1. B VIGNESHWARAN ME-Structural Engineering SATHYABHAMA UNIVERSITY 1

2. DESIGN OF BORED CAST IN SITU LATERALLY LOADED PILE 2

3. GENERAL a.It is a type of deep foundation to transfer load to sub surface data, having adequate bearing capacity by friction or end bearing. b. If the results of site investigation show that the soil at shallow depth is unstable or if the estimated settlement is beyond acceptable limits, a pile foundation will be adopted. 3

4. Classification of piles function End bearingFrictiontensioncompressionAncho r material Concretewoodsheetcomposite Method of installation precastCast insituBored cast insitu Cased Un cased Driven cast insitu 4

5. FUNCTION OF PILE Transfer superstructure load Withstand lateral loads Uplift load Minimize settlement 5

6. LOADS ON THE PILE Structures supported on pile foundation are often subjected to lateral loads and moments in addition to vertical loads. The sources of lateral loads are traffic, seismic events, wind, waves, and earth pressure. Moments may arise due to the eccentricity of the vertical force, fixity of the superstructure to the foundation and the location of the resultant lateral force on the pile with reference to the ground surface. 6

7. STRUCTURAL CAPACITY Axial capacity where a pile is wholly embedded in the soil(having a undrained shear strength not less than 0.1 kgf/cm2) its axial carrying capacity is not limited by its strength as a long column Where piles are installed through very weak soils (having an undrained shear strength less than 0.1 kgf/cm2) special considerations shall be made to determine whether the shaft would behave as long column or not; Lateral load capacity Wind loadEarth quake loadMoving loadWater current changes 7

8. LOAD AND ITS COMBINATION: * Dead load * live load (crane load vehicle load) etc. *Wind load *EQ load 8 Serviceability 1.0 DL+1.0 IL 1.0 DL+0.8IL+0.8 WL 1.0 DL+0.8 WL Limit state of strength 1.5 DL+1.5 IL 1.2 DL+1.2IL+1.2 WL/EQ 1.5 DL+1.5 WL/EL

9. TYPES. 1. Long pile (L/d>30) 2. Short pile (L/d<20) In the case of short pile: the flexural stiffness EI of the material of the pile loses its significance. The pile behaves as a rigid member and rotates as a unit. 9

10. ASSUMPTION The laterally loaded pile behaves as an elastic member and the supporting soil behaves as an ideal elastic material. The theory of sub-grade reaction There is no axial load. 10

11. PILE BOUNDARY CONDITION boundary conditions are. 1. Fixed-headed pile. 2. Free-head pile. 3. Partially-restrained-head pile. 11

12. PILE BOUNDARY CONDITION cont.… In the case of fixed head piles, the pile is free to move only laterally but rotation is prevented completely, where as a pile with a partially restrained head moves and rotates under restraint. The partially restrained head is normally encountered in offshore drilling platforms and other similar structures. 12

13. RELATIVE STIFFNESS OF PILE T= (EI/nh) 1/5 Where E and I are the modulus of elasticity and the moment of inertia of the soil respectively. nh-is the unit modulus of the subgrade reaction. 13

14. DEPTH OF FIXITY 14

15. DEFLECTION CALCULATION: For a vertical pile length L, subjected to horizontal load Qg at the ground level and a moment Mg at the ground level, the solution for deflection y may be expressed as y = yA+ yB y= total deflection of the pile at any depth yA= deflection due to the horizontal load QR yB= deflection due to moment Mg at ground level 15

16. MOMENT CALCULATION Fixed end moment for fixed head piles MF=H(e+zf)/2 Fixed end moment for free head piles MF=H(e+zf)/2 H- lateral load in KN e- cantilever length above ground ZF- Depth of fixity 16

17. GENERAL REQUIREMENT Length of pile : length of pile above ground level+ length underground Dia of pile : min 300mm Concrete Grade: Minimum M25. (The minimum cement content shall be 400 kg/m3. However, with proper mix design and use of proper admixture the cement content may be reduced but in no case the cement content shall be less than 350 kg/m3. Bore may be terminated at a depth where the penetration with 1 tone chisel dropped from a height of 1.20m should not exceed 150mm for blows For piles subjected to uplift load, lateral load and moments, separately or with compressive loads, it would be necessary to provide reinforcement or the full depth of pile. 17

18. REINFORCEMENT: Longitudinal Reinforcement: Mini. Ast =0.4% of sectional area of pile. Main rod: Minimum 6Nos. bars shall be used. Minimum dia. of bar is 12mm. Lateral ties: Mini. Dia of links or spiral shall be 8 mm and spacing of links or spirals not less than 150mm. Clear cover main reinforcement in pile shaft shall be not less than 50 mm. Stiffener rings preferably of 16 mm diameter at every 1.5 m centre-to-centre 18

19. AREA OF STEEL AS PER SP 16 Find pu max/fck *d2 Pu max-factored force d-dia of pile Fck -characteristic compressive strength of concrete Mf/fck*d3 Mf-fixed end moment 19

20. Area of steel as per sp 16 … Find d/D’ From chart for the given reinforcement we can find as pt/fck Pt-percentage of steel 20

21. LATERAL REINFORCEMENT End of the pile for 3D Distance 0.6%of gross volume of pile Except 3D Distance 0.2% of gross volume of pile 21

22. CHECK FOR SHEAR Vu = factored shear at ultimate loads Shear stress =(Vu / bd) Table 61 from sp 16 for percentage of steel and fck we can find the allowable shear strength of concrete 22

23. DETAILING 23

24. CONFIRMATORY TEST ON PILE Pile load test is the most direct method for determining the safe loads on piles including its structural capacity with respect to soil in which it is installed. It is considered more reliable on account of its being in-situ test than the capacities computed by other methods 24

25. VERTICAL LOAD TEST The loading on the pile top equals twice the rated capacity or as specified in the case of a separate test pile and 1.5 times the rated capacity of the pile in case of a working pile. Loading shall be applied by the reaction method consisting of an hydraulic jack reacting centrally against a loaded platform. Supports of the platforms shall be adequately designed. Special anchor piles or any other suitable type of anchorage system may also be used. 25

26. VERTICAL LOAD TEST cont.. The load shall be applied to the pile top in increments of about one fifth the rated capacity of the pile or as specified. Settlement readings shall be taken before and after the application of cash new load increment and at 2, 4, 8,15,30,60 minutes and at every two hours until application of the next load increment. 26

27. Each stage of loading shall be maintained till the rate of movement of the pile top is not more than, 0.1 mm in first 30minutes, 0.2 mm per hours or until two hours have elapsed, whichever is later Unloading :shall be carried out in the same steps as loading. A minimum period of ½ hour shall be allowed to elapse between two successive stages of load decrement. The final rebound shall be recorded 6 hours after the entire test load has been removed. 27

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29. ACCEPTANCE The safe of the pile shall be the least of following values: i) 2/3 of final load at which the total displacement attains a value of 12mm. Unless otherwise required, in given case on the basis of nature and type structure in which case, the safe load should be corresponding to the stated total displacement permissible. ii) 50 percent of final load at which the total settlement equate the 10% of pile diameter in case of bored piles and 7.5 percent of bulb diameter in case of under – reamed piles. 29

30. LATERAL LOAD TEST The test shall be carried out in accordance with the provisions of IS: 2911– (part I) Loading shall be applied in increments of 20%. Each stage shall be maintained for a period till the rate of movement of the pile head is not more then 0.1 mm / 30 min. or 1 hr. whichever is greater. 30

31. LATERAL LOAD TEST cont.. Loading shall be continued till one of the following occurs: a) Deflection of the pile head exceeds 12 mm. b) The applied load on the pile is twice the assumed lateral load capacity of the pile in case of a separate test pile and 1 ⅓ Times the rates capacity in the cast of a working pile 31

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33. ACCEPTANCE The safe load shall be the smaller of the following: i) Half the final load for which the total deflection is 12 mm. ii) Loading corresponding to 5 mm total defection. NOTE: The deflection is at the cut off level of the pile. 33

34. THANK YOU 34