Sections [SIG]

Sections can be imported from a database and manipulated if needed, or the user can create a section by defining its shape and material and the following properties will be calculated by OpenBrIM.

Properties

The following properties will be used to compute the stiffness of the beams or trusses in the finite element analysis model:

Material: The material assigned to the section will be used to compute values such as the EI, GI, and EA for beam elements in the finite element analysis model.

Area: The gross cross-sectional area of the section is used for axial stiffness, and it is the only property needed for truss and cable elements since they have only axial stiffness. Rebars and tendons do not affect the computation of the area.

Shear Area Y: The shear areas Ay correspond to transverse shear in the xy planes with corresponding transverse shear stiffness as Ay*G. Rebars and tendons do not affect the computation of the shear area.

Shear Area Z: The shear areas Az correspond to transverse shear in the xz planes with corresponding transverse shear stiffness as Az*G. Rebars and tendons do not affect the computation of the shear area.

Torsion Constant: The torsional constant refers to the area moment about the member x-axis, and it is used to determine the torsional stiffness of the member. Rebars and tendons do not affect the computation of the torsion constant.

Inertia Y: The area moments of inertia Iyy about the member local y are used for the bending stiffness of beam elements. Rebars and tendons do not affect the computation of the inertia.

Inertia Z: The area moments of inertia Izz about the member local z are used for the bending stiffness of beam elements. Rebars and tendons do not affect the computation of the inertia.

Inertia ZY: The product of inertia (POI) describes an object's imbalance relative to a defined set of coordinate axes, but the current finite element formulation of feline in OpenBrIM does not consider Iyz (POI). When POI is not equal to 0 and the user rotates the section using the beta angle or the section editor, it can result in two different finite element analysis results. To ensure better representation of analytical problems, it is recommended to keep the value of Izy close to zero with the current feline formulation.

Compute Properties From Shape?[Yes/No]: When a section has geometry, selecting "Compute Properties from Shape Parameters" as "Yes" will automatically calculate the sectional properties. The properties shown in unlocked view will not be used. Users can view the computed parameters by using the lock icon. The inputs entered by the user for the area, shear area, inertia, torsional constant etc will only be used if "Compute Properties from Shape Parameters" is set to "No". Lastly, if the section does not have any geometry, the entered parameters will be used for the analysis, regardless of the "Compute Properties from Shape Parameters" setting. To summarize, in order to view the sectional properties that are used in the finite element analysis, users should use the lock icon. The sectional properties displayed with the lock icon will represent the properties used in the analysis.

Open

Unlocked Project

Open

Locked Project

Has Geometry? (readonly): If a section has shapes defined in the section editor, the "Has Geometry" property will be set to "Yes". Users can confirm this by accessing the three-dot menu and checking the shape from the section editor.

Assigned? (readonly):When a section is assigned to finite elements, the "Assigned" property will be marked as "Yes", although there may be cases where the section is also assigned to library components and indirectly used in the design and FEA process.

Is Composite? (readonly): A section will be defined as composite if the section is produced by a combination of two or more shapes and has the different materials assigned.

FAQ: Rigid Material and Section Definition

More Properties

Gross Area: The gross area of a section refers to the total cross-sectional area bounded by its outermost layers, including any voids or cavities within those boundaries. It is calculated without considering any deductions for holes, openings, or other internal features.

Radius of Gyration Y: The radius of gyration is a property in structural engineering that describes the distribution of cross-sectional area around a section's centroidal axis relative to its mass, and it is calculated using the section's area and moment of inertia. Although it does not affect analysis, OpenBrIM may use it for code check purposes in certain cases.

Radius of Gyration Z: The radius of gyration is a property in structural engineering that describes the distribution of cross-sectional area around a section's centroidal axis relative to its mass, and it is calculated using the section's area and moment of inertia. Although it does not affect analysis, OpenBrIM may use it for code check purposes in certain cases.

Centroid Location Y: Centroid of section. When defining sections in the Section Editor, the COG of the section may not align with the member reference x-axis, resulting in a centroid offset. To calculate the member offsets in such cases, a logic that includes both the centroid offset and the member end offset is used. A non-zero value for the centroid offset changes the member end offset values used in the feline stiffness matrix computation, thus affecting the FEA.

Centroid Location Z: Centroid of section. When defining sections in the Section Editor, the COG of the section may not align with the member reference x-axis, resulting in a centroid offset. To calculate the member offsets in such cases, a logic that includes both the centroid offset and the member end offset is used. A non-zero value for the centroid offset changes the member end offset values used in the feline stiffness matrix computation, thus affecting the FEA.

Shear Center Y: The shear center is used in certain design calculations, but it does not affect the results of the finite element analysis.

Shear Center Z: The shear center is used in certain design calculations, but it does not affect the results of the finite element analysis.

Perimeter: The perimeter of a section is utilized in some design calculations, but it typically does not impact the results of the finite element analysis. However, in cases where time-dependent staged construction analysis is employed with the CEB-FIP code, the perimeter may affect the coefficient computations per the CEB-FIP 1990 standard.

Warping Constant: The warping constant is used for design purposes and does not affect the finite element analysis results.

Non-prismatic Variation Direction[X/Y/Z/None]: The user only needs to input this value if they want to define nonprismatic variation. If the user intends to define nonprismatic variation, this input is optional. The nonprismatic variation direction X should be used for sections assigned to elements following the alignment in the longitudinal direction, such as girders. The Y direction should be used for sections assigned to elements in the transverse direction, such as pier caps, and the Z direction should be used for elements in the vertical direction, such as pier columns.

Extent

The Extent Tab’s parameters can be used to further define the section geometry.

Pos. of Neg. Edge Y: For a visual representation of Pos. of Neg. Edge Y , refer to the figure below.

Pos. of Pos. Edge Y: For a visual representation of Pos. of Pos. Edge Y , refer to the figure below.

Pos. of Neg. Edge Z: For a visual representation of Pos. of Neg. Edge Z , refer to the figure below.

Pos. of Pos. Edge Z: For a visual representation of Pos. of Pos. Edge Z , refer to the figure below.