Post on 03-Jan-2017
Oasys
Integral Bridge Analysis using Soil Structure Interaction
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Zeena
Farook
Geotechnical
Today’s Team
Oliver
Riches
Associate
Andrew
Anderson
Bridge
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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
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• In recent years have added marketing, sales, and development staff worldwide
Oasys Customers
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Structural software
Geotechnical software
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CAD software
Document Management software
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
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[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
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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
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• 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
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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
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• 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
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Rotation / Flexure Translation
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
K* equations
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22
K* equationsPD 6694-1
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
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Based on horizontal
displacement at H/2
(denoted, d′d )
22
Comparion of pure rotation with flexure Springman et al (1996)
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
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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)
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15
Soil structure interaction and research findings
Background- HA Integral Bridges Research
• Scoping study and workshop (2005)
•Desk study of integral bridge usage
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•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:
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PD 6694 compared to international guidance
• Limited International design guidance.
•No guidance for soil structure.
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•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
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Earlier research has demonstrated the relationship between soil and strain:
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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)
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• 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)
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Comparison of pure rotation with flexure
Springman et al (1996)
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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)
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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
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3. Soil stiffness parameters
4. Soil strains
Calibration of FREW against Laboratory Modelling
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Figure 13: Calibration of laboratory test results using soil structure interaction [Arup Stage 2 Report (2009)]
Analysis of Integral Bridges
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Incorporation of Numerical Model in FREW
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Integral Bridge Analysis Data
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FREW Output
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Frew Demonstration
Andrew Anderson
Bridge Engineer
Case Study Information/Background
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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
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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:oasys@arup.com
• Online training movies
• Telephone support at 0191 238 7559
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Any Questions?
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