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LimitState:GEO Eurocode 7

LimitState:GEO Eurocode 7. Colin Smith MA(Cantab) PhD Director & LimitState:GEO Product Manager , LimitState Ltd. 20/05/2008 LimitState:GEO launch & technology briefing - ICE London. 29/11/2014. geo1.0. Contents. Eurocode 7 Introduction LimitState:GEO functionality

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LimitState:GEO Eurocode 7

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  1. LimitState:GEOEurocode 7 Colin Smith MA(Cantab) PhD Director & LimitState:GEO Product Manager, LimitState Ltd 20/05/2008 LimitState:GEO launch & technology briefing - ICE London 29/11/2014 geo1.0

  2. Contents Eurocode 7 • Introduction • LimitState:GEO functionality • Examples

  3. Eurocode 7 Introduction geo1.0

  4. Eurocode 7 • Eurocode 7 has been under development since 1980. • Use of Eurocode 7 will be mandatory in the UK in 2010.

  5. Eurocode 7 Eurocode 7 moves away from: • working stresses, • overall factors of safety, to: • limit state design approach, • partial factors, • unified approach.

  6. Eurocode 7 It introduces a range of separate checks: • Ultimate Limit States (ULS) • Serviceability Limit States (SLS) EQU : loss of equilibrium STR : failure of the structure GEO : failure of the ground UPL : failure by uplift HYD : hydraulic heave 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  7. Eurocode 7 In the UK the checks against failure in the ground (GEO) and in the structure (STR) must be checked using ‘Design Approach 1’ which specifies 2 calculations : • Design combination 1 • Design combination 2 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  8. Loads Different factors are applied if loads are: • Permanent • Variable • Accidental Different factors are applied if loads are: • Favourable • Unfavourable i.e assist or resist collapse (this may not be clear at outset) 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  9. Partial Factors 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  10. Example – footing design Soil properties: cu = 70 kN/m2,  = 20 kN/m3 G D B • Geometry: • D= 0.75m, • B = 1 m 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  11. Example – footing design Soil properties: cu = 70,  = 20 kN/m3 G D B • Geometry: • D= 0.75m, • B = 1 m Gfail/B = 5.14 cu + D = 375 kN/m (unfactored) 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  12. Design Combination 1 Design Combination 1 Factors are primarily placed on the loads and the soil properties are unfactored. Factor on: Permanent load = 1.35 Variable load = 1.5 Usually controls failure in the structure 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  13. Design Combination 1 Factor on load = 1.35 G D B • Factor on cu • = 1.00 Gfail = 278 kN/m = (5.14 x 70 + 0.75 x 20) / 1.35 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  14. Design Combination 2 Design Combination 2 Factors are primarily placed on the soil properties and loads are unfactored. Factor on: c = 1.25 tan = 1.25 cu = 1.4 Usually controls failure in the ground. 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  15. Design Combination 2 Factor on load = 1.00 G D B Factor on cu = 1.4 Gfail = 272 kN/m = 5.14 x (70/1.4) + 0.75 x 20 c.f. Gfail = 278 kN/m for Combination 1 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  16. Partial Factors • Different factors are applied for different ULS cases • The purpose of the partial factors is to ensure the probability of failure is sufficiently low. 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  17. EC7 Challenges • Multiple ULS cases (e.g. GEO, STR, UPL) each with own set of partial factors • Use of multiple load types (Permanent, Variable, Accidental) • Favourable/unfavourable to be defined and… • Different failure modes to be checked (e.g. local/global, sliding/bearing etc) • Drained / undrained cases to be checked 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  18. LimitState:GEOfunctionality geo1.0

  19. Load type specification 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  20. Multiple scenarios • Choose to solve one or many scenarios in one go • Select partial factor sets • Set long term / short term (drained/undrained) solution mode 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  21. Scenario solutions 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  22. Examples 29/11/2014 geo1.0

  23. Analysis Analysis • At this stage, LimitState:GEO was used to analyse the problem as described in the previous slides (Hands on demo of software)

  24. Conclusions • LimitState:GEO has been designed to maximise ease of use with Eurocode 7: • Permanent, variable and accidental load specification • Unfavourable/favourable load specification • User can specify any partial factor set • Multiple scenarios can be solved together • The new unified approach in Eurocode 7 makes use of generic ULS analysis software such as LimitState:GEO directly applicable to all geotechnical problem types. • Flexible approach makes it easy to utilise partial factors from other design codes. 20/05/2008 LimitState:GEO launch & technology briefing - ICE London

  25. Thank you for listening geo1.0

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