RUTHERFORD & CHEKENEOctober 9, 2010

PEER/NEES Column Blind PredictionModeling Approach

Background• Thanks:

• José Restrepo, Stephen Mahin, PEER, NEES• Great opportunity for practitioners• Benefit to our practice

• Colleagues: • Joe Maffei, Karl Telleen, Marko Schotanus,

Andreas Schellenberg

• Preliminary Model• SAP2000 v14.1

• Elastic frame element with cracked stiffness properties

• Two concentrated plasticity fiber hinges• 6 EQ run time 10 hours

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SeismoStruct Fiber Model• Force-Based Frame Element

(infrmFB)• 1 frame element• Unconfined cover concrete, confined core

concrete, longitudinal reinforcing materials• 700 fibers• 10 integration segments• Force-based element

• No discretization• Exact solution

• Global damping parameters

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Material Models• Unconfined Concrete (con_tl)

• Trilinear Concrete:• f’c = 6 kip/in2

• Ec = 4,400 kip/in2

• Confined Concrete (con_cc)• Mander Nonlinear Constant Confinement

Pressure Concrete:

• Peak Strain = ec = 0.003

• Mander Confinement kc = 1.2

• Longitudinal Reinforcing Steel (stl_mn)• Menegotto-Pinto Steel with post elastic buckling:

• fy = 75 kip/in2

• Transverse steel spacing and size

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Damping• Damping Model

• Rayleigh, mass proportional, stiffness proportional?• How much equivalent viscous damping, z?• Initial Stiffness, tangent stiffness?

• Previous Research on Bridge Piers• Sakai , 2007

• Failure: longitudinal bar buckling/fracture

• Elastic Response: z = 2% Rayleigh• Inelastic Response: z = 0.1% Rayleigh

• Priestley, 2007• Failure: longitudinal bar buckling/fracture• Damping: z = 2.0% tangent stiffness or no

elastic damping

• Lessons• Damping, materials, failure modes

RUTHERFORD & CHEKENEFrom Priestley et al, 2007

Ground Motions

• Time Series• Residual displacement

offset• Baseline correct?• Filter?

• Result• Minimal difference in peak

results

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0 10 20 30 40 50 60 70 80 90 100-0.6

-0.4

-0.2

0

0.2

0.4

0.6

Original Record

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Acc

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atio

n (g

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0 10 20 30 40 50 60 70 80 90 100-200

0

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Dis

plac

emen

t (cm

)0 10 20 30 40 50 60 70 80 90 100

-30

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-10

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30Original Record

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t (cm

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0.01 0.1 1 10 1000

0.10.20.30.40.50.60.70.8

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Frequency (hz)

Four

ier A

mpl

itude