridge structure stress,transfer load from deck to pier of bridge, and have to be adapt to live load, temperature,shrinkage of concrete, such as the change of external function. Rubber bearings have awide application in small and medium-sized bridges, but the slab rubber bearings do nothave energy consumption mechanism, its hysteresis curve is long and narrow, and theenergy consumption characteristics is poor. In addition, it circumscribes the applicationin bridge engineering because of the aging effects in natural environment. Although thelead core of rubber bearing has increased the energy consumption mechanism, earthquakeexcitation with low frequency characteristics of the small amplitude may amplify theearthquake response with core bearing system. Isolation effect is poorer to smallerstiffness of bridge pier. So the friction isolation system is valued. As the pure slidingisolation system does not have the restoring force and may produce larger residualdisplacement, it needs to combine with resilient components.Since Zayas, an American scholar, first proposed the concept which named FPSseismic isolation bearings, there have been large number of people undertaken a lot ofresearch on FPS bearing work, and have obtained some achievements. Recently, frictionpendulum isolation bearings(FPS) have been applied to some bridge engineering.Domestically, the most of present research work are the experimental studies, and thereports of theoretical analysis are rare.A numerical model was established for a continuous beam bridge with FPS bearings.It is based on Lagrange equations in dynamic mechanics. The software for its numericalsolution was presented with Newmark-β method. Calculation results show thatefficiency of the seismic isolation system is closely related to slipping friction factor onthe contacting surface and slide radius. The internal forces (shear forces) for piers exhibita significant reduction under an optimum combination of friction factor and slide radius.For friction factor being in the range of0.1-0.2and slide radius1.5m, the shear forcecould be decreased by more than50%, and the drift of beam would be less than10cm inhorizontal direction, most earthquakes recorded maximum horizontal displacement of nomore than3cm and less than0.3cm in vertical direction respectively. Also found that the piers weight changes did not affect the whole system; stringer weight change onlyincreases the pier shear, the isolation effect of the isolation system does not have animpact.