22 - 23 November, 2010Institution of Civil Engineers

Bridge Design to Eurocodes - UK Implementation

22 - 23 November, 2010Institution of Civil Engineers

Developments in Integral Bridge DesignSteve Denton, Tim Christie - Parsons Brinckerhoff

Oliver Riches - Arup

Alex Kidd - Highways Agency

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

• Some important developments that:– enhance efficiency in design– provide greater flexibility to designers

Important developments 1. 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

– full height frame abutments on single row of piles– Embedded wall abutments

Important developments 2. Limit equilibrium equations for K*d

• Simplified to two equations for:– rotation and/or flexure: K*d = K0 + (C dd / H)0.6 Kp

– Translation: K*d = K0 + (40dd / H)0.4 Kp

Rotation / Flexure Translation

Important developments 2. Limit equilibrium equations for K*d

• Simplified to two equations for:– rotation and/or flexure: K*d = K0 + (C dd / H)0.6 Kp

– Translation: K*d = K0 + (40dd / H)0.4 Kp

22

K* equationsPD 6694-1

Important developments 2. Limit equilibrium equations for K*d

• Simplified to two equations for:– rotation and/or flexure: K*d = K0 + (C dd / H)0.6 Kp

– Translation: K*d = K0 + (40dd / H)0.4 Kp

Based on horizontal displacement at H/2 (denoted, dd )

Important developments 2. Limit equilibrium equations for K*d

• Simplified to two equations for:– rotation and/or flexure: K*d = K0 + (C dd / H)0.6 Kp

– Translation: K*d = K0 + (40dd / H)0.4 Kp

Based on horizontal displacement at H/2 (denoted, dd )

22

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

Important developments 2. Limit equilibrium equations for K*d

• Simplified to two equations for:– rotation and/or flexure: K*d = K0 + (C dd / H)0.6 Kp

– Translation: K*d = K0 + (40dd / H)0.4 Kp

Parameter, C, accounts of effect of ‘non-rigid boundary’ below foundation (i.e. the stiffness of ground below foundation).Varies between 20 and 66.

Important developments 2. Limit equilibrium equations for K*d

• Simplified to two equations for:– rotation and/or flexure: K*d = K0 + (C dd / H)0.6 Kp

– Translation: K*d = K0 + (40dd / H)0.4 Kp

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 developments 2. Limit equilibrium equation for K*d

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

Important developments 2. Limit equilibrium equation for K*d

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

15

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

Important developments 3. Combinations and partial factors

• Characteristic value of movement of end of deck given by:

dk = Lx (Te;max – Te;min )

• Design value is given by:

dd = 0.5dk (1 + Q )

• where, and Q are relevant values for thermal actions in the combination of actions under consideration

Important developments 3. Combinations and partial factors

• Horizontal earth pressure applied to bridge is equal to product of effective vertical stress and K*d , i.e.:

Horizontal earth pressure1 = zK*dG

• Where G is relevant partial factor for weight of soil

[1 note: assuming no pore water pressure]

Important developments 3. Combinations and partial factors

Important developments 3. Combinations and partial factors

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

18

The development of a numerical soils model

19

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

20

Earlier research has demonstrated the relationship between soil strain and:

Soil StiffnessSeed and Idriss (1970)

Mobilised Passive Resistance Terzaghi (1934), Hambly and Burland(1979)

21

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

• Increase in soil stiffness

• Increase in densification in loose soils and associated increase in max

• No effect on cohesive soils

22

Flexible abutments and soil strainsSpringman et al (1996)

23

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

24

Re-evaluation of values max triaxial = cv + 3 (Dr(10-ln’)-1) Bolton (1986) max triaxial = Initial max triaxial + ((0.9 – Dr)/0.1) Clayton et al (2007)

25

The effect of a rigid boundary at the hinge

Tapper and Lehane (2004) Tan and Lehane (2008)

26

K* equations PD 6694-1

27

Soil structure interaction using the numerical soils model

[31]

0.2500

[40]

0.2500

0.00 kN/m

0.00 kN/m

DisplacementsActive LimitPassive LimitActual eff. PressuresWater 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 1:293

-10.00

-5.000

.0

5.000

10.00

15.00

[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]

[41]

[42]

[42]

[43][44]

[44]

[44]

[45][45]

[45][45]

[46][46]

[46]

[47]

[47]

160.36 kN/m

577.72 kN/m

DisplacementsActive LimitPassive LimitActual eff. PressuresWater 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 1:276 y 1:293

-10.00

-5.000

.0

5.000

10.00

15.00

[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]

[41]

[42]

[42]

[43][44]

[44]

[44]

[45][45]

[45][45]

[46][46]

[46]

[47]

[47]

75.15 kN/m

108.22 kN/m

DisplacementsActive LimitPassive LimitActual eff. PressuresWater 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 1:276 y 1:293

-10.00

-5.000

.0

5.000

10.00

15.00

[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]

[41]

[42]

[42]

[43][44]

[44]

[44]

[45][45]

[45][45]

[46][46]

[46]

[47]

[47]

741.04 kN/m

3059.72 kN/m

DisplacementsActive LimitPassive LimitActual eff. PressuresWater 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 1:276 y 1:293

-10.00

-5.000

.0

5.000

10.00

15.00

[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

DisplacementsActive LimitPassive LimitActual eff. PressuresWater 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

28

Global Bridge Analysis

29

Examples of Soil Structure Interaction