Foundations of High Rise Buildings

Transcription

1 Foundations of High Rise Buildings Prof. Dr.-Ing. Yasser El-Mossallamy Professor of Geotechnical Engineering Ain Shams Univ. Cairo, Egypt c/o Arcadis Consult, Germany Slide: 1 Development of High-rise Buildings in city centers Frankfurt New York Dubai Hongkong Slide: 2 prof. Dr. Ing. Yasser El-Mossallamy 1

2 prof. Dr. Ing. Yasser El-Mossallamy 2 Development of High-rise Buildings in city centers Although the cost of the foundation of a high rise building is only a small fraction of the total cost (about 10 to 15%), the foundation is one of the main design elements, which affects the whole behaviour of the building. On the other hand, the construction time of the foundation and basement floors takes about 30 to 50 % of the total construction time. These conditions make the foundation of high rise buildings one of the most critical construction items regarding the risk assessment analyses and optimization of construction schedule. Slide: 3 Different foundation types Piled foundation Piled raft 259 m 256 m Raft foundation 100 m Compressible soil Relatively incompressible soil Slide: 4

3 prof. Dr. Ing. Yasser El-Mossallamy 3 The Main Concept of Piled Raft a L = Q P / Q t Q t , Pk q sj P l a S 1.0 Piled raft foundation P k q sj L P l Traditional raft foundation Traditional pile foundation m D a L : Pile load share Q b a S = Settlement of piled raft Settlement of corresponding raft Slide: 5 Interaction aspects Q t Raft/soil (x,y) Raft/Piles X Y Z Q P,i,1 Q R aft = (x,y) da Q P,i,m D Pile/ Soil s a Piles/ Piles a s Pile/ Soil Z Q Raft Q = (x, y) i n Piles = Q p,i i 1 da n : No. of piles Slide: 6

4 prof. Dr. Ing. Yasser El-Mossallamy 4 Frankfurt as an example for development of foundations on compressible subsoil Slide: 7 Torhaus Messe Frankfurt b) load share c) Pile loads dependent on pile position Slide: 8

5 58.8 Messeturm, Frankfurt Totalstructuralload=1880MN G.W.T m b- Longitudinal section of the foundation Outer pile ring Middle pile ring Inner pile ring 58.8m c- Cross section of the tower above the foundation a) View d) Load share Slide: 9 Messeturm, Frankfurt e) Skin friction and pile forces dependent on depth Slide: 10 prof. Dr. Ing. Yasser El-Mossallamy 5

6 64.5 m 38.4 m prof. Dr. Ing. Yasser El-Mossallamy m How we measure: DG Bank, Frankfurt 208 m Settlement joint EXT / INK II Main tower Side building SDG 1 PWD P I SDG 12 SDG 13 P IV SDG 2 Quaternary 14,5 m 30 m Section Frankfurt clay EXT III SDG 3 PWD 2 P II P V SDG 7 P III SDG 8 PWD 4 SDG 10 SDG 9 SDG 11 PWD 5 P VI SDG 4 PWD 3 SDG 5 SDG m EXT / INK I 64.5 m Settlement joint N Inner core I I Plan 47.5 m Main tower Slide: 11 Instruments, Pile load cell Slide: 12

7 prof. Dr. Ing. Yasser El-Mossallamy 7 DG Bank, Frankfurt Measuring raft contact stresses Slide: 13 DG Bank, Frankfurt Measuring water pressure beneath the raft Slide: 14

8 prof. Dr. Ing. Yasser El-Mossallamy 8 DG Bank, Frankfurt Load-settlement behavior of piled raft, Load-time development a 0.6 L DG Bank Development of pile load share with time Time [days] Slide: 15 Instruments, Measuring room Slide: 16

9 Settlement [cm] Numerical analysis of piled raft Mathematical procedures Finite diference method (FDM) - One dimensional analysis (Load transfer method) - Two and three dimensional analysis Finite element method (FEM) - One dimensional analysis - Two dimensional analysis Plane strain Axisymmetry - Three dimensional analysis Boundary element method (BEM) - Using superposition technique - Complete boundary element structure Mixed technique - Hain and Lee (1978) - Hybrid model (O'Neill et al. 1981) - Modified hybrid model (Chow 1986) - El-Mossallamy (1996) Slide: 17 Comparison between observed and calculated behavior of piled raft L oad [MN] (a) (b) Observed behavior (b) E nd of construction Calculated, drained (a)1 year after end of construction a- Total load Calculated undrained Calculated, drained L oad [MN] Observed behavior L oad [MN] Calculated, drained Observed behavior b- Pile load share c- Raft load share Slide: 18 prof. Dr. Ing. Yasser El-Mossallamy 9

10 Depth (m) Settlement [cm] Different load settlement relationships Load [MN] (1) 4 (2) (4) (3) Legend (1) Single pile, (2) Average behaviorof the same pile as a member of an equally loaded free standinggroup, (3) Average behaviorof the same pile as a member of the pile group below the raft of the DG Bank (piled raft foundation) (4) The observedaverage behaviorof the piled raft piles. Domain of measured pile loads Slide: 19 Development of pile skin friction by piled raft Skin friction (kn/m²) Normal force (MN) (1) (2) (1) Calculated (2) Observed (1) (2) Slide: 20 prof. Dr. Ing. Yasser El-Mossallamy 10

11 Settlement [cm] Comparison between measured and calculated settlement Main Tower Side buildings I I Settlement joint Settlement joint Settlement trough along section I - I 1 Measurements, piled raft 2 Calculation, piled raft 3 Calculation, raft without piles Slide: 21 Main tower Side buildings Distribution of bending moments of the piled raft and of the corresponding raft without piles 1 2 Main tower Side buildings 1 2 Settlement joint Settlement jo Slide: 22 prof. Dr. Ing. Yasser El-Mossallamy 11

12 prof. Dr. Ing. Yasser El-Mossallamy 12 Contour lines of normalized vertical stresses beneath the center line of the piled raft and of the corresponding raft without piles Main Tower Side Building Main Tower Side Building Piled raft foundation Conventional raft foundation n n n = z o :Normalized vertical stresses z :Vertical stresses o :Average applied stresses of the main tower Settlement joint Slide: 23 Features of piled raft behavior: - Pile behavior depends on pile position - Pile capacity is completely difference than that of corresponding single pile - Skin friction develops from pile tip to pile top - Fewer number of piles can decrease the settlement significantly - Pile arrangement within pile group beneath the structural elements can reduce the raft internal stresses significantly. This has an effect on the reinforcement grad, on the raft thickness, on the required excavation depth, on the design of the required shoring system and on the required dewatering. Slide: 24

13 prof. Dr. Ing. Yasser El-Mossallamy 13 Application of piled raft in calcareous sand Foundation of High Rise Building (Kuwait) Salimia, El-Mossallamy et al. Slide: 25 Application of piled raft in calcareous sand Foundation of High Rise Building (Kuwait) Subsoil conditions Slide: 26

14 prof. Dr. Ing. Yasser El-Mossallamy 14 Application of piled raft in calcareous sand Foundation of High Rise Building (Kuwait) 624 piles with 0.9 m diameter 461 piles with 0.6 m diameter Pile length = 22 m Traditional deep foundation of the high-rise building Salimia, Kuwait Slide: 27 Behavior of calcareous sand Silica sand Calcareous sand Silica sand Calcareous sand Slide: 28

15 prof. Dr. Ing. Yasser El-Mossallamy 15 Application of piled raft in calcareous sand Foundation of High Rise Building (Kuwait) Results of pile load tests in Calcareous sand Slide: 29 Application of piled raft in calcareous sand Foundation of High Rise Building (Kuwait) 250 piles with 1.2 m diameter 146 piles with 0.6 m diameter Pile length = 17 m Proposal of an optimized piled raft for the high-rise building Salimia, Kuwait Slide: 30

16 prof. Dr. Ing. Yasser El-Mossallamy 16 Application of piled raft in calcareous sand Foundation of High Rise Building (Kuwait) Traditional deep foundation Piled raft foundation Total no. piles Pile diameter 0.9 and and 0.6 Pile length 22 m 17 m Total length of piles m 6732 m Comparison between traditional piled foundation and piled raft foundation Slide: 31 Application of piled raft in difficult geological conditions Foundation of High Rise Building (Jabal Omar Complex Makkah, Saudi Arabia) Slide: 32

17 prof. Dr. Ing. Yasser El-Mossallamy 17 Application of piled raft in difficult geological conditions Foundation of High Rise Building (Jabal Omar Complex Makkah, Saudi Arabia) Design aspects: 1- Foundation partially on soil, partially on rock 2- High earth pressure (30 m height) 3- Unequal earth pressure Slide: 33 Application of piled raft in difficult geological conditions Foundation of High Rise Building (Jabal Omar Complex Makkah, Saudi Arabia) Slide: 34

18 prof. Dr. Ing. Yasser El-Mossallamy m Plaxis 3D Foundation Case history: Japan Center m GW m a) Cross section 0.0 = 98.9 mnn Q T m m b) Plan Q = Quaternary Sand/Gravel T = Tertiary clay Slide: 35 Embedded piles Embedded piles: pile t skin F foot soil Slide: 36

19 prof. Dr. Ing. Yasser El-Mossallamy 19 3D FE-Model Slide: 37 Loads Slide: 38

20 prof. Dr. Ing. Yasser El-Mossallamy 20 Loads Slide: 39 Graphical presentation of the piles in different working planes Slide: 40

21 Deviatoric stress ( prof. Dr. Ing. Yasser El-Mossallamy 21 3D FE-Model Slide: 41 Applied Constitutive Law 1500 FEM results Test results CD - Triaxial test = 400 KN/m² = 200 KN/m² 300 = 100 KN/m² 3 ( q a q f 1 E 50 Asymptote 1 E ur Failure line Axial strain Axial strain 1 Hardening soil model g / g = 20 / 10 kn/m³ ref E = 30 MN/m² w = 1,0 50 ref c = 40 kn/m² f = 29 = 0,0 E ur = 90 MN/m² nref= 0.2 R f = 0.9 Slide: 42

22 Settlement (cm) prof. Dr. Ing. Yasser El-Mossallamy 22 Soil parameters Table 1: Geotechnical parameters a- Hardening soil mode Soil parameter Filling Quaternary Sand/Gravel E ref 50 [MN/m2 ] ref E ur [MN/m 2 ] Overconsolid ated clay ur [-] m [-] R f [-] / [kn/m 3 ] 18/8 19/11 20/10 k x [m/sec] x 10-5 k y [m/sec] k x c [kn/m 2 ] [ ] K o [-] where: E ref 50 Primary loading stiffness ref E ur Unloading/reloading stiffness ur Unloading/reloading Poisson s ratio m Power in stiffness laws R f Failure ratio / Total / Effective unit weight of soil c Cohesion Angle of internal friction K o Coefficient of earth pressure at rest k x, k y Permeability coefficient in the horizontal and vertical direction b- Mohr-Coulomb model Soil parameter Limestone E [MN/m 2 ] 750 [-] 0.3 / [kn/m 3 ] 20/10 k x [m/sec] 10-3 k y [m/sec] 10-3 c [kn/m 2 ] 200 [ ] 35 Structure elements Piles: E concrete = MN/m² and = 0.2 Anchor tendons: E steel = MN/m² Slide: 43 Foundation settlement under working loads obs. 1 Slide: 44

23 prof. Dr. Ing. Yasser El-Mossallamy 23 Piled raft of Minaret Slide: 45 Geological conditions (Rock surface contour lines Slide: 46

24 prof. Dr. Ing. Yasser El-Mossallamy 24 Geological Sections Slide: 47 Finite element model Igneous rock Alluvium deposit Alluvium deposit Slide: 48

25 prof. Dr. Ing. Yasser El-Mossallamy 25 Foundation model Igneous rock Slide: 49 Page 49 Piled raft of Minaret Igneous rock Slide: 50

26 prof. Dr. Ing. Yasser El-Mossallamy 26 Raft Settlement Max. settlement = 37.1 mm Slide: 51 Raft Settlement Max. settlement = 37.1 mm Slide: 52

27 prof. Dr. Ing. Yasser El-Mossallamy 27 Pile Stiffness (MN/m) Slide: 53 Page 53 Slide: 54

28 Embedded piles for large tanks on soft soil No. of piles = 376 Pile diameter = 1.5 m Tank cross section Slide: 55 Embedded piles for large tanks on soft soil Slide: 56 prof. Dr. Ing. Yasser El-Mossallamy 28

29 Embedded piles for large tanks on soft soil Slide: 57 Embedded piles for large tanks on soft soil INFOGRAPH Calculation - 3-dim. finite element analysis - Structural system modeled as an overall system - Dynamic analysis 0,600 a(t) 0,500 0,400 0,300 0,200 0,100 0, ,5 1 1,5 2 2,5 3 3,5 4 Slide: prof. Dr. Ing. Yasser El-Mossallamy 29

30 prof. Dr. Ing. Yasser El-Mossallamy 30 Embedded piles for large tanks on soft soil Slide: 59 Slide: 60

31 Structural engineers Geotechnical engineers Slide: 61 Design concept of piled rafts Lab testing (e.g. Triaxial tests) Field tests(e.g. SPT) Pile load test, Prototype Soil model Back-calculation Comparison Model Simulation soil-structure interaction Optimization analysis - economic conditions - serviceability requirements Foundation design Serviceability limit state Ultimate Limit state Determine the required structural parameter 1- pile stiffness depending on pile position 2- soil subgrade reaction modulus for the raft Structural design Slide: 62 prof. Dr. Ing. Yasser El-Mossallamy 31

32 J I H G F E High shelves 0.5 m D müm Neighboring building müm Neighboring building C Foundation = müm 17.0 m 14.0 m Neckar Street Tower Kaiser Street B A G.S. = müm GW cal.= müm prof. Dr. Ing. Yasser El-Mossallamy 32 Settlement (cm) Total applied load (MN) End of basic construction Final construction Time Conclusion / Résumé Foundation on overconsolidated clay Foundation on medium to dense sand Side building Gallusanlage Piled raft foundation Section 8-8 Foundation on soft clay Foundation on heterogeneous subsoil, uncoupled piled raft Raft Middle plastic clay Piles High plastic clay Moraine Compacted soil Application of piled raft Slide: 63 Conclusion / Résumé Controlling the settlement Optimizing the foundation design Piled raft foundation Increasing the bearing capacity F a) Prandtl zone for complete free flow failure pile existence neglected Aim of piled raft F g t t slip line neglected Slide: 64 b) Assumed block failure with free flow at the pile base area

33 prof. Dr. Ing. Yasser El-Mossallamy 33 Slide: 65