Skypad Apartments Design Simulation Experimental Validation NEES@UCLA and the LAX Theme Building Seismic Retrofit and Restoration Bob Nigbor NEES@UCLA.
Download ReportTranscript Skypad Apartments Design Simulation Experimental Validation NEES@UCLA and the LAX Theme Building Seismic Retrofit and Restoration Bob Nigbor NEES@UCLA.
1 Skypad Apartments 2 Design Simulation Experimental Validation 3 NEES@UCLA and the LAX Theme Building Seismic Retrofit and Restoration Bob Nigbor NEES@UCLA 4 Project Team Scott Markle & David McCombs, LAWA Amir Gilani & Jaime Garza, Miyamoto Millard Lee, GWA Nato Flores, Tower & many others NEES@UCLA Staff: Steve Kang, Steve Keowen, Alberto Salamanca, Derek Skolnik, Ben Ferrero, Erica Eskes VCA Engineers Inc. CSA Constructors 5 OUTLINE • • • • History Restoration Project Unique Seismic Retrofit nees@UCLA’s Role 6 Los Angeles World Airports Theme Building Restoration THEME BUILDING RESTORATION 1 Events and Chronology 2/07 3/07 4/07 4/07 9/07 11/07 2/08 6/08 5/10 6/10 Events and Chronology 2/07 3/07 4/07 4/07 9/07 11/07 NEES@UCLA Tests 2/08 6/08 5/10 6/10 NEES@UCLA Tests Problems Encountered • • • • N S E Corrosion Observed Throughout Arches Existing Exterior Stucco Contained Asbestos Existing Primer Paint Contained Lead Seismic Deficiencies Discovered During Evaluation W Project Scope Demo and Reconstruct Core Walls, Remove and Reinstall Utilities from Core Walls Recoat (Repaint) Entire Building ADA improvements Reinstall Plaster Cladding on Upper and Lower Arches Structural Upgrades to Building Core, Including Tuned Mass Damper and Thru-Bolts Reinforce Perimeter Screen Walls and Foundations STRUCTURAL ANALYSES – SEISMIC AND WIND LOAD DESIGNS Seismic Analysis (Performance based) Wind Load Analysis Analyses Required for Cladding Design Los Angeles World Airports Theme Building Restoration STRUCTURAL ANALYSIS PROGRAM - SEISMIC Performance Based Design for Voluntary Seismic Retrofit • • • • Design is Based on FEMA, not IBC Range of Performance Levels extends from Immediate Occupancy to Collapse Prevention Collapse Prevention is the lowest level that protects the structure from collapse The structure will likely not be salvageable after a major earthquake, however, it should protect the lives of the occupants Seismic Upgrades – Tuned Mass Damper • • • • • • • Seismic Upgrades – Tuned Mass Damper Most Economical Solution Least Disruptive Alternative for Seismic Restoration Reduces Earthquake Forces 40% Proven Technology No Moving Parts to Maintain No Restaurant Closure Needed Retrofit Provides Collapse Prevention TUNED MASS DAMPER PROFILE 600 TONS OF STEEL ISOLATORS Los Angeles World Airports Theme Building Restoration DIS Linear rubber isolator bearing on new concrete pedestal and pad (8) Taylor Fluid viscous damper and housing (8) SEISMIC ANCHORING OF LAP SPLICES EXISTING Seismic strengthening of the core walls at three floor levels Los Angeles World Airports Theme Building Restoration REQ’D PROVIDED UPPER AND LOWER ARCH RECONSTRUCTION DECEMBER 2009 OCTOBER 2009 Los Angeles World Airports Theme Building Restoration NEES@UCLA: Advanced Dynamic Field Testing of Civil Structures http://nees.ucla.edu 29 nees@UCLA’s Role: Theme Building Experimental Modal Analysis (EMA) The LAX Theme Building is a uniquely difficult structure to model: Complex geometry Complex connections Older materials 2007 EMA measured in-situ modal parameters: frequencies, shapes, low & moderate-strain damping EMA added confidence to the modeling of earthquake and wind response of the pre-retrofit structure 2010 EMA confirmed post-retrofit condition & model accuracy TMD snapback test measured stiffness, frequency & damping of TMS system 30 Measurements UCLA’s “Mighty Mouse” shaker, with 10,000 lb maximum force, installed on east side of observation deck. Force kept small due to concerns about vibration levels, peak accelerations ~1%g. 51 channels of accelerometers installed at 18 locations Very high resolution digital recording to measure ambient through earthquake levels (micro-g to 2g) Pre-retrofit measurements in Fall 2007 Post-retrofit measurements in May 2010 31 Sensor Locations Shaker Location 32 Mighty Mouse Shaker 33 Sensor Recorder 34 Sample Data: Location 14, observation deck, vertical, 1-hour, ambient & shaking Peak~0.01g 35 Sample Data, Acceleration (g) Ambient Shaker Sweep Shaker at 2.6Hz 36 Sample Data, Displacement (inch) Ambient Shaker Sweep Shaker at 2.6Hz 37 Sample Ambient Vibration Spectra, Top of Core, X and Y Directions First Modes Dominate Core Motion 38 2007 Pre-Retrofit Results Frequency Shape Damping, Ambient Damping, Shaker 2.4 Hz N-S 1% 5% 2.6 E-W 2% 5% 4.7 Torsion + Legs 39 2010 Post-Retrofit Results Frequency Shape Damping, Ambient Damping, Shaker 1.8 Hz N-S 1% tbd 1.9 E-W 2% tbd 4.7 Torsion + Legs 40 Tuned-Mass Damper 90-Kip Snapback Tests 41 Great publicity for PerformanceBased Earthquake Engineering and NEES! 43 www.eqsymposium.com 44 QUESTIONS ? Impact of the TMD During Construction The crane is to lift 600 tons steel in multiple plates ~100’-0” above an active and occupied building Note: 600 tons = 200 Lincoln Navigators = 2 empty 747’s = 4 – story steel office bldg CORE RECONSTRUCTION Los Angeles World Airports Theme Building Restoration