PEER Van Nuys Testbed

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FEMA 356 Evaluation

• PEER Van Nuys Testbed
• May 23, 2002
• by Jon Heintz, S.E. Robert Pekelnicky

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Van Nuys Holiday Inn
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Van Nuys Holiday Inn

• Designed in 1965 Constructed in 1966
• Seven Stories, 65 Height
• 150 x 61 Approximate Plan
• Non-Ductile Exterior Concrete Frame
• Interior Slab-Column Frames
• Masonry infill in four bays
• Building Instrumented

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Typical Floor Plan
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Exterior Frame Elevation
North Elevation
South Elevation
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Evaluation Methodology

• Perform ASCE 31 (FEMA 310) Tier 1 screening.
• Create 3-D linear dynamic model.
• Determine Modes Periods
• Evaluate Torsion
• Perform 2-D nonlinear pushover of longitudinal
  exterior and interior frame.

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Tier 1 Deficiencies

• Soft First Story (44 of 2nd story)
• Quick Check Column Shear gtgt Capacity
• Members Shear Controlled
• Weak Column / Strong Beam (Mc0.8Mb)
• Inadequate Lap Splices
• Minimal confinement reinforcement
• Stirrups Ties w/o seismic hooks

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3-D Model
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Elastic Model Assumptions

• Concrete strength fce 150 of specified
• Frame beams modeled with ACI effective slab
  widths
• Interior flat slabs modeled as effective beams
  (Luo et. al. 1994, Pecknold 1975)
• Effective stiffnesses used
• Columns 50 of Gross (FEMA 356)
• Beams 50 of Gross (FEMA 356)
• Slabs 33 of Gross (Vanderbilt 1983)
• Beam-Column Joints partially rigid
• Columns fixed at pile cap

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Transverse Fundamental Mode
T 1.27 sec. PMR 85
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Longitudinal Fundamental Mode
W/O Infill T 1.20 sec. PMR 89 W/ Infill T
1.12 sec. PMR 77
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Plan Torsion Fundamental Mode
W/O Infill T 1.03 sec. PMR 0 W/ Infill T
1.00 sec. PMR 8
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Comparison with Recorded Periods (longitudinal)

• Pre-1971 T0.52 sec
• San Fernando
• early T0.7 sec
• peak response T1.5 sec
• Northridge
• early T1.5 sec
• Elastic model
• FEMA 356 empirical equation T0.73 sec
• T1.2 sec w/o infill

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Plan Torsional Irregularity

• Torsion triggers amplified target disp.
• Infill has 1 expansion gap between frame.
• Two models used one with infill panels and one
  without infill panels.
• Models compared to determine whether presence of
  infill has dramatic effect.
• 3-D model results did not trigger ?
• 3-D model results did not show significant
  response modification for higher modes

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2-D Nonlinear Pushover

• Model longitudinal direction as critical
• Include both exterior and interior frames.
• 2 exterior frames 40 of stiffness
• 2 interior frames 60 of stiffness

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2-D Nonlinear Pushover

• Place hinges at all member ends
• Use criteria in FEMA 356 for hinge properties
• Flexural hinges limited by
• flexural strength
• shear strength
• lap splice strength
• embedment (development)
• Include two load patterns
• Uniform based on floor mass
• Modal based on CQC combination of Modes

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Pushover Curves
Target dt 29 inches (10/50) Target dt 7
inches (50/50)
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Hinge locations

• Flexural hinges at base of columns (lap-splice
  controlled)
• Flexural hinges below 2nd floor beams
• Shear controlled hinges in 1st, 2nd, 3rd floor
  beams
• Still need to check
• shear in columns
• shear in joints
• local hinge rotation limits
• slab punching shear on interior frames

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Response Spectra
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Roof Displacement

• Peak displacement during Northridge
• 9.2 inches
• Calculated displacement capacity is significantly
  less. Why?
• Conservative hinge assumptions? (actual elements
  can go farther)
• Conservative limitations on lap splice
  capacities?
• Conservative accounting for degradation (C3)
• Higher Mode Effects? (not a factor based on our
  linear model results)
• Plastic hinge not a reliable EDP?

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Summary

• ASCE 31 Tier 1 does a good job of predicting
  possible deficiencies
• FEMA 356 does reasonable job of predicting
  cracked stiffness, in lieu of more detail
• FEMA 356 NSP yields very conservative results for
  this building
• Can PEER Methodology more accurately predict
  recorded response?