Bridge Design to Eurocodes - Integral Bridge

22 - 23 November, 2010 Institution of Civil Engineers

Brid Br idge ge Design si gn to Euroc ur ocod ode es - UK Impleme Imp lement nta ation ti on

22 - 23 November, 2010 Institution of Civil Engineers

Dev el o p m en t s in i n In In t eg r al Bri Br i dge dg e Des i gn Steve Denton nt on,, Tim Christ Chri stie ie - Parson rs ons s Brin Br inckerho ckerhoff  ff  Oliver liver Riche Riches s - Arup  Al  A l ex K i d d - Hig Hi g h w ays ay s A g enc en c y

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 dd / H)0.6 Kp –  Translation: K*d =K0 +(40dd / 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 dd / H)0.6 Kp –  Translation: K*d =K0 +(40dd / H)0.4 Kp K* equations PD 6694-1

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Important developments 2. 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

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

Important developments 2. 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 Comparion of  pure rotation with flexure Springman et al (1996)

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

Important developments 2. 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 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 dd / H)0.6 Kp –  Translation: K*d =K0 +(40dd / H)0.4 Kp  The effect of a rigid boundary at the hinge  Tapper and Lehane (2004)  Tan and Lehane (2008)

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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.

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 Soil response to repeated cycles of strain England et al (2000)

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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*d G • 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

 The development of a numerical soils model

Soil response to repeated cycles of strain England et al (2000)

Earlier research has demonstrated the relationship between soil strain and:

Soil Stiffness Seed and Idriss (1970)

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

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

Flexible abutments and soil strains Springman et al (1996)

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

Re-evaluation of   values   max triaxial =  cv + 3 (Dr(10-ln’)-1)   max triaxial = Initial   max triaxial + ((0.9 – Dr)/0.1)

Bolton (1986) Clayton et al (2007)

 The effect of a rigid boundary at the hinge  Tapper and Lehane (2004)  Tan and Lehane (2008)

K* equations PD 6694-1

Displacement Displacement Displacement[mm] [mm] Displacement [mm]

Soil structure interaction using the numerical soils model

-40.00 -40.00 15.00 15.00

-20.00 -20.00

.0 .0 .0

20.00 20.00 20.00

40.00 40.00 40.00 40.00

267.08 kN/m 577.72 kN/m 0.00 kN/m 108.22 kN 3059.72 kN/m /m 10.00 10.00 10.00

5.000 5.000

.0

7.500 7.500

160.36 kN/m 95.38 kN/m 0.00 kN/m 75.15 kN/m 741.04

[17] [17] [18] [18] [19] [19] [20] [20] [21] [21] [22] [22] [23] [23] [24] [24] [25] [25] [26] [26] [26] [27] [27] [27] [28] [28] 0.2500 [28] [29] [29] [29] [30] [30] [30] [31] [31] [31] [31]

0.2500 0.2500 0.2500 0.2500 [32] [40] [32] [33] [33] [34] [34] [35] [35] [36] [36] [37] [37] [38] [38] [39] [39] [40] [40] [41] [41] [42] [42] [43] [43] [44] [44] [45] [45] [46] [46] [47] [47] [45] [45] [46] [46] [42] [42] [44] [44] [45] [45] [46] [46] [41] [41] [45] [45] [44] [44] [47] [47] [47]

-5.000

-10.00 -10.00 -10.00

Water Pressure Water Pressure Water WaterPressure Pressure Actual eff. Pressures Pressures Pressures Actual Actual eff. eff.Pressures Pressures PassiveLimit Limitt Passive Limit Passive Passive Limi Active Lim Active Limit ActiveLim Lim it itit Active Lim it Displacements Displacements Displacements Displacements

-200.0 -200.0 -200.0 -200.0 x1:270 1:276 yyy1:293 1:284 Scale 1:270 1:293 x 1:276 y1:293 Scale x x 1:276 y1:293

-100.0 -100.0 -100.0 -100.0

.0 .0 .0 .0 Pressure [kN/m²] Press ure[kN/m²] Pressure Pressure [kN/m²] Pressure

100.0 100.0 100.0 100.0 100.0

200.0 200.0 200.0 200.0 200.0

Global Bridge Analysis

Examples of Soil Structure Interaction