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June 13 - June 15, 2012REC 2012, Brno, Czech Republic1 Different models of soil-structure interaction and consequent reliability of foundation structure.

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Presentation on theme: "June 13 - June 15, 2012REC 2012, Brno, Czech Republic1 Different models of soil-structure interaction and consequent reliability of foundation structure."— Presentation transcript:

1 June 13 - June 15, 2012REC 2012, Brno, Czech Republic1 Different models of soil-structure interaction and consequent reliability of foundation structure Radim ČAJKA Technical University Ostrava, Faculty of Civil Engineering Czech Republic

2 June 13 - June 15, 2012REC 2012, Brno, Czech Republic2 Analyses of structures Reliability of the reinforced and pre-stressed concrete structure and foundation depends on a lot of factors, for example –strength and safety factors of materials (f ck,  c, f yk,  s ) –static and dynamic force loads (g, q, F g, F q,….) –deformation loads (  ,…  for example creep, shrinkage, temperature, subsoil deformation due to undermining or flooding Suitable soil – structure interaction model

3 June 13 - June 15, 2012REC 2012, Brno, Czech Republic3 Application on real structure

4 June 13 - June 15, 2012REC 2012, Brno, Czech Republic4 FEM analyses of reinforced space structure

5 June 13 - June 15, 2012REC 2012, Brno, Czech Republic5 Subsoil models used in FEM Principle condition for all subsoil models Settlement of subsoil (s) is equal to deformation of foundation (w) Space 3D FEM model Surface model Boussinesque halfspace Winkler Pasternak Modification and combination of these models

6 June 13 - June 15, 2012REC 2012, Brno, Czech Republic6 Settlement calculation model and active zone determination coefficient of structural strength - Czech Standard ČSN m = 0,1 to 0,5 - Eurocode EC 7 m = 0,2 (recommended value)

7 June 13 - June 15, 2012REC 2012, Brno, Czech Republic7 Analyses of subsoil settlement - Condition for active zone determination - Condition for subsoil settlement in each nodal point - Then contact stress and contact function in all nodal points

8 June 13 - June 15, 2012REC 2012, Brno, Czech Republic8 Active zone determination with respect to ČSN or EC Standard The depth of compressible subsoil layers (active zone) depends on size and shape of foundation, changes of subsoil compressibility and distribution of foundation elements The coefficient of structural strength varies in Czech Standard ČSN from m = 0,1 to m = 0,5 In accordance ČSN EN Design of geotechnical structures, the effective vertical stress from foundation contact pressure is equal to 20 % of effective geotechnical stress, i.s. practically for m=0,2

9 June 13 - June 15, 2012REC 2012, Brno, Czech Republic9 Explicit expression of stress under rectangular area

10 June 13 - June 15, 2012REC 2012, Brno, Czech Republic10

11 June 13 - June 15, 2012REC 2012, Brno, Czech Republic11 Analysis of stress in subsoil

12 June 13 - June 15, 2012REC 2012, Brno, Czech Republic12 Numerical integration Gauss quadrature formulae whereare weighting factor for interval, integration points of function f number of integration points Numerical integration of vertical stress

13 June 13 - June 15, 2012REC 2012, Brno, Czech Republic13 Shape functions of a 4-node element

14 June 13 - June 15, 2012REC 2012, Brno, Czech Republic14 Shape functions of a 8-node element - corner nodes - intermediate nodes

15 June 13 - June 15, 2012REC 2012, Brno, Czech Republic15 Jacobian of transformation

16 June 13 - June 15, 2012REC 2012, Brno, Czech Republic16 Contact stress course in element

17 June 13 - June 15, 2012REC 2012, Brno, Czech Republic17 Convergence to exact solution Division of loaded area into finite elements and degree of polynomial approximation (convergence of shape and size of loaded area), Accuracy of approximation of stress course in subsoil, i.e. number of Gauss integration points (convergence of subsoil).

18 June 13 - June 15, 2012REC 2012, Brno, Czech Republic18 Solved test examples Square area Triangle area Circle area The results are practically same for exact solution and numerical integration to 6 integration points

19 June 13 - June 15, 2012REC 2012, Brno, Czech Republic19 Application of designed solution Analysis of stress components under arbitrary area constructed from 4-noded and 8-noded isoparametric elements Analysis of settlement of non-linear elastic half-space modified with soil structural strength coefficient following EC and Czech standard Solution of soil – foundation and soil – structure interaction problems by means of FEM

20 June 13 - June 15, 2012REC 2012, Brno, Czech Republic20 Rigidity matrix of isoparametric plate element

21 June 13 - June 15, 2012REC 2012, Brno, Czech Republic21 Subsoil rigidity matrix Contact function Nodal contact parameter Matrix of contact function

22 June 13 - June 15, 2012REC 2012, Brno, Czech Republic22 Four - noded isoparametric semispace element

23 June 13 - June 15, 2012REC 2012, Brno, Czech Republic23 Test example of circular plate on elastic halfspace Shallow plate foundation -modulus of elasticity of concrete E c = 22, MPa -Poisson’s ratio  c  = 0,2 -plate thicknessh c = 0,1 m -radius of circular plate r = 1,0 m Subsoil -modulus of deformation, F5 E def = 5,0 MPa -Poisson’s ratio  p  = 0,4 -coefficient of structural strenght m = 0,2 -density of subsoil  = 19 kN.m -3 Load -uniformly distributed load p z = 100 kPa

24 June 13 - June 15, 2012REC 2012, Brno, Czech Republic24 Settlement s(x,y) of Halfspace under Circular Plate after 0 th and 10 th Iteration

25 June 13 - June 15, 2012REC 2012, Brno, Czech Republic25 Contact stress of Circular plate under Centre and Edge

26 June 13 - June 15, 2012REC 2012, Brno, Czech Republic26 Test comparison with TRIMAS published example Shallow plate foundation -modulus of elasticity of concrete E c = MPa -Poisson’s ratio  c  = 0,154 -plate thickness h c = 0,3 m -Dimensions of rectangular plate l x = 8,0 m, l y = 12,0 m Subsoil -modulus of deformation, F5 E def = 4361,5 kPa -Poisson’s ratio  p  = 0,38 -coefficient of structural strength m = 0,001 0,01 0,1… -density of subsoil  = 18,5 kN.m -3 Load -uniformly distributed line load p z = 68,6 kN.m -1

27 June 13 - June 15, 2012REC 2012, Brno, Czech Republic27 Example of Foundation Plate TRIMAS (RIB software) Foundation plate with rigid walls in cross section Solution of the 2D plate on 3D space soil elements (TRIMAS software) Solution with proposed surface subsoil model Active zone in subsoil in accordance ČSN and EC7

28 June 13 - June 15, 2012REC 2012, Brno, Czech Republic28 Bending moments and Contact Stresses

29 June 13 - June 15, 2012REC 2012, Brno, Czech Republic29

30 June 13 - June 15, 2012REC 2012, Brno, Czech Republic30 Design of Testing Equipment Structure

31 June 13 - June 15, 2012REC 2012, Brno, Czech Republic31 Soil – foundation interaction test

32 June 13 - June 15, 2012REC 2012, Brno, Czech Republic32 Conclusion Original and general method for stress solution in elastic halfspace was presented Presented subsoil model is suitable for soil – structure interaction task and can save 3D subsoil elements The mentioned solution eliminates difficulties encountered up until now, when trying to apply a soil CSN EN standard model in FEM interaction tasks. Comparison of various subsoil model shows great scattering results, sometimes more than 100 % Field soil – foundation interaction experimental tests are now performed Designed models will be verified and uncertainty eliminated

33 June 13 - June 15, 2012REC 2012, Brno, Czech Republic33 This paper was supported by the research project No. FR-TI2/746, program TIP, Ministry of Industry and Trade, Czech Republic Thank you for your attention


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