Function
- This function will enable the users to draw resultant force diagram along the member and generate a table, for the resultant forces (Fx, Fy, Fz, Mx, My, Mz) at several section-cut planes defined along the member. The section-cut plane defined using Section for Resultant Forces option can consist of plate/plane stress elements and/or beam/truss elements.
- This function is extremely useful for curved or skewed girder bridges which require modelling plate elements for deck. Resultant force diagram using plate and beam forces can be displayed for the defined virtual beams. Applicable analysis type is as follows: Static Analysis, Settlement Analysis, Moving Load Analysis (AASHTO STANDARD/LRFD, Eurocode, BS CODE 5400 & 3701, CANADA, PENNDOT, AUSTRALIA, and TAIWAN), Response Spectrum Analysis and Construction Stage Analysis.
Call
From the main menu, select [Properties] > [Section Properties] > [Section Manager] > [Section for Resultant Forces]
Input
Section for Resultant Forces
can be defined using any of the three modes described in detail below:
Mode: Select the procedure to define the section-cut planes for resultant forces.
Define the section-cuts for resultant forces, selecting the structure groups defined.
No. of Division: Number of members, the structure group has to be divided into.
The software divides the entire structure group into ‘n’ number of virtual beams with two section-cuts at the end of each virtual beam, where n is the number of divisions entered by the user. These section-cuts at the start and end of each virtual beam are referred to as virtual sections.
Define Virtual Section
Direction Vector
Align the virtual section’s local x-axis along the desired direction by clicking at two points in the model view or by entering the coordinates directly. Once the virtual section’s local x-axis is entered, local z-axis is determined parallel to the plane between GCS Z-axis and virtual section's local x-axis. If direction vector is not defined, local x-axis will be determined to the longest direction in GCS X-Y plane. Refer to 1.
Group
Select the structure group to be divided into virtual beams.
Click to define the virtual section. Centroid of each virtual section will be automatically calculated and displayed in the table. The calculated centroid reflects the area of beam and plate elements and various elastic modulus.
Click to change the Direction Vector, centroid coordinates, and the assigned nodes/elements of virtual section. Refer to
2.
Click to delete the selected virtual sections.
Define Virtual Beams
After clicking under virtual section definition, virtual beams are automatically generated for structure group mode.
If needed, the users can manually change the virtual section ID assigned to any virtual beam. Refer to 3.
Define the polygon cutting planes for resultant forces along the member.
Tolerance: Tolerance defining the polygon cutting plane. It is recommended to use default tolerance value for accurate results.
Define Virtual Section
Coordinate Input
Enter the GCS coordinates of the points necessary to define a polygon. User can manually enter the coordinates of the points or click in the entry field and then click on the nodes from the model view in the desired sequence to automatically enter the coordinates of the nodes making a polygon cutting plane. These polygon cutting planes are referred to as virtual sections.
Only the activated part of the structure is considered by the software while generating the virtual sections. Regardless of the sequence of node coordinate input, the local x-axes of the virtual section will be determined by Direction Vector. If direction vector is not defined, local x-axis will be determined to the longest direction in GCS X-Y plane.
Direction Vector
Align the virtual section’s local x-axis along the desired direction by clicking at two points in the model view or by entering the coordinates directly. Once the virtual section's local x-axis is entered, local z-axis is determined to the plane between GCS Z-axis and virtual section's local x-axis. If direction vector is not defined, local x-axis will be determined to the longest direction in GCS X-Y plane. Refer to 1.
Name
Enter a name, which will be assigned to the virtual sections generated at each end. The name can manually be changed from the virtual section table after adding the virtual sections.
Click to define the virtual section. Centroid of each virtual section will be automatically calculated and displayed in the table. The calculated centroid reflects the area of beam and plate elements and various elastic modulus.
Click to change the Direction Vector, centroid coordinates, and the assigned nodes/elements of virtual section. Refer to
2.
Click to delete the selected virtual sections.
Define Virtual Beams
Software automatically assigns an ID to the virtual sections generated. To define a virtual beam using two virtual sections, enter the virtual section ID in Define Virtual Beams table. Refer to 3.
Define the section-cuts for resultant forces, selecting the elements in the model view.
No. of Division: Number of members, the selected elements have to be divided into.
The software divides the selected elements into ‘n’ number of virtual beams with two section-cuts at the end of each virtual beam, where n is the number of divisions entered by the user. These section-cuts at the start and end of each virtual beam are referred to as virtual sections.
Define Virtual Section
Direction Vector
Align the virtual section’s local x-axis along the desired direction by clicking at two points in the model view or by entering the coordinates directly. Once the virtual section's local x-axis is entered, local z-axis is determined to the plane between GCS Z-axis and virtual section's local x-axis. If direction vector is not defined, local x-axis will be determined to the longest direction in GCS X-Y plane. Refer to 1.
Name
Enter a name, which will be assigned to the virtual sections generated at each end. The name can manually be changed from the virtual section table after adding the virtual sections.
Click to define the virtual section. Centroid of each virtual section will be automatically calculated and displayed in the table. The calculated centroid reflects the area of beam and plate elements and various elastic modulus.
Click to change the Direction Vector, centroid coordinates, and the assigned nodes/elements of virtual section. Refer to
2.
Click to delete the selected virtual sections.
Define Virtual Beams
After clicking under virtual section definition, virtual beams are automatically generated for Element Select mode. If needed, the users can manually change the virtual section ID assigned to any virtual beam. Refer to
3.
1
Virtual section’s local axis can be displayed from property Tab available under View > Display > Property tab > Virtual Section Local Axis.
2
If any change in elements' nodes assigned to virtual section is needed, the user can manually select or deselect the elements or nodes in the model view and click Modify. This will modify the centroid coordinates as per the new virtual section defined. Modify can be used to select or deselect the elements/nodes which is adjacent from the previous virtual section so that the program can automatically detect the new cutting plane.
3
The local axis of virtual beam is always oriented along ‘I’ end to ‘J’ end of the virtual sections enclosing the virtual beam. The orientation of local axis of virtual beam must be identical to the local x-axis of virtual section which can be modified using Direction Vector.
4
Specifically for curved bridges, users are recommended to use Polygon select mode due to following limitations.
1) Structure group mode may fail to generate the virtual sections when sections lie in a different plane longitudinally due to varying direction vector requirement.
2) Element select option may fail to generate a desired virtual section in case when the selected elements are not in a plane.
5
In one virtual section position excepting for the girder start and end, two virtual sections will be automatically generated for i-end and j-end.