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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. Outline.

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overview of structural design and detailing of large diameter drilled shafts caltrans practice

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

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

outline
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

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

applications and types
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)

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

slide4

Test of 6’ diameter Type-I Shaft at UCLA

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

slide5

Test of 6’ diameter Type-I Shaft at UCLA

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

types of large diameter drilled shafts caltrans sdc
Types of Large Diameter Drilled Shafts (Caltrans SDC)

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

lrfd seismic design highlights
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)

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

review of lrfd requirements
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

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

preliminary design data sheet to be provided by sd
Preliminary Design Data Sheet(to be provided by SD)

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

general foundation information to be provided by sd
General Foundation Information(to be provided by SD)

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

foundation design loads to be provided by sd
Foundation Design Loads(to be provided by SD)

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

lateral stability bda chapter 12 available software lpile w frame or sap
Lateral Stability (BDA Chapter 12) Available Software: LPILE, W-FRAME, or SAP

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

general seismic design highlights requirements that may be affected by size type of the shaft
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

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

slide14
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)

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

structural analysis for demand assessment
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

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

demand calculation single column bent

Mo

Vo

Demand Calculation (Single Column Bent)

Mo

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

seismic demand calculation multi column bent
Seismic Demand Calculation (Multi-Column Bent)

Mo

Type-I

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

seismic demand calculation multi column bent18
Seismic Demand Calculation (Multi-Column Bent)

Mo

Type-II

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

structural design of the shafts
Structural Design of the Shafts
  • MneTypeII >= 1.25 MDemand (SDC 7.7.3.2)
  • VnTypeII >= VDemand (SDC 3.6.7)
  • Shear capacity is calculated as a ductile member using SDC 3.6 requirements (for Type-II assume µd=1)

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

detailing requirements
Detailing Requirements
  • No Splice Zones (SDC 8.1.1)

Plastic hinge region and areas of MD>My

  • 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)

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

case study type ii
Case Study (Type-II)

Top of the Pile Boundary Conditions:

V & M (V=150 kips, M=3,750 k-ft)

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

slide22

Liquefied Layer

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

slide23

Typical

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

slide24

Typical

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

slide25

Typical

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

slide26

Typical

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

slide27

Scour Included

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

summary method i
Summary (Method-I)

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008

thank you
Thank You

ADSC/CALTRANS CIDH Pile Workshop

Spring 2008