Pile Layout [SIG]
- Dogukan Kilic
- Melis Ceylan
Pile Layout
The Pile Group workflow item enables the definition of multiple piles under the same substructure within a single set of inputs, offering a more efficient method for defining the substructure components.
Substructure: Choose the substructure element associated with the pile group, such as end or interior bents, columns, or pile caps.
Pile Data[Grid (Rectangular)/Custom]: Specify the method of inputing pile group data. Selecting Grid (Rectangular) activates the number and spacing cells in the X and Y directions. If the pile grid is not rectangular, select the Custom and specify the piles individually.
Custom:
Longitudinal Offset: Employed to determine the position of the pile. Longitudinal offset along the Projected Grade Line (PGL), where 0 refers to the center point of the substructure above.
Transverse Offset: This parameter can be used to determine the offset value for the pile in the transverse direction, where a value of 0 places the pile at the center of the chosen substructure elements. A negative value will offset the pile to the left, and a positive value will offset it to the right when looking up-station along the PGL.
Batter Angle (Longitudinal): This parameter is used to rotate the pile along the alignment's longitudinal axis.
Batter Angle (Transverse): This parameter is used to rotate the pile along the alignment's transverse axis.
Number of Piles X (Along Station): Specify the number of piles along the station axis.
Spacing of Piles X (Along Station): Specify the spacing of piles (from one center to another) along the station axis.
Number of Piles Y (Transverse Direction): Specify the number of piles in the transverse direction.
Spacing of Piles Y (Transverse Direction): Specify the spacing of piles (from one center to another) in the transverse direction.
Pile Length/Section:
Section Length(Starts at bottom of footing): The top of the pile, which begins at the bottom of the footing, serves as the starting point for section definition. Users can define multiple rows to create sections with varying characteristics. The total length of the pile is calculated by summing the lengths of each row.
Start Section: The starting location of a section is determined by adding the lengths of all previously defined rows. If it is the first row, then the starting point is at the top of the pile.
End Section: The position of the end section is determined by adding the distance defined in this row to the sum of all previously specified rows.
Section Orientation: Rotates the pile section; when set to the default value of 0, the X direction in the section editor aligns with the longitudinal direction, while the Y direction represents the transverse direction.
Embed. Length into Substructure (Top pile portion): This value represents embedment length of pile into the substructure it is connected to. This value affects only 3D model and generated CADD drawings.
Pile Capacity: This value represents the compression capacity, and the axial force in the pile will be evaluated in comparison to it.
FEA
Depth of Fixity Method:
To model pile behavior linearly for pile foundations where soil-structure interaction is not a governing factor, the depth of fixity method can be used for simplified analysis. The effective length of the pile should be identified. This effective length represents the depth of fixity where the pile's bottom node is located with a fully fixed support. Depending on the goal of the analysis, the depth of fixity can be selected to either provide the correct peak pile moments or correct substructure stiffness. These options are beneficial for designing the piles and generating the correct force effects in the rest of the bridge structure, respectively. The pile FEA model is created as beam-columns with no support provided along the length. In OpenBrIM, this is achieved by selecting the Soil Spring Type as Linear Spring. Then, the engineer needs to identify the node locations and set all of them free except for the bottom one.
Soil Spring Type[Linear Spring/ Nonlinear Spring from the Soil Set]: This property allows the user to define the types of springs that are desired to be employed between the soil and the pile. For more details please refer to the Soil Structure Interaction page.
Soil Springs (Linear): If the Soil Spring Type is selected as Linear Spring, this tab should be activated. Then user can define the soil characteristics using fixities or linear stiffness values.
Offset from the bottom of the footing/bent: The offset from the bottom of the footing or bent parameter is used to determine the location of springs representing soil properties. For each row, the total distance to the top position should be entered. A node will be introduced at each location, and this length can also serve as a means to modify the pile's mesh.
Tx[Fixed/Free/Stiffness Value]: Translational stiffness along the longitudinal direction of the alignment. A nonzero or fixed value is generally employed to represent lateral soil resistance.
Ty[Fixed/Free/Stiffness Value]: Translational stiffness along the transverse direction of the alignment. A nonzero or fixed value is generally employed to represent lateral soil resistance.
Tz[Fixed/Free/Stiffness Value]: Translational vertical stiffness is employed to define axial soil resistance. A nonzero stiffness value or fixed is commonly applied at the bottom of the pile to represent the soil's tip resistance. If the user wishes to disregard soil side friction, a free condition can be applied at other locations; alternatively, if side friction should be considered, a nonzero stiffness value can be used.
Rx[Fixed/Free/Stiffness Value]: Rotational torsional stiffness is employed to define torsional soil resistance.
Ry[Fixed/Free/Stiffness Value]: Usually set to free, but users may input small values to address stability concerns in finite element analysis
Rz[Fixed/Free/Stiffness Value]: Usually set to free, but users may input small values to address stability concerns in finite element analysis
If the Soil Spring Type is selected as Nonlinear Spring from the Soil Set, OpenBrIM library will assign the appropriate spring properties to the pile. To generate these springs, following inputs are necessary, Section Type, Soil Springs from the Soil Set (Nonlinear), and Mesh Size.
Section Type[Circular, Rectangular, H-Shaped]: Specify the type of the section. This input will affect the effective diameter calculations that are needed by soil material models, unless the section is circular.
Soil Springs from the Soil Set (Nonlinear): Assign the Soil Set. Soil Sets are defined under the Soil Structure Interaction tab. For more information, please refer to the Soil Set page.
Mesh Size: Specify the length of the finite elements of the pile.
Top Connection[Fixed/Pinned]: Use this parameter to specify the connection type between pile and cap/bent.
Generate FEM? [Yes/No]: Setting the "Generate FEM" parameter to "No" can disable the analytical representation of the pile.
FEA - Group Effect
The effects of group interaction can be evaluated in OpenBrIM. The leading and trail rows must be specified based on the direction of the applied loading, and appropriate P-Multiplier values should be assigned accordingly.
Assign P-Multipliers[All Equal to 1/Custom]: By default, all P-Multipliers are set to 1. If the engineer needs to assign specific values, the Custom option must be selected.
Leading Row X (Along the Station)[Downstation/Upstation]: Specify the leading row along the station direction, based on the loading applied to the footing.
Leading Row Y (Transverse Direction)[Left/Right]: Specify the leading row in the transverse direction, based on the loading applied to the footing.
P-Multipliers for Each Row Lead to Trail X (Along Station): Specify the P-Multiplier values in the X direction for each row from the leading row to the trail row. This list must include values for every row in the X direction.
P-Multipliers for Each Row Lead to Trail Y (Transverse Direction): Specify the P-Multiplier values in the Y direction for each row from the leading row to the trail row. This list must include values for every row in the Y direction.