A065 seismic design, response modification and retrofit of bridge

SEISMIC DESIGN, RESPONSE MODIFICATION, AND RETROFIT OF BRIDGES Kazuhiko Kawashima Department of Civil Engineering Tokyo Institute of Technology... The 1989 Loma Prieta, the 1994 Northr

SEISMIC DESIGN, RESPONSE

MODIFICATION, AND RETROFIT

OF BRIDGES

Kazuhiko Kawashima Department of Civil Engineering Tokyo Institute of Technology

PREFACE

This is a lecture note for “Seismic Design, Response Modification and Retrofit of

Bridges” at the Graduate Course of the Department of Civil Engineering, Tokyo

Institute of Technology, Japan The scientific and engineering knowledge on the

earthquake engineering is described in this note with an emphasis on the application to

bridges Since the contents includes a broad senses on the structural engineering, the

structural dynamics, the concrete engineering, the soil mechanics, foundation

engineering, the engineering seismology, and the construction engineering, students are

required to take those courses before studying this class

Bridges are unique structures in their structural responses compared to other

structures They are longitudinally lengthy There are various types of superstructures,

substructures, and foundations as shown in Figs P-1, P-2, P-3, and P-4 (Road

Maintenance Technology Center 1996), with complex geometries and dynamic response

characteristics However, bridges have a lower degree of static indeterminacy than

buildings Hence failure of a part of structural element such as columns or foundations

likely results in a collapse of the entire bridge system Effect of the soil-structure

interaction and the spatial variation of ground motions are significant in bridges than

buildings Since bridges are a vital component of transportation system, bridges should

have sufficient seismic safety in an earthquake

The 1989 Loma Prieta, the 1994 Northridge, the 1995 Kobe, the 1999 Taiwan and the

Turkey earthquakes caused significant damage to bridges and these events together with

the research triggered as a consequence of past earthquakes has led to significant

advances in seismic engineering of bridges

This lecture note shows the recent technologies for seismic design, seismic response

modification, and seismic retrofit of bridges Past seismic damage of bridges,

characterizations of ground motion, dynamic response analysis methods, seismic

response characteristics of bridges, and strength and ductility of reinforced concrete

columns are also described

Kazuhiko Kawashima Professor, Department of Civil Engineering

Tokyo Institute of Technology

Meguro, Tokyo, Japan e-mail: kawasima@cv.titech.ac.jp

Fig P-1 Types of Superstructure (1/2)

Fig P-1 Types of Superstructure (2/2)

Fig P-3 Types of Substructure (1/2)

Fig P-4 Types of Substructure (2/2)

Table of Contents

1 Engineering Characterization of Ground Motion

1.1 Ground Motions

1.2 Peak Ground Motions

1.3 Duration of Ground Accelerations

1.4 Response Spectra

1) Horizontal Component

2) Vertical Component

1.5 Acceleration Response Spectrum Taking Number of Response Cycle into Account

1.6 Force Reduction Factor Resulting from Nonlinear Response

1.7 Relative Displacement Response Spectrum

1.8 Residual Displacement Response Spectrum

1.9 Multiple Excitation Response Spectrum

2 Dynamic Response Analysis of Bridges

2.1 Introduction

2.2 Analytical Modeling of Bridges

1) Structural System

2) Stiffness Idealization

3) Mass Idealization

4) Damping Idealization

2.3 Dynamic Analysis for Seismic Response of Bridges

1) Equations of Motion

2) Linear Analysis Procedure

3) Single Mode Spectral Analysis

4) Nonlinear Analysis

5) Evaluation of Computed Solution

3 Seismic Damage in the Past Earthquakes

3.1 Loma Prieta and Northridge, USA, Earthquakes (Not yet included)

3.2 Pre-Kobe and Kobe, Japan, Earthquakes

1) Pre-Kobe Earthquakes

2) 1995 Kobe Earthquake

3.3 Kocaeli and Duzce, Turkey, Earthquakes

1) Kocaeli Earthquake

2) Duzce Earthquake

3.4 Chi Chi, Taiwan, Earthquake

4 Strength and Ductility of Reinforced Concrete Members

4.1 Strength and Ductility

4.2 Lateral Confinement of Concrete by Ties

1) Lateral Confinement Effect

a) Hysteresis for repeated full unloading and reloading

b) Hysteresis for partial unloading and full reloading

c) Hysteresis for full unloading and partial reloading

2) Lateral Confinement of Concrete by Carbon Fiber Sheets

a) Lateral confinement of concrete by CFS

b) Lateral confinement of concrete by both CFS and Ties

4.3 Loading Tests

1) Test Methods

2) Yield and Ultimate

3) Equivalent stiffness and energy dissipation

4.4 Effect of Various Factors on Strength and Ductility Capacities of Reinforced

Concrete Columns

1) Effect of Loading Hysteresis

2) Effect of Varying Axial Force

3) Effect of Bilateral Loading

4) Hybrid Loading Tests

5) Verification of Seismic Performance using Plot-size Models

4.5 Reinforced Concrete Columns with Enhanced Ductility

1) Interlocking Columns with Large Cross Sections

2) Unbonding of Longitudinal Bars at the Plastic Hinge

3) Prestressed concrete columns

4) Isolator built-in column

4.6 Seismic Performance of C-Bent Columns

5 Seismic Response of Bridges

5.1 Seismic Response Characteristics of Standard Bridges

5.2 Seismic Response Analysis of Kaihoku Bridge

5.3 Effect of Multiple Excitation

5.4 Effect of Pounding of Decks

1) Importance of Pounding

2) Idealization of Longitudinal Collisions of Two Elastic Bars using Impact Spring

3) Analysis of Seismic Response of a Straight Model Bridge with Pounding Effect

5.5 Seismic Response of a Curved Bridge with Poundings

1) Structural Response of Curved Bridges

2) Analytical Model of Expansion Joints

3) Analytical Prediction of Seismic Response

5.6 Seismic Response of Skewed Bridges

5.7 Seismic Response of Bridges Supported by Pile Foundations

5.8 Seismic Response of Bridges Supported by Spread Foundations

5.9 Response of Pile Foundations for Fault Dislocation

5.10 Seismic Response of Arch Bridges

5.11 Seismic Response of Cable Stayed Bridges

1) Dynamic Characteristics of Cable Stayed Bridges based on Forced Excitation

Tests

a) Onomichi Bridge

b) Suehiro Bridge

c) Yamato-gawa Bridge

d) MEiko-nishi Bridge

2) Natural Periods and Mode Shapes of Cable Stayed Bridges

3) Damping Ratios of Cable Stayed Bridges

4) Analysis of Damping Ratios of a Cable Stayed Bridges based on Measured

Records

a) Dynamic Characteristics of Suigo Bridge

b) Measured Records during Past Earthquakes

c) Dynamic Characteristics based on Measured Accelerations

d) Dynamic Response Analysis of Suigo Bridge

5) Damping Ratios Resulting fro Energy Dissipation at Movable Bearings

6) Dependence of Damping Ratios on Mode Shapes

a) Experimental Tests

b) Effect of Cable Types on the Damping Ratios in the Longitudinal Direction

c) Effect of Cable Types on the Damping Ratios in the Vertical Direction

d) Evaluation of Damping Ratios of Cable Stayed Bridges

e) Evaluation of Energy Dissipation Functions for the Model Bridges

f) Evaluation of Damping Ratio of Model Bridges Based on Energy Dissipation

Functions

7) Effect of Propagating Ground Motions for Cable Stayed Bridges

5.12 Seismic Performance of Long-span Bridges during the 1995 Kobe Earthquake

6 Seismic Design

6.1 Introduction

6.2 Practice of Seismic Design in Japan

1) Past History of Seismic Design

2) Seismic Performance Goals

3) Design Ground Motions

4) Design of Bridge System

5) Design of Reinforced Concrete Columns

a) Evaluation of Response Modification Factors

b) Evaluation of Strength and Ductility Capacity

c) Residual Displacement

d) Design Detailings

e) Comparison of Pre-Kobe and Post-Kobe Codes

6) Design of Foundations

7) Liquefaction and Liquefaction-Induced Ground Movement

6.3 Features of Recent Seismic Design Codes

1) Seismic Design Codes

2) Design Philosophy and Seismic Performance Criteria

3) Seismic Loads

4) Analytical Methods and Design Requirements

5) Response Modification Factors and Target Displacement Ductility Demand

7 Seismic Response Modification Design

7.1 Introduction

7.2 Seismic Response Modification using Viscous Damper Stoppers

7.3 Seismic Response Modification of Cable Stayed Bridges

7.4 Seismic Isolation

1) Principles

2) System Deign

3) Design of Devices

7.5 Implementation of Seismic Isolation

1) Application to 29-span Continuous Viaduct

a) Ohito Viaduct

b) DEsign

c) Detailings

2) Application of High Performance Stopper and Buffer Syste,

a) Wakayama Viaduct

b) Design

c) Cost Evaluation

3) Application to Reconstruction of a 19-span Continuous Viaduct

a) Benten Viaduct

b) Design

7.6 Technical Development for Seismic Isolation

1) Evaluation of Seismic Response Based on a Measured Acceleration

2) Development of Expansion Joints with Large Relative Displacement

3) Shock Absorbers for Mitigation of Pounding Effect

4) Effect of Pounding between Adjacent Decks

5) Isolator and Column Interaction

7.7 New Seismic Response Control Technology

1) Response Control by Variable Damper

2) Response Control of MR-Damper

8 Seismic Assessment and Retrofit

8.1 Introduction

8.2 Assessment of Seismic Vulnerability

8.3 Seismic Retrofit of Columns

1) Steel Jacket for Single Reinforced Concrete Columns

2) Reinforced Concrete Jacket for Wall Piers

3) Precast Concrete Jacket

4) Composite-Materials Jackets

5) Retrofit of Steel Columns

8.4 Seismic Retrofit of Foundations

1) Seismic Retrofit of Foundations with Inadequate Soil Bearing Caqpacity

2) Seismic Retrofit of Pile Foundations by Enlarging Footing and Increasing

Number of Piles

3) Seismic Retrofit of Reinforced Concrete Moment Resisting Piers

4) Seismic Retrofit of an 11-span Bridge Supported by Bent Piles in Liquefiable

Sandy Soils

5) Retrofit of Abutments using Expanded Polystyrene

9 Restoration Technology

9.1 Introduction

9.2 Principles of Restoration after the 1995 Kobe Earthquake

9.3 Restoration of Major Standard Bridges

1) 18-span Continuous Bridge, Fukae, Hanshin Expressway

2) Restoration using Seismic Isolation

3) Restoration of a Viaduct by Jacking-up of Decks

4) Restoration of Foundations against Lateral Spreading

9.4 Restoration of Long-Span Bridges

1) Akashi Straight Bridge

2) Restoration of Higashi Kobe Bridge

9.5 Advanced Technologies for Restoration

1) Damage Detection by Impact Loading Test

2) Damage Detection of Piles using Borehole Camera

3) Steel Jacketing for Reinforced Concrete Piers

4) New Composite Materials Jacketing and Precast Concrete Segment Jacketing

1 Engineering Characterization of Ground Motions

1.1 Ground Motions

Fig 1.1 shows accelerations measured at Sylmar Parking Lot in the 1994 Northridge, USA,

Earthquake and Kobe Observatory of Japan Meteorological Agency (JMA Kobe Observatory)

in the 1995 Kobe, Japan, Earthquake Displacements computed by integrating the

accelerations are also presented here The peak accelerations and velocities at Sylmar are 8.3

m/sec2, 0.32m and those at JMA Kobe Observatory are 8.2m/sec2 and 0.21m, respectively

They were recorded near the faults They include long period pulse accelerations The

durations are rather short; the durations with accelerations over 0.2g is 8 s and 5 s in the JMA

Kobe record and the Sylmar Parking Lot record, respectively They are typical examples of the

destructive ground motions that resulted in the significant damage in the Northridge and Kobe

Earthquakes

-10

-5

0

5

10

Acceleration

-10 -5 0 5 10

Acceleration

-0.3

0

0.3

Time (sec)

Displacement

-0.3 0 0.3

Time (sec)

Displacement

(a) Japan Meteorological Agency Kobe Observatory (b) Sylmar Parking Lot

Fig 1.1 Ground Motions in the 1994 Northridge, USA, Earthquake and the 1995 Kobe,

Japan, Earthquake

Ground motions are generated by a rupture of a fault Ground motion characteristics

depend on the location where they are recorded For example, Fig 1.2 shows the ground

accelerations recorded at JR-Takatori Station in the 1995 Kobe Earthquake JR-Takatori

Station was about 10 km apart from the JMA Kobe Observatory The intensity, the

predominant periods and the duration of the JR-Takatori Station record are very much

different with those of the JMA Kobe record

-5

0

5

10

2 )

Time (sec)

-10 -5 0 5 10

2 )

Time (sec)

Fig 1.2 Ground Acceleration at JR-Takatori Station the 1995 Kobe Earthquake

Ground motions recoded at the same location are not the same if they are generated by

different earthquakes For example, the ground accelerations presented in Fig 1.3 were

recoded at the ground surface in the vicinity of Kaihoku Bridge They were recorded in the

1978 Miyagi-ken-oki Earthquake (M=7.4) and a M6.7 event in 1978 Although they are

somewhat similar, they have different intensiiesy and periods This is because ground motions

depends on the source motions generated by a fault dislocation, the propagating path and the

amplification in the subsurface ground

-4

-2

0

2

4

(a) 1978 Miyagi-ken-oki Earthquake (M7.4)

-2

0

2

2 )

Time (sec)

(b) An Earthquake with Earthquake Magnitude of 6.7

Fig 1.3 Ground Motions at Nearby Ground of the Kaihoku Bridge

The recent earthquake-damage to bridges and other structures located within a few

kilometers from fault ruptures clearly indicates the importance to consider the near-field

ground motions Fig 1.4 shows typical near-field ground accelerations recoded at Sylmar

parking lot (NS-component) in the 1994 Northridge, USA, Earthquake, JMA Kobe

Observatory in the 1995 Kobe, Japan, Earthquake, Shikhkang (TCU068) in the 1999 Chi-Chi,

Taiwan, Earthquake, Bolu (L-component) and Duzce (L-component) in the Duzce, Turkey,

Earthquake The intensities of accelerations are very high, and they are characterized by

single pulses with large accelerations and long predominant periods Based on the response

acceleration spectrum, the JMA Kobe record has the highest response acceleration at natural

periods of 0.5-1 second It is noted that the Shikhkang record has the higher response

accelerations at natural periods over 2 s Such a record would develop extensive effect to

structures with long natural periods

As well as the strong intensity, the directivity of the near-field ground motion is important

in seismic design The pulses with large intensities are generally different in a direction

parallel or perpendicular to the fault plane, and depend on the amount and distribution of slip

developed on the fault rupture This is important when the bilateral directional excitation is

considered

-0.9

-0.6

-0.3

0

0.3

0.6

0.9

Max=0.84G NS

-0.9

-0.6

-0.3

0

0.3

0.6

0.9

Max=-0.83G NS

-0.6

-0.3

0

0.3

0.6

Max=0.51G EW

-0.9

-0.6

-0.3

0

0.3

0.6

0.9

Max=0.82G T

-0.6

-0.3

0

0.3

0.6

Duzce Max=-0.42G T

Time (s)