Steel Reinf. Elastomeric Bearing [SIG]
- Umut Nuhat Sevinc
- Melis Ceylan
Articulation
The values that appear in these columns as soon as an insertion point is chosen are calculated based on the 3D geometry of the model. These values can be changed or kept as default. The calculations for these values can be displayed if the section related to ‘Elastomeric Bearing Stiffness’ under the category ‘Reports’ is defined.
Insertion Point: Used for specifying the bearing location and can be selected by using the three dots and the options ‘Pick...’ and ‘Select...’.
Tx[Fixed/Free/Stiffness]:When the bearing rotation is 0 degrees, Tx represents the stiffness in the longitudinal direction. It is typical for a continuous girder to have at least one fixed bearing (or to use a real stiffness value) in the Tx direction.
Ty[Fixed/Free/Stiffness]: Ty represents the stiffness in the transverse direction when the bearing rotation is 0 degrees.
Tz[Fixed/Free/Stiffness]: Tz represents the stiffness in the vertical direction. It is common to use a high stiffness value, such as 1000 kip/in, or to fix the bearing.
The documentation, which includes the stiffness values calculated and assigned to the object, can be obtained as follows
Specify the bearing to be reported.
Elastomeric Bearing Stiffness Spreadsheet View
Select the ‘DOCS’ icon from the left sidebar. Then, use the button next to the ‘Bearing Calculations’ title to access the Elastomeric Bearings report.
Rx[Fixed/Free/Stiffness]: Typically, bearings are free to rotate in the Rx direction.
Ry[Fixed/Free/Stiffness]: Typically, bearings are free to rotate in the Ry direction.
Rz[Fixed/Free/Stiffness]: Typically, bearings are free to rotate in the Rz direction.
Bearing Rotation: Curved decks can be guided either radially from a fixed point or tangentially to the radius of curvature. When the deck is guided radially, precise geometry is crucial for the bearings that are farthest from the fixed point. For structures with a constant curvature, it is recommended to align the bearings tangentially to effectively guide the deck around the curve as it expands and contracts.
Transfer Forces to Substructure [Yes/No]: If the user chooses to connect the superstructure to the substructure, a two-node spring is required between the pier cap and the girder, which can be generated by selecting “YES”. Conversely, if there is no substructure or if the abutments are being considered (currently, abutments in OpenBrIM have the "Generate FEM" option set to “NO”), the correct setting for the "Transfer Forces to Substructure" parameter is“NO” and one node springs are needed.
Bearing Bottom Elevation (readonly): The bottom location of the bearings in 3D, with respect to the Z-axis of the Global Coordinate System, is displayed to the user in this column, regardless of the alignment's vertical definition.
Elastomeric Pad
The Elastomeric Pad of the bearing can also be further modeled by defining the parameters below:
Geometry Type [Rectangular/Circle]: The elastomeric pad can be defined by its geometry, with two options provided: rectangular or circular.
Bearing Pad Dimension Perpendicular to Bridge Span: When defining the elastomeric pad's Geometry Type as rectangle, the Bearing Pad Dimension Perpendicular to Bridge Span can be specified. This refers to the dimension of the bearing pad in the transverse direction. Otherwise, when the circle option is chosen for the Geometry Type definition, this parameter will not be applicable (N/A).
Bearing Pad Dimension Parallel to Bridge Span: When defining the elastomeric pad's Geometry Type as rectangle, the Bearing Pad Dimension Parallel to Bridge Span can be specified. This refers to the dimension of the bearing pad in the longitidunal direction.Otherwise, when the circle option is chosen for the Geometry Type definition, this parameter will not be applicable (N/A).
Bearing Pad Diameter: If the bearing pad's geometry type is defined as a circle, this parameter is used to specify the diameter of the bearing pad. Otherwise, if the geometry type is defined as a rectangle, this parameter will not be applicable (N/A).
Number of Internal Elastomer Layers: The number of internal elastomer layers can be specified using this parameter. To see the representation of internal elastomer layers, refer to the figure above.
Thickness of Internal Elastomer Layers: The thickness of internal elastomer layers can be specified using this parameter.
Thickness of Exterior Elastomer Layers: The thickness of exterior elastomer layers can be specified using this parameter. To see the representation of external elastomer layers, refer to the figure above.
Steel Plate Thickness: The steel plates that exist with the elastomeric pad can be detailed in terms of their thickness, which can be adjusted using this parameter.
Side Cover of Pad: The thickness of the side cover pads can be adjusted using this parameter.
Elastomer Shear Modulus 'G': The elastomer shear modulus is a measure of the material's ability to deform under shear stress. It quantifies the stiffness of the elastomer in the shear direction, which is crucial for understanding how the bearing will behave under lateral forces, such as those caused by wind or seismic activity.
Elastomer Bulk Modulus 'K': The bulk modulus represents the material's resistance to uniform compression. It measures how incompressible the elastomer is when subjected to hydrostatic pressure. This parameter is important for evaluating the bearing's performance under vertical loads, ensuring it maintains structural integrity while accommodating compressive forces.
‘Kc’ Compression Stiffness (readonly): Compression stiffness 'Kc' indicates the bearing's resistance to vertical deformation under axial loads. It is a critical parameter in determining how the bearing will react to the weight of the bridge and any live loads, impacting the overall stability and serviceability of the structure. This parameter is displayed and calculated based on the inputs provided by the users.
‘Ks’ Shear Stiffness (readonly): Shear stiffness 'Ks' measures the bearing's resistance to lateral movement under shear forces. This parameter is essential for assessing how well the bearing can absorb and dissipate energy from lateral loads, ensuring that the bridge remains stable and safe during dynamic events, such as earthquakes or wind.This parameter is displayed and calculated based on the inputs provided by the users.
Plate Inputs-Visual
Plates of the bearing can also be further modeled by defining the parameters below:
Top Plate Thickness: The thickness of the top plate (in the Z direction) can be specified using this parameter.For visual representation, refer to the figure below.
Top Plate Length: The length of the top plate (in the longitudinal direction) can be specified using this parameter. For visual representation, refer to the figure below.
Top Plate Width: The width of the top plate (in the transverse direction) can be specified using this parameter. For representation, see the figure below.
Base Plate Thickness: The thickness of the base plate (in the Z direction) can be specified using this parameter. For visual representation, refer to the figure below.
Base Plate Length: The length of the base plate (in the longitudinal direction) can be specified using this parameter. For visual representation, refer to the figure below.
Base Plate Width: The width of the base plate (in the transverse direction) can be specified using this parameter. For visual representation, refer to the figure below.
Top Bolt Hole Diameter: The diameters of the bolts on the top plate can be adjusted using this parameter.
Top Bolt Edge Distance: The distances of the bolts to the edges in both the longitudinal and transverse directions can be specified using this parameter.
Anchor Bolt Hole Diameter: The diameter of the anchor bolt holes for the bolts placed on the bottom plate can be specified using this parameter.
Anchor Bolt Edge Distance: The distances of the anchor bolts placed on the bottom plate to the edges in both the longitudinal and transverse directions can be specified using this parameter.
Show Bolt Hole (Detailing) [YES/NO]: To display the bolts, this parameter should be set to ‘YES,’ and the DETAILING button on the top middle bar must be turned on.
Number of Segments Used to Draw the Bolt Hole: A higher number of segments results in a smoother display of the bolts. If this parameter is set to 3, triangular shapes of the bolts will be visible. As the number increases, the bolt geometry will be generated to more closely resemble a circular shape.
Capacity
Bearing Capacity: The bearing capacity can be adjusted using this parameter.