Lecturer: Marios Panagiotou, Ph.D., PE
Seismic design of most buildings to modern code-minimum requirements aims to life-safety and a low probability of collapse. Such structures, especially at near-fault regions, are prone to significant post-earthquake damage, downtime, and costly repairs or demolition. I will present my analytical and experimental research as well as my engineering practice work on earthquake resilient buildings that sustain near-fault ground shaking and recover their functionality after a major earthquake without requiring cost-prohibitive repairs or excessive downtime. The presentation has three parts all summarizing corresponding parts of lectures of the Online Course on Earthquake Resilient Buildings .
Part I: summarizes the characteristics of very strong recorded near-fault ground motions, including their response spectra, in ten recent earthquakes (M6.2 to M7.6) and how these characteristics compare with the ASCE 7 description of seismic hazard of near-fault regions in Western U.S. The fault rupture process in recent earthquakes and how it affected structural damage at near-fault sites is also presented.
Part II: focuses on seismic design, analysis, and response of fixed-base RC wall and frame buildings at near fault-sites. Six buildings that range between 5- and 20-story tall are analyzed using 3D nonlinear response history analysis and the poor seismic performance of current ASCE 7 code-minimum designs is demonstrated. Key findings of the analysis are validated with the results of the tallest building ever tested on a shake-table in U.S. (7-story RC wall building slice) as well as with the large-scale tests of RC walls and beams. The conclusions of the analysis are further enhanced using the 3D nonlinear cyclic beam-truss-model that computes accurately and efficiently the deformation capacity of RC wall building systems including explicit computation of shear and buckling failures of RC walls. The reasons that minimum analysis requirements of ASCE 7 result in significant underestimation of displacements and forces are discussed and enhanced response spectrum analysis method that eliminates the underestimation is presented.
Part III: presents the analytical and experimental development of earthquake-resilient tall buildings (10- to 20-story tall) using base-isolation and low-damage rocking walls. The concept of low-damage rocking core-walls for tall buildings is introduced. These concepts are validated using 3DNLRHA in ETABS Ultimate and in Opensees. Based on the analysis results and the available experimental testing results of rocking components and isolation devices it is demonstrated that the construction of cost-efficient earthquake-resilient buildings (medium- and high-rise) at near-fault sites is feasible.