MPTE Model - Footing and Pile [MPTE]
- Dogukan Kilic
The MPTE Model is designed to generate multiple models using a single row of data. The goal is to create a reference model using the inputs under the Footing, Pile Geometry, and FEA tabs, as well as other workflow objects. Then, multiple models are generated using the inputs under the General tab. Therefore, creating only one row of data is sufficient to perform the analysis needed to find the critical length of the pile.
Based on the desired trial embedments, OpenBrIM creates multiple models and displays them all within the same project. This allows all trial lengths to be analyzed simultaneously, thereby reducing the overall analysis time.
General:
Top Elevation of Footing: Enter the reference location of the model. All other elevation values should be entered based on this value.
Final Embedment Length: Enter the final embedment length. This value can be higher or lower than the initial embedment length.
Number of Trial Lengths (Max 40): Enter the number of trial embedments that will be analyzed between the initial embedment length and the final embedment length. This value also indicates the number of models that will be created.
MPTE Load Cases: Specify the load cases that will be analyzed in the model. For details on load cases, please refer to MPTE Load Case.
Show/Hide Embedment Label[Show/Hide]: Enable this option if you want to visually identify which model correspond to which embedment length.
Initial Embedment Length: This is a read-only value calculated based on the inputs you have entered in your model. The displayed value is the pile length embedded within the soil. From a finite element standpoint, the pile is assumed to start at the center of the footing, so the footing thickness affects this value.
Unlike OpenBrIM bridge workflows, in the MPTE workflow, to import or generate sections and materials, the engineer needs to navigate to the FEA ā Properties tab in the tree view.
Footing:
Footing Type[Custom/Rectangular]: Specify the type of footing. The Custom option enables Footing Points, allowing for the input of arbitrary polygons. The Rectangular option enables Footing Width and Footing Length inputs.
Footing Points: Define custom polygons by providing the longitudinal and transverse locations of the points. For more details, please refer to Custom Foundation.
Footing Width: Enter the width of the footing, measured along the Global Y axis.
Footing Length: Enter the length of the footing, measured along the Global X axis.
Thickness: The thickness of the footing is also employed to define the shell element thicknesses in the analytical model.
Material: Material of the footing.
Rotation: This parameter is utilized to rotate the rectangular footing, with 0 indicating that it is perpendicular to the Global X.
Mesh Size: The maximum length of the shell elements representing the footing.
Pile Geometry:
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 refers the distance in the Global X axis,, where 0 refers to the center point of the footing.
Transverse Offset: Employed to determine the position of the pile. Transverse offset refers the distance in the Global Y axis, where 0 refers to the center point of the substructure above.
Number of Piles X Direction: Specify the number of piles along the Global X axis.
Spacing of Piles X Direction: Specify the spacing of piles along the Global X axis.
Number of Piles Y Direction: Specify the number of piles in the Global Y axis.
Spacing of Piles Y Direction: Specify the spacing of piles in the Global Y axis.
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.
FEA:
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
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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.
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