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Pile LayoutThe 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:
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 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 in the transverse direction. Pile Length/Section:
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.
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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.