Integral Bridge Analysis using Soil Structure Interaction

Oasys

Integral Bridge Analysis using Soil Structure Interaction

www.oasys-software.com

Zeena

Farook

Geotechnical

Today’s Team

Oliver

Riches

Associate

Andrew

Anderson

Bridge


Geotechnical

Application

Engineer

Associate

Bridge

Engineer

Bridge

Engineer

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Who is Oasys?

•Wholly owned by Arup

•Formed in 1976 to develop software for in-house and external use

•Most developers are engineers who have moved to programming

• In recent years have added marketing, sales, and


• In recent years have added marketing, sales, and development staff worldwide

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Structural software

Geotechnical software


CAD software

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Sustainability software

Webinar objectives

1. Appreciate the integration of Integral Bridge Analysis and SSI

2. Understand the development of the numerical model and input parameters

3. Understand the application of the model in Frew using case studies based on PD6694-1


[17]

7.500

[18][19][20][21][22][23][24][25][26][27][28][29][30][31]

[32]

0.2500

[33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]

95.38 kN/m

267.08 kN/m

Displacements

Active Limit

Passive Limit

Actual eff. Pressures

Water Pressure

-200.0 -100.0 .0 100.0 200.0

-40.00 -20.00 .0 20.00 40.00

Pressure [kN/m²]

Displacement [mm]

Scale x 1:270 y 1:284

-10.00

-5.000

.0

5.000

10.00

15.00

Integral Bridge Analysis and Developing the


Integral Bridge Analysis and Developing the Numerical Model

Oliver Riches

Associate

Introduction

• Section 9 and Annex A of PD 6694-1 cover Integral Bridges

•Based on BA42, but updated to:

• align with Eurocodes

• address known issues with BA42

• embrace latest research in the field


• embrace latest research in the field

• Some important developments that:

• enhance efficiency in design

• provide greater flexibility to designers

Background to development

For flexible abutments, soil pressure is a function of the displacement of the abutment which is a function of the soil stiffness.

Soil Structure Interaction Required

Abutment displacement Soil pressures Abutment Moments


Important developments1. Soil-structure interaction methods

•Both limit equilibrium and soil-structure interaction methods covered

• requirements for soil-structure interaction methods are given

in Section 9

• an approach is given in Annex A, alternatives may be used

• Soil-structure interaction methods are recommended for


• Soil-structure interaction methods are recommended for

• full height frame abutments on single row of piles

• embedded wall abutments

• piled bankseat abutments

Important developments2. Limit equilibrium equations for K*d

• Simplified to two equations for:

• rotation and/or flexure: K*d = K0 + (C d′d / H)0.6 Kp

• Translation: K*d = K0 + (40d′d / H)0.4 Kp


Rotation / Flexure Translation





K* equations


22

K* equationsPD 6694-1






Based on horizontal

displacement at H/2

(denoted, d′d )

22

Comparion of pure rotation with flexure Springman et al (1996)






Parameter, C, accounts of

effect of ‘non-rigid boundary’

below foundation (i.e. the

stiffness of ground below

foundation).

Varies between 20 and 66.

20

The effect of a rigid boundary at the hinge

Tapper and Lehane

(2004)

Tan and Lehane (2008)

Important developments2. Limit equilibrium equation for K*d

•For rotation and/or flexure earth pressure coefficient equal to K0 and depth, H

Soil response to repeated cycles of strainEngland et al (2000)


15

Soil structure interaction and research findings

Background- HA Integral Bridges Research

• Scoping study and workshop (2005)

•Desk study of integral bridge usage


•Review of existing data, back analysis of measured performance and recommendations:

• data collection and review

• geotechnical review / back analysis of laboratory tests

• final research report

The development of a numerical soils model:


PD 6694 compared to international guidance

• Limited International design guidance.

•No guidance for soil structure.


•Design for fully mobilised passive pressures or

•mobilised passive pressures.

Ministry of Transport, Ontario Design Guidance

Long term soil behaviour behind integral bridge abutments

Soil response to repeated cycles of strain

England et al 2000


Earlier research has demonstrated the relationship between soil and strain:


Soil Stiffness

Seed and Idriss 1970

Mobilised Passive Resistance

Terzaghi (1934)

Hambly and Burland (1979)

• Increase in soil stiffness

• Increase in densification in loose

Impact of repeated application of soil strains on soil stiffnessClayton et al (2007)


• Increase in densification in loose

soils and associated increase in

ϕ′max

• No effect on cohesive soils

Flexible abutments and soil strains

Springman et al (1996)


Comparison of pure rotation with flexure

Springman et al (1996)


Re-evaluation of ϕ′ϕ′ϕ′ϕ′ values

Relationship between ϕ′ϕ′ϕ′ϕ′max triaxial , ϕ′ϕ′ϕ′ϕ′max plane strain and ϕ′ϕ′ϕ′ϕ′ crit

Impact of densification

ϕ′ϕ′ϕ′ϕ′max triaxial = 0.6 ϕ′ϕ′ϕ′ϕ′max plane strain + 0.4 ϕ′ϕ′ϕ′ϕ′ crit Bolton (1986)


ϕ′ϕ′ϕ′ϕ′max triaxial = 0.6 ϕ′ϕ′ϕ′ϕ′max plane strain + 0.4 ϕ′ϕ′ϕ′ϕ′ crit Bolton (1986) ϕ′ϕ′ϕ′ϕ′ max triaxial = ϕ′ϕ′ϕ′ϕ′ cv + 3 (Dr(10-lnρρρρ’)-1) Bolton (1986)ϕ′ϕ′ϕ′ϕ′ max triaxial = Initial ϕ′ϕ′ϕ′ϕ′ max triaxial + ((0.9 – Dr)/0.1) Clayton et al

(2007)

Refer to PD 6694 for more information

Development of Numerical Model

Summary

1. Mobilised passive pressures

2. Effect of the rigid boundary


3. Soil stiffness parameters

4. Soil strains

Calibration of FREW against Laboratory Modelling


Figure 13: Calibration of laboratory test results using soil structure interaction [Arup Stage 2 Report (2009)]

Analysis of Integral Bridges


Incorporation of Numerical Model in FREW


Integral Bridge Analysis Data


FREW Output



Frew Demonstration

Andrew Anderson

Bridge Engineer

Case Study Information/Background


Summary

1. Integral Bridge Analysis and SSI

2. Development of the numerical model and input parameters

3. Case studies based on PD6694

⇒ Appreciate the motivations behind the development

⇒ Apply the feature to you design to save time and comply to standards


standards

[17]

7.500

[18][19][20][21][22][23][24][25][26][27][28][29][30][31]

[32]

0.2500

[33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]

95.38 kN/m

267.08 kN/m

Displacements

Active Limit

Passive Limit

Actual eff. Pressures

Water Pressure

-200.0 -100.0 .0 100.0 200.0

-40.00 -20.00 .0 20.00 40.00

Pressure [kN/m²]

Displacement [mm]

Scale x 1:270 y 1:284

-10.00

-5.000

.0

5.000

10.00

15.00

What next?

• Support:

• Web site and technical FAQs

• mailto:[email protected]

• Online training movies

• Telephone support at 0191 238 7559


Any Questions?


Integral Bridge Analysis using Soil Structure Interaction

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