Dr. Deniz ULGEN, Dr. Selman SAGLAM, Dr. M. Yener OZKAN,

Dr. Jean. Louis CHAZELAS

Middle East Technical University, Mugla University, Adnan Menderes University, IFSTTAR

σT τ

σT

σN

σN

SEVENTH FRAMEWORK PROGRAMME

Capacities Specific Programme Research Infrastructures Project No.: 227887

Outline

� Introduction

�Summary of seismic design approaches of culverts

�Aim of the study

� Centrifuge test system

�Earthquake simulator, Model Container

�Soil properties, Preparation of model ground

�Design of culvert models

� Instrumentation

�Test program

� Results of Centrifuge Experiments

� Summary and Conclusions

Introduction-Summary of design methods

� Numerical analyses

- Computational effort, complex analysis

- Difficult to simulate the non-linear behavior of soil and soil

structure interaction

� Pseudo-static methods

� Force-based approach

-There is not generally accepted procedure

� Deformation based approach

� Free-field deformation method

� Soil-structure interaction approaches

- Simplified approaches Wang(1993), Penzien (2000), Bobet et

al. (2008)

Pseudo-static

Free-field deformation method

� Structure moves in accordance with soil

� Ignores the soil-structure interaction

� Overestimate or underestimate structure deformations depending on

relative stiffness between the soil and structure

∆structure=∆free-field

Soil Soil

∆free-field

Absence of culvert (free-field) Existence of culvert

Structure

Pseudo-static

Soil-structure interaction method

� Wang (1993)�Numerical solution

� Penzien (2000), Huo et al. (2006), Bobet et al. (2008) �Analytical solutions

R:Racking coefficient

F:Flexibillty Ratio

∆structure = R x ∆free-field

Structure

HS

LGF

s

1

=

Structure

11S1

H

L

F<1 structure is stiff relative to the free-field.

F>1 structure is flexible relative to the soil.

F=1 structure has same stiffness as the soil

∆structure

R=

∆free-field

R (Racking coeffcient)

F (Flexibility Ratio)

After Huo et al. (2006)

Pseudo-static

Soil-structure interaction method

Estimate the free-field deformation

Calculate flexibility ratio and find racking coefficient

Find structure’s deformation from ∆structure=R x ∆free-field

Compute sectional forces by imposing the deformation as a static load

Aim of the study

� Very few experimental data are currently avaliable

Motivation

� There is not generally accepted procedure to estimate dynamic

pressure acting on underground structures

σT τ

σT

σN

σN

Aim of the study

� To evaluate and understand dynamic pressures acting on the box-

type culverts

� To study the effects of flexibility ratio on dynamic response of

underground culverts

� To examine the deformation of culverts subjected to dynamic loading

Aim of the study

Centrifuge Test System

IFSTTAR Beam type centrifuge

Capacity:100g centrifugal acceleration 2tones model

Rotating arm (radius)=5.5m

Centrifuge Tests

Earth gravity

Centrifugal acceleration in Z direction

Z

Y

Shaking in Y direction

Centrifugal acceleration=40g

Centrifuge Test System

CHARACTERISTICS

Length of shaking table 1m

Width of shaking table 0.5m

Payload mass 400kg

Centrifugal acceleration20g to

80g

Maximum displacement 5mm

Maximum velocity 1m/s

Maximum acceleration 0.5g

Frequency range for

earthquake motions20-300Hz

Frequency range for

harmonic motions20-200Hz

Earthquake Simulator

Centrifuge Test System

Model Container (Equivalent Shear Beam Box)

Soil Properties

Physical Properties of Soil

Soil Fontainebleau Sand NE34

emin 0.55

emax 0.86

γγγγmin(kN/m3) 13.93 kN/m3

γγγγmax(kN/m3) 16.78 kN/m3

Mean diameter (D50) 0.20 mm

Specific gravity 2.64

Friction Angle 38°

Preparation of Model Ground

ID=70%

Relative Density =70%

CPT TESTS

to verify the uniformity and repeatability of the soil model prepared by pluviation

0

2

4

6

8

10

12

14

0 5000 10000 15000 20000

Depth (prototype scale) (m)Tip Resistance (kPa)

CPT-1

CPT-2

CPT-3

CPT-4

CPT-5

CPT-6

CPT-7

Design of Culvert Models

Thicker roof and invert slabs To eliminate structural effects due to bending

Culvert Model

Internal Dimensions

(mm)

External Dimensions

(mm)

Vertical Horizontal Vertical Horizontal

1 Thinnest Walls 38 44 50 47

2Intermediate

Thickness38 44 50 50

3 Thickest Walls 38 44 50 54

Model 1

(Thinnest Walls)

Model 2

(Intermediate Thickness)

Model 3

(Thickest Walls)

Teflon Sheet

Aluminium Sheet

Neoprene FoamCulvert top

slab

Culvert bottom

slab

Design of Culvert Models

ESB Box

Frames

Instrumentation

800

416

150

180

15 50

75 100

Laser Laser Laser

15 50

400

Z X

Y

Unit:mm:

Horizontal accelerometer // Y

Horizontal accelerometer //X

Shaking Direction

Instrumentation Vertical accelerometer

Horizontal accelerometer

A

A

B

B

InstrumentationDiagonal Extensometers

Horizontal Extensometers

Horizontal Extensometers

Diagonal Extensometer

Testing Program

Test # Culvert

Model #

Acc. Amp.

Sin Motion (g)

Prototype Scale

Frequency (Hz)

Prototype Scale

1 1 0.25 2

2 1 0.25 3.5

3 1 0.40 2

4 1 0.40 3.5

5 2 0.25 2

6 2 0.25 3.5

7 2 0.40 2

8 2 0.40 3.5

9 3 0.25 2

10 3 0.25 3.5

11 3 0.40 2

12 3 0.40 3.5

Centrifuge test results

Culvert

Left Sidewall

Culvert

∆ ∆

Centrifuge test results

Model 1

(Thinnest Walls)

0.25g -2Hz

Right Sidewall

∆str(Penzien)=6.7mm

∆str(Cent.)=3.4mm

Left Sidewall

Culvert

∆ ∆

Centrifuge test results

Model 2

(Intermediate

Thickness)

Right Sidewall

0.25g -2Hz

∆str(Penzien)=1.5mm

∆str(Cent.)=1.7mm

Left Sidewall

Culvert

∆ ∆

Centrifuge test results

Model 3

(Thickest Walls)

Right Sidewall

0.25g -2Hz

∆str(Penzien)=0.47mm

∆str(Cent.)=0.71mm

σT τ

σT

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σN

Pd=Kd.σv,mid

Pd

Kd Dynamic Coefficient

σv,mid Geostatic vertical stress

at mid-depth of culvert

Pd

Pd Peak value of triangular dynamic pressure distribution

Centrifuge test resultsSimplified Frame

Equivalent dynamic pressure distribution

FS=1.1

Summary and Conclusions

� Three different box-type culvert models having different rigidities..

� Fontaineblau dry sand → Ground model, RD=70%

� Input motion → Sinusoidal motions (Acc.→ 0.25g, 0.40g, Freq.→(2Hz, 3.5Hz)

� Culvert sidewall deformations →Culvert

Any Questions?