12/6/2012 Seismic Isolation Hardware Seismic Isolation Hardware-Elastomeric Raehsrdwaretoceamktoaoahasntymuradinsa30 erg Seismic Isolation Hardware-Elastomeric Seismic Isolation Hardware-Elastomeric Thin layers of rubber improve Seismic Isolation Hardware-Sliding Seismic Isolation Hardware-Sliding ogg ce to provide reemea F=a+μrgm( 7 3 12/6/2012 3 Course Seminar, Tongji University, December 12, 2012 Seismic Isolation Hardware • Reliable hardware for seismic isolation has only matured in last 30 years • Seismic isolation bearings require the following properties • Lateral flexibility relative to the structural system • Vertically stiff with ability to carry the gravity load under large lateral deformations • Sufficient initial stiffness to prevent relative motion under wind and other non-seismic loads • Two main types of seismic isolation bearings • Elastomeric bearings • Sliding friction bearings • Energy dissipation may be inherent in bearings, supplemental energy dissipation devices can be provided if not sufficient Mainly used in China Course Seminar, Tongji University, December 12, 2012 Seismic Isolation Hardware - Elastomeric • Elastomeric Bearings consist of alternating layers of steel and rubber • Lead Rubber bearings (shown below) include a lead core for enhanced energy dissipation • High damping rubber bearings Image DIS-Inc Course Seminar, Tongji University, December 12, 2012 Seismic Isolation Hardware - Elastomeric • Thin layers of rubber improve vertical stability of bearing Image T. Saito Course Seminar, Tongji University, December 12, 2012 Seismic Isolation Hardware - Elastomeric • Force-Displacement relationship for various types of elastomeric bearings • Shear strain defined as lateral displacement/total height of rubber (From Thompson et al. 2000) High Damping Rubber Lead Rubber Low Damping Scragging Course Seminar, Tongji University, December 12, 2012 Seismic Isolation Hardware - Sliding • Sliders on smooth flat surface that dissipates energy by friction with parallel linear springs to provide re-centering capabilities • Typically PTFE on polished stainless steel surface • Slider on concave surface to provide re-centering capabilities through gravity – Friction Pendulum bearing shown below Course Seminar, Tongji University, December 12, 2012 Seismic Isolation Hardware - Sliding • With Friction Pendulum Bearings, the structure displaces laterally similar to a pendulum, providing a re-centering force by gravity = Pendulum K2=W/R Friction QD=W