12/6/2012 Nonstructural Damage to Hospitals in Chile Nonstructural Damage to Airports in Chile Nonstructural Damage to Airports in Chile Damage in Recent Earthquakes desian codes is life-safety or c been subjected to fai Seismic Isolation Principles of Seismic Isolation 代运1 212/6/2012 2 Course Seminar, Tongji University, December 12, 2012 Photo by E. Miranda Ceiling-sprinkler head dynamic interaction Nonstructural Damage to Hospitals in Chile • 130 hospitals (71%) in Chile were affected, 18% of beds were lost • Damage to structural and nonstructural systems Photo by G.Mosqueda Course Seminar, Tongji University, December 12, 2012 Closeup view of some sprinkler heads sheared off Photo by E. Miranda Ceiling-sprinkler head dynamic interaction Nonstructural Damage to Airports in Chile • Damage to many types of nonstructural systems and equipment at Santiago airport led to closure of facility Photo by G. Mosqueda Course Seminar, Tongji University, December 12, 2012 Overall view of wood ceiling Photos by E. Miranda Ceiling-sprinkler head dynamic interaction Nonstructural Damage to Airports in Chile • Fire sprinkler damage/leakage in Conception airport led to flooding and closure of facility Course Seminar, Tongji University, December 12, 2012 Damage in Recent Earthquakes • A key objective of seismic design codes is life-safety or collapse prevention • There have been a few cases of structural collapse of modern buildings in recent earthquakes • In most cases, these structures have been subjected to fairly strong shaking • In performance-based design, objective is to limit overall losses • Large story drifts result in damage to structural system • Low to moderate story drifts can result in damage to nonstructural components such as partition • Large accelerations in structures result in damage to contents, piping and other mechanical equipment • Functionality of a structure following earthquake requires acceptable performance of both structural and nonstructural systems Course Seminar, Tongji University, December 12, 2012 Seismic Isolation • One of the most effective techniques to protect structures from EQ • Provides a flexible ‘isolation’ layer with lateral stiffness well below the structure lateral stiffness • Reduces natural vibration period of structural system • Limits energy transfer to structure reducing both accelerations and story drifts • Induces large displacement demands across the isolation interface • Requires specialized hardware that can provide large lateral displacement with vertical load capacity and re-centering capabilities Fixed - base structure Isolated Structure Image DIS-Inc Course Seminar, Tongji University, December 12, 2012 Principles of Seismic Isolation • Effect of period shift in seismically isolated structures • Reduction in seismic forces • Increase in lateral displacement demand of isolation system • Increased damping tends to improve seismic performance (Christopoulos and Filiatrault 2006)