1. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 1 Overview of Structural Design and Detailing of Large Diameter Drilled Shafts (Caltrans Practice) Amir M. Malek, PE, PhD Senior Bridge Engineer (Technical Specialist) Office of Bridge Design Services California Department of Transportation

2. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 2 Outline Types of Large Diameter Shafts and Comparison Design Highlights and Review of LRFD Requirements Communications of Structural and Geotechnical Designers for LRFD of Shafts Highlights of Seismic Design and Detailing Requirements per Caltrans Seismic Design Criteria (SDC) Case Study

3. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 3 Applications and Types Used for high seismic loads also where small footprint is desirable Most effective where hard layer (rock) is reachable Used with/without casing Types I & II per SDC classification Type-I : More ductile performance, advantageous for short columns Type-II : Easier post-event repair, shaft enlargement of at least 18” (24” under study) to contain inelastic action to the column (SDC 7.7.3.5)

4. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 4 Test of 6’ diameter Type-I Shaft at UCLA

5. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 5 Test of 6’ diameter Type-I Shaft at UCLA

6. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 6 Types of Large Diameter Drilled Shafts (Caltrans SDC)

7. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 7 LRFD & Seismic Design Highlights Structural Designer provides Factored Loads for applicable Limit States Geotechnical Designer will provide tip elevations based on Compression, Tension, and Settlement also Factored Nominal Resistance for Service, Strength and Extreme Event Limit States (LRFD) Structural Designer performs Stability Analysis and provides tip elevation for Lateral Loads Structural Designer analyzes, designs and details the shaft for Seismic Demands according to Caltrans SDC Scour, Liquefaction and Lateral Spreading are considered in design (if applicable)

8. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 8 Review of LRFD Requirements Consider Service, Strength and Extreme Event Limit States for Geotechnical and Structural Design of the Shaft Follow MTD3-1 for Communications and Transfer of Information between SD and GS as summarized in the following Tables

9. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 9 Preliminary Design Data Sheet (to be provided by SD)

10. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 10 General Foundation Information (to be provided by SD)

11. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 11 Foundation Design Loads (to be provided by SD)

12. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 12 Lateral Stability (BDA Chapter 12) Available Software: LPILE, W-FRAME, or SAP

13. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 13 General Seismic Design Highlights (Requirements that may be affected by size/type of the shaft) Geometrical/Structural Irregularities Demand and Capacity P-Δ Effect Displacement Ductility Limitation Minimum Local Displacement Ductility Capacity

14. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 14 Geometrical/Structural Irregularities: Balanced Stiffness of Bents (SDC 7.1.1) Balanced Frame Geometry (SDC 7.1.2) Demand vs. Capacity (SDC 4.1.1) P-Δ Effect (SDC 4.2) Displacement Ductility Demand Limits (1.5-3/5 for bents supported by the shafts, per SDC 2.2.3) Minimum Local Displacement Ductility Capacity Limits (SDC 3.1.4.1)

15. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 15 Structural Analysis for Demand Assessment Use Expected Material Properties Determine Column/Shaft Plastic Moments from Section Analysis Use Mo=1.2Mp Use Push-over Analysis and Find Shear and Moment Demands at Collapse

16. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 16 Demand Calculation (Single Column Bent) Mo Vo Mo

17. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 17 Seismic Demand Calculation (Multi-Column Bent) Type-I Mo

18. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 18 Seismic Demand Calculation (Multi-Column Bent) Type-II Mo

19. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 19 Structural Design of the Shafts M ne Type II >= 1.25 M Demand (SDC 7.7.3.2) V n Type II >= V Demand (SDC 3.6.7) Shear capacity is calculated as a ductile member using SDC 3.6 requirements (for Type-II assume µ d =1)

20. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 20 Detailing Requirements No Splice Zones (SDC 8.1.1) Plastic hinge region and areas of M D >M y Ultimate Splices (SDC 8.1.2) Ductile members outside “No Splice Zone” Service Splice (MTD20-9) Capacity Protected Members like Bent Cap For Hoops and Spirals in Ductile Members Use Ultimate Splices, Except: No splices in spirals used in “No Splice Zones” (end anchorage has been used to improve constructability)

21. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 21 Case Study (Type-II) Top of the Pile Boundary Conditions: V & M (V=150 kips, M=3,750 k-ft)

22. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 22 Liquefied Layer

23. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 23

24. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 24

25. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 25

26. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 26

27. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 27 Case-I Results CompetentNot Liquefied Liquefied (I) Liquefied (II) Top Deflection (in.) 0.923.49.8 12.2 14.4 18.2 Mmax (kip-in.) (x10 -4 ) 5.36.57.6 9.2 9.4 11.5 Location of Mmax (ft) 71432 37 42 Vmax (kips)320268420 517 420 519 Location of Vmax (ft) 173250 55 57 Stable Length (ft) 34546575 Scour Included

28. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 28 Summary (Method-I)

29. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 29

30. ADSC/CALTRANS CIDH Pile Workshop Spring 2008 30 Thank You