1. 1 Building Collapse Fragilities Considering Mainshock-Aftershock Sequences Using Publicly Available NEEShub Data Yue Li and Ruiqaing Song Michigan Technological University John W. van de Lindt The University of Alabama Nicolas Luco United States Geological Survey

2. Integration of Mainshock-Aftershock Sequences Into Performance-Based Engineering Using Publicly Available NEEShub Data John van de Lindt (Co-PI) University of Alabama Nicolas Luco (Co-PI) United States Geological Survey Yue Li (PI) Michigan Technological University Graduate Students: Ruiqiang Song Negar Nazari NSF CMMI -1000567

3. Introduction 3 During earthquake events, it’s very common to observe many aftershocks following the mainshock (588 aftershock with magnitude 5 and greater recorded after the Earthquake in Japan 2011). Tohoku Aftershock Although smaller in magnitude, aftershocks may have a large ground motion intensity, longer duration and different frequency content

4. Motivation 4 Potential to cause severe damage to buildings and threaten life safety even when only minor damage is present from the mainshock However, most of current seismic risk assessment focus on risk due to a mainshock event only February 2011 Christchurch Earthquake

5. Research Challenges Significant uncertainty in collapse capacity of damaged buildings after the mainshock Characteristics of aftershocks are quite complex Lack of system fragility models to evaluate building performance

6. P collapse = Seismic Rehabilitation of Existing Buildings

7. Tested Steel Structure at NEES @ Buffalo 7 A typical 4-story 2-bay steel moment frame (1/8 scale) is selected (Lignos and Krawinkler 2011)

8. Calibration of Prototype and Test model 8 Results Natural period in the EW directionPushover analysis in EW direction T1T2T3Peak based shear/weightMaximum roof drift Lignos Thesis1.320.390.190.28.2% Centerline model1.320.440.240.28.2% The first three modal periods, pushover curve, fragility curves and time history response of prototype and test model are calibrated

9. 2010 - 2011 Canterbury Earthquake Records at Resthaven, New Zealand 9

10. Structural Collapse Capacity 10 22 Far-Field records and 28 Near-Field records from FEMA P695 Preform incremental dynamic analysis (IDA) to determine structural collapse capacity

11. Damaged Building from Mainshock 11 In order to obtain the specific structural damage condition sustained from mainshock, the intensity level of mainshock is scaled to cause the following drift defined in ASCE/SEI 41-06 Damage LevelDrift Immediate occupancy0.7% transient life safety2.5% transient collapse prevention5% transient

12. Structural Collapse Capacity Difference Damage Level from Mainshock + Aftershock 12

13. Structural Collapse Capacity Difference Damage Level from Mainshock + Aftershock 13

14. Structural Collapse Capacity Mainshock Damaged Building + Different Aftershocks 14

15. Structural Collapse Capacity Mainshock Damaged Building + Different Aftershocks 15

16. Collapse Fragility Curves 16

17. Combination of Mainshock-aftershock Sequences 17 1.Mainshock + repeated aftershock (Far-Field) 2.Mainshock + random aftershock (Far-Field) 3.Mainshock (Far-Field) + aftershock (Near-Field) 4. As-recorded mainshock + aftershock sequences

18. Collapse Capacity for MS-AS Sequences 18

19. Summary and On-going Research 19 Damaged building from mainshock may have significantly reduced collapse capacity Structural collapse capacity depends on combination of mainshock - aftershock sequences, particularly the frequency contents in earthquake ground motions Investigation of portfolio of representative steel buildings Effects of as-record MS-AS sequences to be investigated Wood frame buildings – collaborative work at University of Alabama (Prof. John van de Lindt, Co-PI)

20. Thank you! Contact Information: Dr. Yue Li Associate Professor Michigan Technological University yueli@mtu.edu