The National Academies Press

Currently Skimming:

Pages 33-70

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.

From page 33... ... 3.1.2 Driven Piles -- Dynamic Analysis 3.1.2.1 The Analyzed Cases Time of driving, driving resistance, and area ratio proved to be controlling parameters for the dynamic methods (section 2.5.3) Read the entire page →
From page 34... ... , See Tables 7a and 8 for soil properties' correlations to SPT and CPT respectively, 36 = limiting friction angle, B = pile diameter 2B, 11.5B contributing zone to tip resistance. TABLE 16 The performance of the driven piles' static analysis methods -- statistical summary and resistance factors for data using mean ± 2 SD Read the entire page →
From page 35... ... The resistance factors for the different target reliability values were calculated for a ratio of dead load to live load of 2.0. Reviewing the information 0 0.5 1 1.5 2 2.5 3 KSX = Ratio of Static Load Test Results over the Pile Capacity Prediction using the α-API method 0 1 2 3 4 5 6 7 8 9 10 N um be r of Pi leC a se s 0 0.025 0.05 0.075 0.1 0.125 0.15 0.175 R ela tiv e Fr eq ue n cy log-normal distribution mlnx = -0.270 σlnx = 0.428 normal distribution mx = 0.832 σx = 0.349 Figure 17. Read the entire page →
From page 36... ... This is done by checking the number of case histories needed to be eliminated when limiting the set being investigated to those within the two standard deviation band, recalculating the resistance factors for the recommended target reliabilities, evaluating equivalent factors of safety, and examining the efficiency of the Figure 18. Histogram and frequency distributions of Ksx for 36 cases of concrete and pipe pile types in clay. Read the entire page →
From page 37... ... can be directly compared to the current specifications and other LRFD codes based on FOSM. 3.2.3 Equivalent Factors of Safety The fact that the resistance factors using FORM approximate those obtained by FOSM allows the use of a simplified relationship between resistance factor and FS based on FOSM and provided by Barker et al., 1991: (32) Read the entire page →
From page 38... ... 3.2.4 Detailed Tables Tables 19, 20, and 21 present detailed evaluations of the analyzed case histories for static analyses of driven piles, dynamic analyses of driven piles, and static analyses of drilled shafts, respectively. The tables include the number of case histories in the subset as well as the number of case histories used in the analysis of resistance factors. Read the entire page →
From page 39... ... The recommended resistance factors based on Tables 18 through 22 are presented in section 3.4. 3.2.5 Resistance Factors for Pullout of Driven Piles Utilizing the University of Massachusetts Lowell static pile database, a limited number of case histories were identified for which a static pile load test in tension (pullout) Read the entire page →
From page 40... ... the testing method's performance and associated resistance factors, and (2) the number of tests that need to be carried out. Read the entire page →
From page 41... ... . This leads to the results presented in Table 24, which describes the resistance factors as a function of the site variability, number of piles tested, and target reliability. Read the entire page →
From page 42... ... "good quality" piles was taken to be nominal capacity. The probability chosen as a reasonable chance that such a set of good quality piles be incorrectly rejected as poor was taken to be 0.10. Read the entire page →
From page 43... ... Histogram and frequency distributions of Ksx for 80 cases of concrete piles in mixed soil. Read the entire page →
From page 44... ... For n/N less than about 10%, this frequency distribution can be reasonably approximated by the more easily calculated binomial distribution, (36) in which p = m /N is the fraction defective (Figure 44) Read the entire page →
From page 45... ... Dynamic Analysis Design WEAP Drivability Pile Stress Analysis GTR WEAP / Dynamic Measurements Load Factor Resistance/ Capacity GRL EOD – Default WEAP Analysis 1.656 ± 1.199 No. = 99 Construction No Dynamic Measurements WEAP Dynamic Equations Gates Equation 1.787 ± 0.848 No. Read the entire page →
From page 46... ... to the predicted capacity = KSX = λ =bias TABLE 17 The performance of the dynamic methods: statistical summary and resistance factors 0 0.5 1 1.5 2 2.5 3 Ratio of Static Load Test Results over the Pile Capacity Prediction using the CAPWAP method 0 5 10 15 20 25 30 35 40 45 50 55 60 N um be r o f Pi le Ca se s 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12 0.13 0.14 0.15 Re la tiv e Fr eq u en cy log-normal distribution mlnx = 0.233 σlnx = 0.387 normal distribution mx = 1.368 σx = 0.620 > Figure 28. Histogram and frequency distributions for all (377) Read the entire page →
From page 47... ... The recommended resistance factors represent the most significant attempt to date to develop LRFD code for deep foundations based on empirical data. 47 3.4.2 Static Analysis of Driven Piles Table 25 presents the recommended resistance factors to be used with static analysis of driven piles under compression, as well as the individual efficiency factor of each method, which indicates the method's relative economic merit. Read the entire page →
From page 48... ... 3.4.3 Dynamic Analysis of Driven Piles Table 27 presents the recommended resistance factors to be used for dynamic monitoring of driven piles and the relevant method's efficiency factors. The dynamic methods are categorized according to the controlling parameter and the time of driving. Read the entire page →
From page 49... ... The same criterion should be used for piles tested in tension, omitting the offset displacement of the elastic compression line. Drilled shaft capacity Resistance factors for a given reliability index β Capacity Component Soil Type Design Method Construction Method No. Read the entire page →
From page 50... ... . The recommended resistance factors should be applied to the mean capacity determined for all tests. Read the entire page →
From page 51... ... It should be noted that the results of this analysis should not be used for pile capacity prediction in the field. Table 27 provides resistance factors that should be used at EOD if WEAP analysis is required as a prediction method for pile capacity based on measured blow count. Read the entire page →
From page 52... ... 5. Resistance factors for static load tests of driven piles and drilled shafts should be assigned according to Table 30. Read the entire page →
From page 53... ... The data summarized in Figure 45 are used to demonstrate this issue. For example, the average static capacity analysis of a driven pile in clay results in a mean underprediction ratio of about 0.82 and 0.72 for α and λ methods, respectively. Read the entire page →
From page 54... ... 54 0 0.5 1 1.5 2 2.5 3 KSX = Ratio of Static Load Test Results over the Shaft Capacity Prediction using the C&K Method for Mixed Construction 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 N um be r of Pi leC a se s 0 0.02 0.04 0.06 0.08 0.1 0.12 R ela tiv e Fr eq ue n cy log-normal distribution mlnx = 0.101 σlnx = 0.494 mx = 1.229 σx = 0.509 normal distribution Figure 40. Histogram and frequency distributions for Ksx for 46 cases of drilled shafts in rock. Read the entire page →
From page 55... ... . 3.5.3 Sensitivity Analysis and Factors Evaluation The existing resistance factors of the AASHTO specifications for dynamic evaluation of driven piles are limited and connected to static evaluation methods. Read the entire page →
From page 56... ... Comparison between resistance factors obtained using the First Order Second Moment (FOSM) Read the entire page →
From page 57... ... , See Tables 7a and 8 for soil properties' correlations to SPT and CPT respectively, 36 = limiting friction angle, B = pile diameter 2B, 11.5B contributing zone to tip resistance. TABLE 19 Statistical details of static analyses of driven piles, resistance factors, efficiency factors, equivalent and "actual" factors of safety Read the entire page →
From page 58... ... Ct. = blow count; BP10cm = blows per 10cm TABLE 20 Statistical details of dynamic analyses of driven piles, resistance factors, efficiency factors, equivalent and "actual" factors of safety Read the entire page →
From page 59... ... F.S. x λ 34 Mixed 32 1.71 0.60 0.55 0.32 2.58 4.41 0.38 0.22 3.73 6.37 14 Casing 12 2.27 0.46 0.99 0.43 1.44 3.26 0.73 0.32 1.94 4.40 14 FHWA Slurry 9 1.62 0.74 0.38 0.24 3.69 5.97 0.25 0.15 5.70 9.23 34 Mixed 32 1.22 0.67 0.34 0.28 4.21 5.13 0.23 0.18 6.29 7.67 14 Casing 12 1.45 0.50 0.58 0.40 2.45 3.56 0.42 0.29 3.37 4.89 Sand 14 R&W Slurry 9 1.32 0.62 0.41 0.31 3.49 4.61 0.28 0.21 5.09 6.72 54 Mixed 53 0.90 0.47 0.38 0.43 3.70 3.33 0.28 0.31 5.02 4.52 14 Casing 13 0.84 0.50 0.33 0.40 4.23 3.56 0.24 0.29 5.82 4.89Clay 40 FHWA Dry 40 0.88 0.48 0.37 0.42 3.87 3.41 0.27 0.31 5.27 4.64 48 Mixed 44 1.19 0.30 0.73 0.61 1.94 2.31 0.58 0.49 2.42 2.88 23 Casing 21 1.04 0.29 0.65 0.63 2.17 2.26 0.52 0.50 2.70 2.81 13 Dry 12 1.32 0.28 0.85 0.64 1.67 2.21 0.68 0.52 2.07 2.73 12 FHWA Slurry 10 1.29 0.27 0.84 0.65 1.68 2.16 0.69 0.53 2.06 2.66 48 Mixed 44 1.09 0.35 0.60 0.55 2.36 2.57 0.47 0.43 3.02 3.29 23 Casing 21 1.01 0.42 0.48 0.47 2.96 2.99 0.36 0.36 3.92 3.96 13 Dry 12 1.20 0.32 0.71 0.59 2.01 2.41 0.56 0.47 2.53 3.04 Sand + Clay 12 R&W Slurry 10 1.16 0.25 0.79 0.68 1.79 2.07 0.65 0.56 2.18 2.53 49 Mixed 46 1.23 0.41 0.60 0.48 2.38 2.93 0.45 0.37 3.13 3.86 32 C&K Dry 29 1.29 0.40 0.64 0.49 2.22 2.86 0.49 0.38 2.91 3.76 49 Mixed 46 1.30 0.34 0.73 0.56 1.94 2.52 0.57 0.44 2.46 3.20 Skin Friction + End Bearing Rock 32 IGM Dry 29 1.35 0.31 0.81 0.60 1.75 2.36 0.65 0.48 2.19 2.96 11 FHWA Mixed 11 1.09 0.51 0.43 0.39 3.33 3.63 0.31 0.28 4.61 5.02Sand 11 R&W Mixed 11 0.83 0.54 0.30 0.37 4.67 3.88 0.22 0.26 6.55 5.44 Clay 16 FHWA Mixed 13 0.87 0.37 0.46 0.53 3.09 2.69 0.36 0.41 3.99 3.47 16 FHWA Mixed 14 1.25 0.29 0.78 0.63 1.81 2.26 0.63 0.50 2.25 2.81Sand + Clay 16 R&W Mixed 14 1.24 0.41 0.60 0.48 2.36 2.93 0.46 0.37 3.11 3.86 40 FHWA Mixed 39 1.08 0.41 0.52 0.48 2.71 2.93 0.40 0.37 3.57 3.86All Soils 27 R&W Mixed 25 1.07 0.48 0.45 0.42 3.18 3.41 0.33 0.31 4.34 4.64 17 C&K Mixed 16 1.18 0.46 0.51 0.43 2.76 3.26 0.38 0.32 3.73 4.40 Skin Rock 17 IGM Mixed 16 1.25 0.37 0.66 0.53 2.15 2.69 0.51 0.41 2.78 3.47 TABLE 21 Statistical details of static analyses of drilled shafts, resistance factors, efficiency factors, equivalent and "actual" factors of safety Read the entire page →
From page 60... ... EOD Resistance Factor φ/λ Pile Type Soil Type Design Method No. λ COV Redundant β = 2.33 Nonredundant β = 3.00 Redundant β = 2.33 Nonredundant β = 3.00 α-API 9 1.11 0.71 0.28 0.18 0.25 0.16 α-Tomlinson 9 0.95 0.57 0.33 0.23 0.35 0.24Clay λ-Method 9 0.72 0.52 0.27 0.20 0.38 0.36 β-Method 7 0.52 0.54 0.19 0.14 0.37 0.27 SPT-97 mob 7 1.18 1.33 0.08 0.04 0.07 0.03 Pipe Sand and Mixed αAPI/Nordlund 7 0.80 0.60 0.26 0.18 0.33 0.23 α-API 3 0.76 0.57 0.26 0.18 0.34 0.24Clay α-Tomlinson 3 0.64 0.54 0.23 0.17 0.36 0.27 β-Method 8 0.23 0.36 0.12 0.10 0.52 0.43H Sand SPT-97 mob 0.43 0.32 0.25 0.20 0.58 0.478 Target Reliability β Site Variation N Mean (λ) Read the entire page →
From page 61... ... 61 Fr eq ue nc y Fr eq ue nc y Pile Capacity Acceptance criterion x* Seller's risk Buyer's risk Distribution of unacceptable set of piles Distribution of acceptable set of piles Figure 42. Read the entire page →
From page 62... ... 62 2 110 0.01 0.1 0.90 0.05 Figure 44. Binomial nomograph for determining sample size, n, and permitted number of defectives, c, for contractor's risk α and owner's risk β (Montgomery 1991) Read the entire page →
From page 63... ... Soil Type Design Method Pile Type Redundant β = 2.33 Non-Redundant β = 3.00 Clay α-API, λ αTomlinson H, Pipe, PPC 0.25 1 0.20 H 0.15 0.10 β Pipe, PPC 0.25 0.20 Sand SPT-97 H, Pipe, PPC 0.25 0.20 Mixed α-API/Nordlund H, Pipe, PPC 0.20 0.15 TABLE 25 Recommended resistance and efficiency factors for static analyses of driven piles TABLE 26 Recommended resistance factors for static analysis of nontapered driven piles under pullout Read the entire page →
From page 64... ... = blow count; BP10cm = blows per 10cm Site Variability. Low Medium High Method EA CAPWAP EA CAPWAP EA CAPWAPNo. Read the entire page →
From page 65... ... TABLE 29 Recommended resistance factors for drilled shafts TABLE 30 Recommended resistance factors for static load tests Read the entire page →
From page 66... ... 0.72 53 0.81 51 0.83 52 Total 0.74 16 0.82 17 0.90 16 H 0.67 19 0.64 18 0.79 19 Pipe 0.76 18 0.87 18 0.81 17 Concrete λ α Tomlinson α API MethodPile Type Actual Mean FS for driven piles in clay α Method = 0.82 x 3.5 = 2.87 λ Method = 0.72 x 3.5 = 2.52 For Comparison CAPWAP - EOD 126 cases Mean = 1.63 BOR 162 Mean = 1.16 Actual FS EOD = 1.63 x 2.25 = 3.66 Actual FS BOR = 1.16 x 2.25 = 2.61 1.5 2 2.5 3 3.5 β - Target Reliability 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 φ R e s is ta n c e F a c to r Pipe Piles - α API 1 SD (17) Read the entire page →
From page 67... ... recommended α Method Exist λ Method Exist Actual Mean FS = 3.15 FS = 3.5 WSD Figure 47. Sensitivity analysis examining the recommended parameters for the design of concrete piles in clay using α API method. Read the entire page →
From page 68... ... 74 0.75* 74 Total 1.35 18 0.78 19 0.81 18 H 1.58 19 1.18 20 0.94 20 Pipe 1.21 36 1.10 35 0.61 36 Concrete SPT 97 βMeyerhof MethodPile Type Actual mean FS for driven piles in sand Range: pipe piles SPT 97 = 1.58 x 3.5 = 5.53 Meyerhof PPC = 0.61 x 3.5 = 2.14 * Read the entire page →
From page 69... ... recommended Actual Mean FS = 2.73 FS = 3.5 WSD Figure 51. Sensitivity analysis examining the recommended parameters for the design of concrete piles in sand using the β method. Read the entire page →
From page 70... ... 70 Resistance factor φ CAPWAP General CAPWAP BOR CAPWAP EOD AR > 350 BL ct. > 16 BP10cm Energy Approach EOD FHWA Mod Gates General 0.5 0.27 0 2.70 1.56 10.42 0.4 0 0 0 0 3.13 0.33 0 0 0 0 0.78 # of cases used 377 162 37 128 384 TABLE 31 Calculated probability of failure [p = (%) Read the entire page →

From page 33...

... 3.1.2 Driven Piles -- Dynamic Analysis 3.1.2.1 The Analyzed Cases Time of driving, driving resistance, and area ratio proved to be controlling parameters for the dynamic methods (section 2.5.3)