DEEP FOUNDATION TYPES DESIGN AND CONSTRUCTION ISSUES

Transcription

1 DEEP FOUNDATION TYPES DESIGN AND CONSTRUCTION ISSUES OFFICE OF STRUCTURAL ENGINEERING OHIO DEPARTMENT OF TRANSPORTATION JAWDAT SIDDIQI P.E. ASSISTANT ADMINISTRATOR

2 Reliability Index #&! #&!!" # $%!" # $% The LRFD philosophy provides a more uniform, systematic, and rational approach to the selection of load factors and resistance factors than LFD.

3 LRFD: Load & Resistance Factor Design For Safety: η γ Q φ R = R i i i n r Q i - Load Effect R n - Component Resistance γ i - Load Factor φ - Resistance Factor i - Load Modifier (Ductility, Redundancy and Operational Importance) R n - Factored Resistance

4 Variability of Loads and Resistances '()&*%+(

5 Variability of Loads and Resistances σ = σ + σ 2 2 ( R Q) R Q β = Mean R Q σ ( ) ( R Q)

6 Reliability Index β P(Failure) % % % % %

7 Reliability Index AISC: β D+(L or S) D+L+W D+L+E Members Connections AASHTO: β = 3.5 Super/Sub Structures β = 2.3 Foundations

8 LRFD: Load & Resistance Factor Design For Safety: η γ Q φ R = R i i i n r Q i - Load Effect R n - Component Resistance γ i - Load Factor φ - Resistance Factor i - Load Modifier (Ductility, Redundancy and Operational Importance) R n - Factored Resistance

9 LRFD: Load & Resistance Factor Design Table Load Combinations and Load Factors. Load Combination Limit State DC DD DW EH EV ES EL LL IM CE BR PL LS WA WS WL FR TU CR SH TG SE Use One of These at a Time EQ IC CT CV STRENGTH I (unless noted) p /1.20 TG SE STRENGTH II p /1.20 TG SE STRENGTH III p /1.20 TG SE STRENGTH IV p /1.20 STRENGTH V p /1.20 TG SE EXTREME EVENT I EXTREME EVENT II p EQ p SERVICE I /1.20 TG SE SERVICE II /1.20 SERVICE III /1.20 TG SE SERVICE IV / FATIGUE LL, IM & CE ONLY 0.75

10 LRFD: Load & Resistance Factor Design Table Load Combinations and Load Factors. DC DD LL Use One of These at DW IM a Time EH CE Load Combination Limit State EV ES EL BR PL LS WA WS WL FR TU CR SH TG SE EQ IC CT CV STRENGTH I (unless noted) STRENGTH II STRENGTH III STRENGTH IV STRENGTH V p /1.2 TG SE p /1.2 TG SE p /1.2 TG SE p /1.2 p /1.2 TG SE

11 LRFD: Load & Resistance Factor Design Table Load Combinations and Load Factors. Load Combinatio n Limit State EXTREME EVENT I EXTREME EVENT II FATIGUE LL, IM & CE ONLY DC DD DW EH EV ES EL LL IM CE BR PL LS WA WS WL FR Use One of These at a Time TU CR SH TG SE EQ IC CT CV p EQ p

12 LRFD: Load & Resistance Factor Design Table Load Combinations and Load Factors. Load Combinati on Limit State SERVICE I SERVICE II SERVICE III SERVICE IV DC DD DW EH EV ES EL LL IM CE BR PL LS WA WS W L FR TU CR SH TG SE E Q Use One of These at a Time /1.20 TG SE / /1.20 TG SE / I C C T C V

13 Resistance Factors Table Resistance Factors for Geotechnical Resistance of Shallow Foundations at the Strength Limit State. Method/Soil/Condition Resistance Factor Theoretical method (Munfakh et al., 2001), in clay 0.50 Theoretical method (Munfakh et al., 2001), in sand, using CPT 0.50 Bearing Resistance ϕ b Theoretical method (Munfakh et al., 2001), in sand, using SPT 0.45 Semi-empirical methods (Meyerhof, 1957), all soils 0.45 Footings on rock 0.45 Plate Load Test 0.55 Precast concrete placed on sand 0.90 Sliding ϕ τ Cast-in-Place Concrete on sand 0.80 Cast-in-Place or precast Concrete on Clay 0.85 Soil on soil 0.90 ϕ ep Passive earth pressure component of sliding resistance 0.50

14 Resistance Factors Table Resistance Factors for Driven Piles. Condition/Resistance Determination Method Driving criteria established by static load test(s); quality control by dynamic testing and/or calibrated wave equation, or minimum driving resistance combined with minimum delivered hammer energy from the load test(s). For the last case, the hammer used for the test pile(s) shall be used for the production piles. Resistance Factor Values in Table 2 Nominal Resistance of Single Pile in Axial Compression Dynamic Analysis and Static Load Test Methods, ϕ dyn Driving criteria established by dynamic test with signal matching at beginning of redrive conditions only of at least one production pile per pier, but no less than the number of tests per site provided in Table 3. Quality control of remaining piles by calibrated wave equation and/or dynamic testing. Wave equation analysis, without pile dynamic measurements or load test, at end of drive conditions only FHWA-modified Gates dynamic pile formula (End of Drive condition only) Engineering News Record (as defined in Article ) dynamic pile formula (End of Drive condition only)

15 Resistance Factors Table Resistance Factors for Driven Piles (continued). Nominal Resistance of Single Pile in Axial Compression Static Analysis Methods, ϕ stat Condition/Resistance Determination Method Skin Friction and End Bearing: Clay and Mixed Soils α-method (Tomlinson, 1987; Skempton, 1951) β-method (Esrig & Kirby, 1979; Skempton, 1951) λ-method (Vijayvergiya & Focht, 1972; Skempton, 1951) Skin Friction and End Bearing: Sand Nordlund/Thurman Method (Hannigan et al., 2005) SPT-method (Meyerhof) CPT-method (Schmertmann) End bearing in rock (Canadian Geotech. Society, 1985) Resistance Factor Block Failure, ϕ b1 Clay 0.60 Uplift Resistance of Single Piles, ϕ up Nordlund Method α-method β-method λ-method SPT-method CPT-method Load test Group Uplift Resistance, ϕ ug Sand and clay 0.50 Horizontal Geotechnical Resistance of Single Pile or Pile Group Structural Limit State Pile Drivability Analysis, ϕ da All soils and rock 1.0 Steel piles See the provisions of Article Concrete piles See the provisions of Article Timber piles See the provisions of Article and Steel piles See the provisions of Article Concrete piles See the provisions of Article Timber piles See the provisions of Article In all three Articles identified above, use ϕ identified as resistance during pile driving

16 Resistance Factors Table Resistance Factors for Driven Piles (continued). Nominal Resistance of Single Pile in Axial Compression Static Analysis Methods, ϕ stat Condition/Resistance Determination Method Skin Friction and End Bearing: Clay and Mixed Soils α-method (Tomlinson, 1987; Skempton, 1951) β-method (Esrig & Kirby, 1979; Skempton, 1951) λ-method (Vijayvergiya & Focht, 1972; Skempton, 1951) Skin Friction and End Bearing: Sand Nordlund/Thurman Method (Hannigan et al., 2005) SPT-method (Meyerhof) CPT-method (Schmertmann) End bearing in rock (Canadian Geotech. Society, 1985) Resistance Factor

17 Resistance Factors ϕ dyn x R n = ϕ stat x R nstat (C ) where: ϕ dyn = the resistance factor for the dynamic method used to verify pile bearing resistance during driving specified in Table R n = the nominal pile bearing resistance (kips) ϕ stat = the resistance factor for the static analysis method used to estimate the pile penetration depth required to achieve the desired bearing resistance specified in Table R nstat = the predicted nominal resistance from the static analysis method used to estimate the penetration depth required (kips)

18 Resistance Factors The Ultimate Bearing Value for each pile to be shown in the plans shall be determined as follows: R ndr i i = η γ φ DYN Q i Where: Rndr = Ultimate Bearing Value (Kips) ηiγ iq i = Total factored load for highest loaded pile at each substructure unit (Kips) DYN = Resistance factor for driven piles DYN = 0.70 for piles installed according to CMS 507 and CMS 523.

19 Resistance Factors Table Resistance Factors for Driven Piles (continued). Condition/Resistance Determination Method Resistance Factor Block Failure, ϕ b1 Clay 0.60 Uplift Resistance of Single Piles, ϕ up Nordlund Method α-method β-method λ-method SPT-method CPT-method Load test Group Uplift Sand and clay 0.50 Resistance, ϕ ug

20 Resistance Factors Table Resistance Factors for Driven Piles (continued). Structural Limit State Condition/Resistance Determination Method Resistance Factor Steel piles See the provisions of Article Concrete piles See the provisions of Article Timber piles See the provisions of Article and Pile Drivability Analysis, ϕ da Steel piles See the provisions of Article Concrete piles See the provisions of Article Timber piles See the provisions of Article In all three Articles identified above, use ϕ identified as resistance during pile driving

21 Resistance Factors Resistance Factors For axial resistance of piles in compression and subject to damage due to severe driving conditions where use of a pile tip is necessary: H-piles φ c = 0.50 pipe piles φ c = 0.60 For axial resistance of piles in compression under good driving conditions where use of a pile tip is not necessary: H-piles φ c = 0.60 pipe piles φ c = 0.70 For combined axial and flexural resistance of undamaged piles: axial resistance for H-piles φ c = 0.70 axial resistance for pipe piles φ c = 0.80 Flexural resistance φ f = 1.00

22 Resistance Factors Table Relationship between Number of Static Load Tests Conducted per Site and ϕ (after Paikowsky et al., 2004). Number of Static Load Tests per Site Resistance Factor, ϕ Site Variability a Low a Medium a High a >

23 Resistance Factors Table Number of Dynamic Tests with Signal Matching Analysis per Site to Be Conducted During Production Pile Driving (after Paikowsky et al., 2004). Site Variability a Low a Medium a High a Number of Piles Located Within Site Number of Piles with Dynamic Tests and Signal Matching Analysis Required (BOR) < >

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32 Resistance Factors Table Resistance Factors for Geotechnical Resistance of Drilled Shafts. Method/Soil/Condition Resistance Factor Side resistance in clay α-method (O Neill and Reese, 1999) 0.45 Tip resistance in clay Total Stress (O Neill and Reese, 1999) 0.40 Side resistance in sand β-method O Neill and Reese, 1999) 0.55 Tip resistance in sand O Neill and Reese (1999) 0.50 Nominal Axial Compressive Resistance of Single-Drilled Shafts, ϕ stat Side resistance in IGMs O Neill and Reese (1999) 0.60 Tip resistance in IGMs O Neill and Reese (1999) 0.55 Side resistance in rock Horvath and Kenney (1979) O Neill and Reese (1999) 0.55 Side resistance in rock Carter and Kulhawy (1988) 0.50 Tip resistance in rock Canadian Geotechnical Society (1985) Pressuremeter Method (Canadian Geotechnical Society, 1985) O Neill and Reese (1999) 0.50 Block Failure, ϕ b1 Clay 0.55 Uplift Resistance of Single-Drilled Shafts, ϕ up Clay α-method (O Neill and Reese, 1999) 0.35 Sand β-method (O Neill and Reese, 1999) 0.45 Rock Horvath and Kenney (1979) Carter and Kulhawy (1988) 0.40 Group Uplift Resistance, ϕ ug Sand and clay 0.45 Horizontal Geotechnical Resistance of Single Shaft or Shaft Group All materials 1.0 Static Load Test (compression), ϕ load All Materials Values in Table , but no greater than 0.70 Static Load Test (uplift), ϕ upload All Materials 0.60

33 Resistance Factors Table Resistance Factors for Geotechnical Resistance of Drilled Shafts. Method/Soil/Condition Resistance Factor Side resistance in clay α-method (O Neill and Reese, 1999) 0.45 Tip resistance in clay Total Stress (O Neill and Reese, 1999) 0.40 Nominal Axial Compressive Resistance of Single- Drilled Shafts, ϕ stat Side resistance in sand β-method O Neill and Reese, 1999) 0.55 Tip resistance in sand O Neill and Reese (1999) 0.50 Side resistance in IGMs O Neill and Reese (1999) 0.60 Tip resistance in IGMs O Neill and Reese (1999) 0.55 Side resistance in rock Horvath and Kenney (1979) O Neill and Reese (1999) 0.55 Side resistance in rock Carter and Kulhawy (1988) 0.50 Tip resistance in rock Canadian Geotechnical Society (1985) Pressuremeter Method (Canadian Geotechnical Society, 1985) O Neill and Reese (1999) 0.50 Block Clay 0.55 Failure, ϕ b1

34 Resistance Factors Table Resistance Factors for Geotechnical Resistance of Drilled Shafts. Uplift Resistance of Single-Drilled Shafts, ϕ up Group Uplift Resistance, ϕ ug Method/Soil/Condition Clay Sand α-method (O Neill and Reese, 1999) β-method (O Neill and Reese, 1999) Rock Horvath and Kenney (1979) Carter and Kulhawy (1988) Sand and clay Resistance Factor

35 Resistance Factors Table Resistance Factors for Geotechnical Resistance of Drilled Shafts. Horizontal Geotechnical Resistance of Single Shaft or Shaft Group Static Load Test (compression), ϕ load Method/Soil/Condition Resistance Factor All materials 1.0 All Materials Values in Table , but no greater than 0.70 Static Load Test (uplift), ϕ upload All Materials 0.60

36 Intermediate Geo Materials Intermediate Geo Materials (IGMs) For detailed settlement estimation of shafts in IGMs, the procedures provided by O Neill and Reese (1999) should be used. C IGMs are defined by O Neill and Reese (1999) as follows: Cohesive IGM clay shales or mudstones with an S u of 5 to 50 ksf, and Cohesionless granular tills or granular residual soils with N1 60 greater than 50 blows/ft.

37 Intermediate Geo Material (IGM) b Side Resistance q = σ 4.0 for ( b-1) s in which, for sandy soils: for N 60 15: v β = z ( b-2) for N 60 < 15: N 60 β = ( z ) ( b-3) 15 in which, for IGM s: for N 60 50: β = ( z) 0.75 ( b-4)

38 Intermediate Geo Material (IGM) c Tip Resistance for sandy soils: for N 60 < 50: q p = 1.2 N 60 ( c-1) for IGM s: for N 60 50: p 0.8 a q p = 0.59N 60 σv σ ' v ( c-2)

39 Scour Assessment of Rocks Bridges on aggressive steams and waterways

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52 Thank You