Post on 15-Sep-2014
An example of the use of Eurocodes in An example of the use of Eurocodes in the design of underground metro the design of underground metro
structuresstructures
Tony Gee and PartnersTony Gee and Partners
David BeadmanDavid Beadman
Presented byPresented by
British StandardsBritish Standards
••
EurocodesEurocodes
EurocodeEurocode 77Retaining wall designRetaining wall design
Temporary construction stages
Case C /DA1 Comb 2
Case B /DA1 Comb 1
1.01.351.0Effects of actions
Lesser of 0.5m or 1/10th of the depth below the last prop
0Over-dig allowance
1.251.01.0Partial factor on soil friction (tan �’)
1.61.01.0Partial factor on soil shear strength (cu/c’)
Ultimate loadcasesServiceability loadcase
Design parameters
Cases B and C Design Approach 1 Combinations 1 and 2
Temporary construction stages
Design Approach 1 Combinations 1 and 2
Cases B and C
Stage 1 Install retaining wall
Stage 2 Excavate and construct roof
Stage3 Excavate and construct waling beam
Stage 4 Excavate to formation level
Case C / Design Approach 1 Combination 2Case C / Design Approach 1 Combination 2
Stage 4 Excavate to formation level
Design only critical for final excavation stageDesign only critical for final excavation stage• Only necessary to
check the stability of each construction stage
• Actually analysed the full construction sequence
Case B / Design Approach 1 Combination 1Case B / Design Approach 1 Combination 1
Design critical at intermediate stagesDesign critical at intermediate stages
Stage 1 Install retaining wall
Stage 2 Excavate and construct roof
Stage3 Excavate and construct waling beam
Stage 4 Excavate to formation level
Serviceability Limit State (Serviceability Limit State (crackwidthcrackwidth limit)limit)
EurocodesEurocodes
• Principles (P) general statements and definitions – no alternatives
• Application Rules – examples of generally recognized rules that follow the Principles and satisfy their requirements
EurocodeEurocode 77Geotechnical Design Report (GDR)Geotechnical Design Report (GDR)
-1000
-500
0
500
1000
1500
2000
2500
3000
3500
4000
Time
Load
Kn
EurocodeEurocode 7 7 –– Observational MethodObservational Method
EurocodeEurocode 7 7 –– Observational MethodObservational Method(2)P The following requirements shall be
met before construction is started:• Establish limits of behaviour• Assess range of possible behaviour• Plan monitoring• Review monitoring• Plan contingency
EurocodeEurocode 7 7 –– Observational MethodObservational Method
Temporary Prop
EurocodeEurocode 22
Rules for Buildings
Piles require some special attention for buildability
EurocodeEurocode 22
Analysis programs unavailable
Spreadsheets written and checked
Comparison between BS5400 and the Comparison between BS5400 and the
Metro SpecificationMetro Specification
0.2mm0.25mmMaximum crack width
90mm75mmMinimum cover for structures cast against the ground
50mm35mmMinimum cover for durability for retaining wall members, as concrete cast in non-aggressive ground
fck=30N/mm2fcu=35N/mm2Concrete grade
100 years120 yearsDesign life
Metro Specification
BS5400Requirements
Retaining wall structureRetaining wall structure
Ground Conditions:
Made ground
Glacial till
Limestone
Retaining wallRetaining wallHard soft Secant piles
above the limestone.750mm dia. soft piles1180mm dia. hard piles at
1450mm c/c.
1060mm dia. Contiguous piles within the limestone with grout pipes between the piles.
EurocodeEurocode 22Crack width calculationCrack width calculation
Station crossStation cross--sectionsection• Structure hung from
roof
• Large fixed-end moments
EurocodeEurocode 22Lapping of barsLapping of bars
• Principle – not permitted to lap bars greater than 32mm diameter. (Not satisfied)
Equivalent perimeter of bundle = 40 x (2 + �) = 206mm
Number of bars in bundle:
(Assume 40mm diameter bars)
Two:
Equivalent diameter of a single bar = 56mm
Perimeter of equivalent bar = 56.6 x � = 178mm
EurocodeEurocode 22Equivalent diameter of bar bundlesEquivalent diameter of bar bundles
Equivalent perimeter of bundle = 40 x (3 + �) = 246mm
Number of bars in bundle:
(Assume 40mm diameter bars)
Three:
Equivalent diameter of a single bar = 69.3mm
Perimeter of equivalent bar = 69.3 x � = 218mm
EurocodeEurocode 22Equivalent diameter of bar bundlesEquivalent diameter of bar bundles
• Bundles of equivalent diameter greater than 55mm not permitted (Application Rule)
EurocodeEurocode 22Equivalent diameter of bar bundlesEquivalent diameter of bar bundles
• Bundles to be considered as notional bars for purposes of crack-width calculation (Application Rule)
Use of Use of EurocodesEurocodes
• Consistent design approach• Common design language between the
different nationalities• Enabled the use of the Observational
Method
Use of Use of EurocodesEurocodes
• Learning curve• Development of design tools• Use of EC7 checklists• Incomplete suite of new codes
Use of Use of EurocodesEurocodes