GGU-AXPILE: Design of Franki piles
The design of Franki piles is slightly different to the design of the other piles dealt with in the recommendations. The two example files provided, "Example B7 lower values.phl" and "Example B7 upper values.phl" contain the calculation for the corresponding examples in the EAP.
If you have selected the Franki pile in "Edit/Analysis options" and "Single pile" as the analysis type, you will see the following dialog box, which you can also access for Franki piles via the "Edit/Single pile" menu item:
Using the upper group box, the characteristic action of the pile is defined first.
The design load Ed is given by the characteristic action.
Ed = FG,k · γG + FQ,k · γQ
γG = partial safety factor for permanent actions
γQ = partial safety factor for changeable actions
This in turn gives the required, characteristic bearing resistance R1,k.
R1,k = Ed · γP
The characteristic bearing resistance R1,k comprises the pile shaft resistance Rs1,k and the pile base resistance R1b,k. The characteristic pile shaft resistance is calculated classically using the values from Tables 5.10 and 5.11 of the EAP, whereby the lower 0.8 m of the pile may not be adopted. The required pile base resistance R1b,k can now be calculated from this:
R1b,k = R1,k - R1s,k
Using the mean values for the CPT cone resistance qc or for the shear strength cu,k of the undrained soil and the required pile base resistance R1b,k, the required pile toe volume V can be determined from the nomograms in Figs. 5.5 to 5.10 of the EAP.
However, it is expressly pointed out that the pile base volume determined in this way is only used for draft design. The verification of the ultimate limit state must be carried out with the pile driving work performed on the final two metres of driving. Please refer to the notes in EA piles 5.4.5.3.
Beside the volume V the norm-driving work component W is determined.
W = Wactual/Wnorm
The norm-driving work Wnorm is given in Table 5.9 in the EAP for a variety of tube diameters. It is thus possible to determine the required driving work Wactual for the final 2 metres. The example file provided "Example B7 lower values.phl" contains the analyses used for the corresponding example in the EAP.
When the file has reached depth during manufacture and the actual driving work expended Wactual is known, the required pile toe volume V necessary to transfer the characteristic load Ed can also be determined. For this purpose, activate the "Verify using W" check box in the "Edit/Single pile" dialog box and enter the norm-driving work component W.
The program then calculates the required pile toe volume V.
In the case that the file is already complete and both W and V are known, also activate the "Specify pile toe volume" check box in the "Edit/Single pile" dialog box. First open the file "Example B7 lower values.phl", then enter the following values:
The program then calculates the utilisation factor µ for the characteristic load Ed.
µ = Ed/Rd
You will receive the result for the modified example.