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