University of Illinois Contribution on Analytical Investigation

Amr S. ElnashaiSung Jig KimCurtis Holub

Narutoshi NakataOh Sung Kwon

Outline

Introduction

Analysis Tools

Effect of Vertical Ground Motion on Piers

Assessment of Bridge with Skewness

Considering Torsional Effect on RC Piers

Advanced Bridge Analysis with Soil-Structure

Interaction

Future Work

Introduction

Analytical Focus

Analysis of a series of bridge structures subject to different levels of earthquake excitations – DIANA, OpenSees, and Zeus-NL- the MAE Center advanced analysis

platform– The unique features of each FE application will be combined as

distributed computational simulation using UI-SIMCOR as a simulation coordinator

– Analytical work will provide the modeling of PSD conditions to zoom on parameters resulting in high levels of simultaneous horizontal and vertical accelerations.

Study the seismic response of the bridge systems, including foundations and surrounding soils– Appropriate multidirectional loading and boundary conditions for

columns can be obtained

Determination of the appropriate input loading for the specimens tested in the subsequent phases of the project

Analysis Tools

FE applications

• Nonlinear frame analysis, nonlinear hysteretic concrete model, meshed section, freely available

• Open source application, soil modeling

• 2 and 3-D modeling of reinforced concrete structures

UI-SimCor– Simulation coordinator for the distributed computational

simulation– Combine unique features of each application

Analysis Tools

UI-SimCor

Simulation overview

Tested Structure

UI-UI-SIMCORSIMCOR Disp.

Force

Soil & Foundation Module

(OpenSees)

Disp.

Force

Structural Module

(Zeus-NL)

Multi-Platform Simulation Framework

Key components of implementation– PSD test integration scheme: α-OS method– Sub-structuring technique– Communication between each modules– Hardware for physical testing

UI-SimCor

AP

IA

PI

Equipments

Component n

Simulation Coordinator Component 1

MDL 1

Object 1 of MDL_RF class

Simulation Monitor

Clie

nt

DO

F M

appi

ng

MDL n

Object n of MDL_RF class

Simulation Monitor

Clie

nt

AUX

Objects of MDL_AUX classC

lient

Stiffness Evaluation

Static Equilibrium

Dynamic Equilibrium

Simulation Control

Main Routine

Disp.

Force

DAQ

Camera

TC

P/I

P N

etw

ork

Ser

ver

Ser

ver

Ser

ver

AP

I

Framework architecture

Multi-Platform Simulation Framework

Effect of Vertical Ground Motion on Bridge Pier

Parametric Study with Simple Model

ParametersParameters– Five equal spans with each span length varying 10m to 50m– Variable span (5 cases): The ratio of the length of first span to that of

second span is changed from 0.2 to 1.0– Variable column height (5 cases): 4 m to 12 m

Ground motions recorded at 6 stationsGround motions recorded at 6 stations 6 combinations of components for each EQ record6 combinations of components for each EQ record

– L, T, L+T, L+V, T+V and L+T+V– L: longitudinal GM, T: Transverse GM, V: Vertical GM

H

L2 L1

Pier Section

Parametric Study with Simple Model

Axial force is mainly affected by vertical ground motionAxial force is mainly affected by vertical ground motion– Especially, as span ratio increase, the effect of vertical seismic motion to axial

force increase significantly only when vertical record is considered Shear capacity is reduced by vertical ground motion Shear capacity is reduced by vertical ground motion

– Span length is longer – Span ratio is close to 1 – Column height is shorter– In case of seismic assessment for the structure with above geometric

configurations, vertical ground motion should be considered

0

500

1000

1500

2000

2500

3000

3500

0 0.2 0.4 0.6 0.8 1 1.2

Span Ratio

Var

iati

on

of

Axi

al F

orc

e (k

N)

L

T

LT

LV

TV

LTV

-5000

-4000

-3000

-2000

-1000

0

1000

6 8 10 12 14 16

Time (sec)

Axia

l F

orc

e (

kN

)

L

LT

LTV

Axial force Axial force variation

LV and L

-50

-40

-30

-20

-10

0

10

0 10 20 30 40 50 60

Span Length (m)

Incr

easi

ng

Rat

io o

f S

hea

r C

apac

ity(

%)

Northridge-Arleta Fire Northridge-Santa Monica KOBE-Port Island Array KOBE-Kobe Univertsity LOMA Prieta-Corralitos Loma Prieta-Capitola

4 6 8 10 12 140

500

1000

1500

2000

2500Horizontal Motion

Time (sec)4 6 8 10 12 14

0

500

1000

1500

2000

2500Horizontal and Vertical Motion

Time (sec)

Sh

ear

Fo

rce

(kN

)

Shear DemandShear Capacity

Shear DemandShear Capacity

Sh

ear

Fo

rce

(kN

)

4 6 8 10 12 140

500

1000

1500

2000

2500Horizontal Motion

Time (sec)4 6 8 10 12 14

0

500

1000

1500

2000

2500Horizontal and Vertical Motion

Time (sec)

Sh

ear

Fo

rce

(kN

)

Shear DemandShear Capacity

Shear DemandShear Capacity

Sh

ear

Fo

rce

(kN

)

HGMHGM VGMVGM Increasing ratio ofIncreasing ratio of V due to VGMV due to VGM

Summary

Complex Straight Bridge

Prototype Structure– Collector-Distributor 36 of the Santa Monica (I10) Freeway– Significant damage by Northridge earthquake (1994)

Model Structure– The bridge is assumed to have three piers– The initial loads applied to the top of piers as deck self-weight

6 earthquake records used in parametric study were selected

10106655 77 88 99

Expansion JointExpansion Joint

Rectangular Wall Rectangular Wall

(B=457, H=9000)(B=457, H=9000)Circular Pier (D=1219)Circular Pier (D=1219)

Circular Pier (D=1219)Circular Pier (D=1219)Circular Pier (D=1219)Circular Pier (D=1219)

474047402721527215 1896018960 3226032260 3079530795 1387513875

127751277555

60856085 65756575 62906290 59455945

Layout of Santa Monica Freeway (unit, mm)Layout of Santa Monica Freeway (unit, mm)

27.215 m 23.700 m 32.260 m 30.795 m

6.085 m6.575 m 6.085 m

Layout of Model StructureLayout of Model Structure Pier 1Pier 1 Pier 2Pier 2 Pier 3Pier 3

Initial loadInitial load 2288.822288.82 2515.622515.62 2834.562834.56#4 Stirrups @ 406mm cs.

24-#11 for the outer bars8-#11 for the inner barsTotal: 32 - #11

12

19 m

m

50.8mm cover

• ConcreteConcrete- ,- ,

• Reinforcement barReinforcement bar- ,,

- Initial load (kN)Initial load (kN)

' 234.5 N/mmcf 32500 kg//mc

2413 N/mmyf 37850 kg//ms

Modeling and Consideration

Complex Straight Bridge

-5

0

5

10

15

20

25

30

0 0.5 1 1.5 2

V/H Ratio

Rat

io o

f P

erio

d In

crea

se (

%)

Northridge-Arleta F.Northridge-Santa M.Kobe-Port I.A.Kobe-Kobe Univ.Loma P.-CorralitosLoma P.-Capitola

-5

0

5

10

15

20

25

0 0.5 1 1.5 2

V/H Ratio

Rat

io o

f P

erio

d In

crea

se (

%)

Northridge-Arleta F.Northridge-Santa M.Kobe-Port I.A.Kobe-Kobe Univ.Loma P.-CorralitosLoma P.-Capitola

Period change by V/H ratioPeriod change by V/H ratio

Vertical period of vibrationVertical period of vibrationHorizontal period of vibrationHorizontal period of vibration

Variable V/H ratios– A fixed time interval and PGA of horizontal ground motion– 16 V/H ratios per earthquake record are considered

• Range of 0.5 to 2.0 with an increment of 0.1

Effect on the periods of vibration– The period is elongated for both components as the vertical amplitude increases– The slope of rate of period increase is steeper up to a V/H Ratio of 1.0

Effect on Axial Force and Shear Capacity– Axial force variation increases as V/H ratio increases– Shear capacity is reduced by 5% to 36%

-40

-35

-30

-25

-20

-15

-10

-5

0

0.5 1 1.5 2

V/H Ratio

Cap

acit

y In

cre

asin

g R

ati

o (

%)

Northridge-Arleta FireNorthridge-Santa MonicaKOBE-Port Island ArrayKOBE-Kobe UnivertsityLOMA Prieta-CorralitosLoma Prieta-Capitola

Increasing ratio of shear capacity by VGMIncreasing ratio of shear capacity by VGM

0

10

20

30

40

50

60

70

80

90

100

0.5 1 1.5 2

V/H Ratio

Co

ntr

ibu

tio

n o

f V

GM

to

axia

l fo

rce (

%)

Northridge-Arleta FireKOBE-Port Island ArrayNorthridge-Santa Monica LOMA Prieta-CorralitosKOBE-Kobe UnivertsityLoma Prieta-Capitola

Contribution of VGM to axial force variationContribution of VGM to axial force variation

Effect of V/H Ratio

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

2 4 6 8 10 12 14 16

Monitoring Time (sec)

Per

iod

(se

c)

TimeLag 0

TimeLag 0.5

TimeLag 1.0

TimeLag 1.5

TimeLag 2.0

TimeLag 2.5

TimeLag 3.0

TimeLag 3.5

TimeLag 4.0

TimeLag 4.5

TimeLag 5.0

VPG_time

Horizontal period of vibration, Kobe (port Island)Horizontal period of vibration, Kobe (port Island)

Complex Straight Bridge

Variable time interval– Range 0.0 to 5.0 sec with an increment of 0.5 sec (11 cases)– This is accomplished by shifting the HGM along the time axis– The original recorded V/H ratios are fixed

Effect on the period vibration and Shear Capacity– The horizontal period is more elongated when the time interval is small– The shear capacity tends to increase slightly as the arrival time interval increases

-50

-40

-30

-20

-10

0

10

20

30

40

50

0 1 2 3 4 5

Time Interval (sec)

Cap

acit

y In

crea

sin

g R

atio

(%

)

Northridge-Arleta FireNorthridge-Santa MonicaKOBE-Port Island ArrayKOBE-Kobe UnivertsityLOMA Prieta-CorralitosLoma Prieta-Capitola

Increasing ratio of capacity by VGMIncreasing ratio of capacity by VGM

Effect of Time Interval

Torsional Effect on Bridge Pier

Proto-type BridgeFHWA No.4 Skew Bridge (FHWA-SA-97-009, 1996)

Parametric Study with Various Skew Angles

1st Mode: LongitudinalF1 : 1.99 (Hz)

2nd Mode: TransverseF2 : 2.40 (Hz)

3rd Mode: RotationalF3 : 2.96 (Hz)

4th Mode: BendingF4 : 3.34 (Hz)

30

Fundamental Vibration Modes

Parametric Skew Angles

0 ,15 ,30 ,45 ,60

Effect of Skew on Natural Frequencies

Up to 30 degree, effect of

skew angle is slightly

small on the fundamental

frequencies.

Effect is more significant

on deck bending modes

than any other modes.

0 15 30 45 601.5

2

2.5

Skew Angle (degree)

Fre

quen

cy (

Hz)

Longitudinal Mode

0 15 30 45 602

2.5

3

Skew Angle (degree)

Fre

quen

cy (

Hz)

Transverse Mode

0 15 30 45 602

2.5

3

3.5

4

Skew Angle (degree)

Fre

quen

cy (

Hz)

Rotational Mode

0 15 30 45 602

3

4

5

6

Skew Angle (degree)

Fre

quen

cy (

Hz)

1st Bending Mode

0 15 30 45 602

3

4

5

6

Skew Angle (degree)

Fre

quen

cy (

Hz)

2nd Bending Mode

0 15 30 45 604

4.5

5

5.5

6

Skew Angle (degree)

Fre

quen

cy (

Hz)

3rd Bending Mode

SR1.2-1.2

SR1.6-1.6

SR2.0-2.0 SR1.2-2.0

SR1.2-1.6

SR1.6-2.0

1/1.2 1/1.21

1/1.6 1/1.61

1/2.0 1/2.01

1/1.2 1/1.61

1/1.6 1/2.01

1/1.2 1/2.01

: :

: :

: :

: :

: :

: :

Pier 1

Pier 2

Pier 3

Pier 4

Parametric Study with Span Length Ratios

Symmetric Span Ratios Asymmetric Span Ratios

Parametric Model Span Length Configurations

1.5

2

2.5

SR

1.2-

1.2

SR

1.6-

1.6

SR

2.0-

2.0

SR

1.2-

1.6

SR

1.6-

2.0

SR

1.2-

2.0

Longitudinal Mode

Fre

quen

cy (

Hz)

2

2.5

3

SR

1.2-

1.2

SR

1.6-

1.6

SR

2.0-

2.0

SR

1.2-

1.6

SR

1.6-

2.0

SR

1.2-

2.0

Transverse Mode

Fre

quen

cy (

Hz) Straight

Skew

2.5

3

3.5

SR

1.2-

1.2

SR

1.6-

1.6

SR

2.0-

2.0

SR

1.2-

1.6

SR

1.6-

2.0

SR

1.2-

2.0

Rotational Mode

Fre

quen

cy (

Hz)

2

3

4S

R1.

2-1.

2

SR

1.6-

1.6

SR

2.0-

2.0

SR

1.2-

1.6

SR

1.6-

2.0

SR

1.2-

2.0

Bending Mode

Fre

quen

cy (

Hz)

Effect of Span Length Ratios

Rotational and Bending

modes are sensitive to the

variation of span length

ratios.

Effect of the skew angle in

any span length ratio

configuration are negligible

on the natural frequencies.

SR1.2-1.2 SR1.6-1.6 SR2.0-2.0 SR1.2-1.6 SR1.6-2.0 SR1.2-2.00

1

2

3

Rat

io (

degr

ee /

m)

Pier

1Pi

er 2

Pier

3Pi

er 4

StraightSkew

Effect of Span Length Ratios

Symmetric Span Ratios Asymmetric Span Ratios

Torsional / Transverse Ratio in Transverse Mode

In symmetric span length configurations, torsional effect on any piers are somewhat similar

regardless of skew angle.

With skew angle and asymmetric span length configuration, torsional effect in fundamental modes

can be significantly different depends on the location of the piers.

Torsional effect is higher than any other piers in any configurations.

Torsional Effect on RC Piers

Selection of Bridge Configurations

1/1.2

1/1.2

1

Case 1Skew Angle: 0 (degree)Span Length Ratio: 1/1.2 : 1.0 : 1/1.2

1/1.2

1/1.2

1

Case 2Skew Angle: 30 (degree)Span Length Ratio: 1/1.2 : 1.0 : 1/1.2

Case 3Skew Angle: 30 (degree)Span Length Ratio: 1/1.2 : 1.0 : 1/2.0

1/2.0

1

1/1.2

In order to see the effect of skew angle, two bridge configurations, straight and 30 degree skew

angle, are selected for further detail study. For the evaluation of extreme torsional effect within regular bridge category, configuration with span

length ratio, 1/1.2-1.0-1/1.2, is also selected for further study.

Advanced Bridge Analysis with Soil-Structure Interaction

Advanced Bridge Analysis with SSI

Effect of soft soil deposit on structural response

– Ground motion amplification

– Structural period elongation

– Radiational and hysteretic damping

– Permanent soil deformation

Bedrock

Soft Soil

– SSI, detrimental or beneficial.…?

– Displacement redistribution

– Force redistribution

– Input motion change

Neglecting SSI can be highly

inaccurate

Background

Introduction – MRO Bridge

Meloland Road Overcrossing Bridge

26 139

75

3 11

24

Wing wall and abutmentEmbankment

Timber pile foundation

Accelerometer channel #

Meloland Road Overcrossing

Imperial Fault

Brawley Fault Zone

0 10 20 40 60

Kilometers

Meloland Road Overcrossing

Imperial Fault

Brawley Fault Zone

0 10 20 40 60

Kilometers

Introduction – MRO Bridge

Recorded Ground Motions

IDDate

yr/mo/dyML Lat Long Depth (km) Epic. Dist. (km) PGA (g) Available record1

GM01 79/10/15 6.6 32.614 115.318 12.1 21.5 0.3 B

GM02 99/10/16 7.1 34.594 116.271 6.0 216.0 0.016 D

GM03 00/04/09 4.3 32.692 115.392 10.0 10.4 0.043 B, D

GM04 00/06/14 4.2 32.896 115.502 5.1 14.6 0.015 B, D

GM05 00/06/14 4.5 32.884 115.505 4.9 13.5 0.009 B, D

GM06 02/02/22 N/A N/A N/A N/A N/A 0.039 B, D

Note 1. B: Bridge array records, D: Downhole array records

Pile Foundation Model

Material properties and FE model geometry

Medium clayG = 60 MPa, B = 300 MPa, Cohesion = 35.9 kPa, ρ = 1.5 t/m3

Stiff clay G = 150 MPa, B = 750 MPa,Cohesion = 76.6 kPa, ρ = 1.8 t/m3

Medium sandGr = 75 MPa, B = 200 MPa, = 33°,Pr = 80 kPa, ρ = 1.9 t/m3

Stiff clay G = 150 MPa, B = 750 MPa,Cohesion = 86.2 kPa, ρ = 1.8 t/m3

Medium sandGr = 75 MPa, B = 200 MPa, = 33°,Pr = 80 kPa, ρ = 1.9 t/m3

0 m-0.46 m-1.01 m

-2.13 m

-3.53 m

-5.49 m

-10.06 m

-12.50 m

-14.63 m

-16.77 m

Concrete pilecap Timber pilesE = 2480 MPa, v = 0.2 . E = 1240 MPa, v = 0.2

48 my

z

17 m

x

Embankment-Abutment Model

FE Model Geometry and Material Properties

Medium clayG = 60 MPa, B = 300 MPa, Cohesion = 35.9 kPa, ρ = 1.5 t/m3

Gravely clayG = 19 MPa, B = 90 MPa, Cohesion = 20 kPa, ρ = 1.6 t/m3

(Vs = 110 m/sec, v = 0.4)

Stiff clay G = 150 MPa, B = 750 MPa,Cohesion = 76.6 kPa, ρ = 1.8 t/m3

-18.0 m

-15.0 m

0.0 m

-7.5 m

7.9 m

-60 m 45 m0.0 m

Concrete abutment Timber pilesE = 2480 MPa, v = 0.2 . E = 1240 MPa, v = 0.2

x

z

Multi-Platform MRO Bridge Model

Note: Dimension of bridge is exaggerated.

x

yz

Mass defined in UI-SimCor

Structural modelin Zeus-NL

Geotechnical modelin OpenSees

System configuration

Multi-Platform MRO Bridge Model

0

10

20

30

Ch

ann

el

11

0

10

20

30

Ch

ann

el

3

0

10

20

30

Ch

ann

el

5

0

10

20

30

Ch

ann

el

7

0

10

20

30

Ch

ann

el

9

0

10

20

30

Ch

ann

el

13

0 0.1 0.2 0.3 0.4 0.50

10

20

30

Ch

ann

el

26

Period, sec T1 = 0.341 sec

GM01, T = 0.32

GM03, T = 0.34

GM04, T = 0.31

GM05, T = 0.33

GM06, T = 0.34

Analyt ical Model, T = 0.35

Ch 26 Ch 13 Ch 9 Ch 7 Ch 5 Ch 3 Ch 11

System identification from recorded ground motions and comparison with analytical model

MRO Bridge Analysis with SSI

Damping evaluation from GM03

-0.6

0.0

0.6

5 6 7 8 9 10 11 12 13 14 15

Time, sec

Dec

k re

lati

ve d

ispl

., cm

-0.05

0.00

0.05

5 6 7 8 9 10 11 12 13 14 15

Time, sec

Fre

e fi

eld

acce

lera

tion

, g

Maximum responseSubsequent peaks from near-free vibration

Impact-type earthquake loading

MRO Bridge Analysis with SSI

Time history analysis and comparison with recorded motion

-0.80

-0.60

-0.40

-0.20

0.00

0.20

0.40

0.60

0.80

0 1 2 3 4 5 6 7 8 9 10

Time, sec

Acc

, g

UI-SimCor

Measured - GM01

-0.30

-0.20

-0.10

0.00

0.10

0.20

0.30

3 4 5 6 7 8 9 10 11 12 13

Time, sec

Acc

, g

UI-SimCor

Recorded - GM03

-0.06

-0.04

-0.02

0.00

0.02

0.04

0.06

3 4 5 6 7 8 9 10 11 12 13

Time, sec

Acc

, g

UI-SimCor

Measured - GM04

-0.04

-0.02

0.00

0.02

0.04

2 3 4 5 6 7 8 9 10 11 12

Time, sec

Acc

, g

UI-SimCor

Measured - GM05

Summary

The MRO Bridge, which was heavily instrumented and studied, is modeled with two analysis platforms.

Each components of the soil-foundation-bridge system is verified through comparison with previous researches

Multi-Platform analysis is applied to combine two different platforms.

The modal properties is close to the properties identified from measured records.

The time history analysis result showed good correspondence with measured records.

Future Work

Future Work

FHWA No. 4 Bridge was selected as the prototype for experimental investigation– Using Zeus-NL with strong motion records, the effect

of vertical ground motion on bridge pier will be investigated

– 2~3 strong motion records will be selected from the analyses above

– Loading protocol from analyses will be provided to pier analysis with DIANA for more extensive analysis

Selection of Strong Motion Records and Loading Protocol

Future Work

The selected loading protocol will be verified using DIANA Using UI-SimCor, the computational simulation will be

conducted– Deck will be simulated using Zeus-NL– Piers will be analyzed using DIANA

The obtained result will be provided to experimental investigation

Verification by DIANA and Computational PSD simulation

Thank you &Questions?