Vertical Bracing (Baseplate)

The Vertical Bracing (Baseplate) connection type is used for the design of bracing members connecting to a gusset plate which is in turn connected to a column baseplate. The connection can comprise of a gusset plate connected to the column only, or a gusset plate which is connected to both the column and the baseplate. The gusset plate(s) can be defined on one or both sides of the column and both gussets may connect to the column flanges or to the column web. Where bracing connects to the column such that gusset plates would connect to both the flanges and web, these have to be designed as separate connections using two design briefs.

When designing a bracing to column connection with an integrated Masterframe model, the basic bracing geometry will be determined by the Masterframe model, so determining the bracing and column section, the bracing angle and the connection forces. The input options can be used to refine the connection similar to designing a standalone connection.

The default layout of the Vertical Bracing (Baseplate) connection for a standalone connection is shown below. The initial bracing arrangement is for a left and right bracing connection to the column flanges. In the standalone connection, the initial set up has no bracing forces specified.

General

The General area of the property grid provides basic inputs for defining the connection brief and load case titles as well as setting inputs globally for this connection. The layout of the General area is shown below

Title - input the title for the connection design brief.

Load case title - input a title for the currently selected load case

Print Case - controls whether or not a load case will be available for printing

All plate grades - set the steel grade for all plates used in the connection. Click on the row to change the grade

Bolt Details - displays the current selected bolt grade and diameter for the connection.

The selected bolt grade and diameter apply to all the bracing connections within a single design brief. Therefore, it is not possible to set different bolt diameters for different parts of the connection within the one design brief. To define the bolt grade and diameter, the Bolt Details row is expanded by clicking on the arrow to the left of the row. The expanded Bolt Details area is shown below.

Bolt Grade - the bolt grade can be set by expanding the Bolt Grade row. This will reveal a drop down from which the bolt grade can be selected

Bolt Diameter - the bolt diameters are set by expanding the Bolt Grade row from which the required grade is selected

Hole diameter - the diameter of the bolts holes can be selected from the drop down option

Slip factor - set the required slip resistance factor using the drop down options

Base Plate Properties

The Base Plate properties area allows for the definition of the base plate width and thickness. The default area layout is shown below.

Depth - displays the current input base plate thickness in millimetres

Width - displays the current base plate width in millimetres. An input of zero gives a default width based on the column section size

The base plate width is relevant to the design of a gusset plate where the gusset is connected to both the column and baseplate. In this case, the forces in the bracing are resolved into horizontal and vertical force components. The horizontal force component is resisted by the weld between the gusset and base plate and so the width of the gusset and baseplate intersection determines the weld length and hence the horizontal shear capacity.

Column Properties

The column properties area allows the column section and grade to be defined. The column properties area also allows the column orientation to be defined to control whether the bracing members connect to the column about the major or minor axis. The layout of the Column Properties area is shown below.

Column Section - displays the current selected column section type, size and steel grade

Column Top Projection - shows the current projection of the column above the bracing connection. For display purposes only.

Brace on Minor axis - controls the orientation of the column/bracing interface. The column orientation is set by selecting the row and selecting the required option from the drop down

To select the column section, expand the row by clicking on the arrow. This will give the following additional options.

Each property can be amended by selecting each row. For the Steel Grade, Section Type and Section rows, this will activate a drop down indicator, which can be selected to expand the drop down to allow the required property to be selected. The cell depth input controls the beam depth for castellated or cellular beams. Using the mouse pointer, clicking in the right hand part of this row will allow the cellular beam depth by be manually input. This option is not used for Column Sections.

The connection design is limited to the bracing elements, gusset plates and welds. The column section is not checked as part of the bracing connection design and will need to be assessed independently of the bracing connection design.

Left Arrangement

The Left arrangement allows the user to define whether or not the connection includes a brace on the left hand side of the column when designing a standalone connection. For an integrated connection, the connection geometry is defined by the members in the Masterframe model. The left arrangement area is shown below.

To select whether or not the connection has a left hand brace, select the row and use the drop down to select the required option.

Left Gusset(s)

The Left Gusset area provides input to control the geometry and properties of the left hand gusset, where the connection is defined to have a left brace. The default layout of the area is shown below.

Each row controls the definition of the properties of the gusset or the welds between the gusset and the beam and column. The inputs for each set of inputs are accessed by expanding the relevant row by clicking on the arrow to the left of the row.

The expanded Left Gusset inputs area is shown below.

Auto Size - indicates whether or not the auto size option is active

Style - indicates the selected style of the gusset plate which controls the shape of the brace

Column Only Conn - indicates the selected option whether or not the gusset connects to the column only or connects to both the column and baseplate

Thickness - indicates the current gusset plate thickness

Brace clearance - the current defined minimum distance from the end of the brace to the beam or column

Bolt edge dist - the current set minimum edge distance for the bolts relative to the gusset edge

Perp to brace projection - indicates the defined projection distance between the edge of the brace and the edge of the gusset plate

The Auto size option uses the input minimum distances such as the bolt edge distance or the bolt geometry along with the brace setting out point and any horizontal or vertical offsets (see the Left Brace input area) to determine the geometry of the gusset plate. The size and shape of the gusset can be amended by turning off the Auto Size option. Doing so will provide the user with additional inputs. The Auto Size option can be turned off by selecting the Auto Size row and then using the drop down option to select 'No'. Once set to No, this input area modifies to provide input to determine the size of the gusset and chamfers. This modified area is shown below.

Auto Size - indicates whether or not the auto size option is active

Column Only Conn - indicates the selected option whether or not the gusset connects to the column only or connects to both the column and baseplate

Height - the current gusset plate height

Width - the current gusset plate width

Thickness - the current plate thickness

Offset - the current offset of the gusset along the member axis. The default is zero.

Top Left - the current dimensions of the top left chamfer

Top Right - the current dimensions of the top right chamfer

Bottom Right - the current dimensions of the bottom right chamfer

Bottom Left - the current dimensions of the bottom left chamfer

The welds on the gusset to beam and/or column can be defined by expanding the Left Gusset welds area. This is done by clicking on the arrow to the left of the row. The expanded area is as shown below.

Full butt weld - indicates whether the weld is a full penetration butt weld or not

Weld size - indicates the current weld size. An input of zero uses a default weld size based on the gusset thickness

Partial pen prep - indicates the depth of a partial penetration weld

If the Default weld type is set to use deep penetration butt welds rather than partial penetration butt welds with an overlay of fillet wield, the Left Gusset weld area will reflect this by including a deep fillet pen row instead of the partial pen prep row, as shown below.

Left Brace(s)

The Left Brace area provides inputs to control the parameters of the bracing on the left hand side of the connection. This includes inputs to define the section type and size along with inputs to define the bracing angle, bracing force and the setting out of the bracing and bolts. For bracing members design based on an integrated Masterframe model, the section size, forces and angle are determined from the frame geometry and the loads are taken the from the Masterframe loadcases.

The default display is shown below. The default layout is not expanded.

To expand the required row, click on the arrow to the left of the row. Each expanded area contains the same options for each available brace. The expanded top left row is shown below.

Section - indicates the current selected section type, section size and steel grade

Axial - the axial force in the bracing for the currently selected load case. Tension forces are input as a positive value

Angle - the angle of the brace measured from the horizontal

Brace Setting Out - input area to define the setting out of the brace member. The area is expanded by clicking on the arrow to the left of the row

Bolt Geometry - input area for the bolts connecting the brace. The area is expanded by clicking on the arrow to the left of the row

k comp. factor - the effective length factor for the gusset compression capacity check

The bracing member section is defined by expanding the Section area. This is done by clicking on the arrow to the left of the row. The expanded default area is shown below.

Steel Grade - displays the current set steel grade

Section type - displays the current section type

Depth (mm) - shows the current section depth

Thickness (mm) - displays the current section thickness

The steel grade is set by selecting the row and using the drop down to define the steel grade. The section type is defined in a similar manner, by using the drop down options to set the required section type. For standard sections other than flats, the section is chosen using a drop down list. When sections other than a flat is chosen, the Depth and Thickness rows will not be shown and instead a Section row will be displayed, as shown below.

The Brace setting out position and parameters are defined in the expanded Brace Setting Out area. The default area is shown below, which uses the member centrelines and the bolt distance from the nearest edge of the gusset as for the setting out.

Origin - displays the current set origin point. The default setting is to use the member centreline intersection points

Offset Horizontal - the current horizontal offset of the bracing centreline from the origin point

Offset Vertical - the current vertical offset of the bracing centreline from the origin point

End Location - displays the current setting to determine the end position of the brace as specified using the relative position of the end bolts

Bolt-Gusset Dist - displays the minimum distance from the outer most bolt to the out edge of the gusset (measured along the member axis)

The setting out dimension for the end location will change depending on the end location option chosen. For a bolt distance from the gusset option, the minimum distance from the last bolt row to the outer edge of the gusset plate is used. When the end location is set to use the minimum end clearance, then the dimension input required is the end clearance, and the last row of the Brace Setting Out area will change to reflect this.

Brace Setting Out Origin

The brace setting out origin is determined by the centreline of the bracing member and the intersection point with the member it is connected to. In a vertical brace to a column, the origin point for setting out is then the intersection of the bracing centreline with the column. The software provides two options to determine the origin point based on where the brace centreline intersects with the column. The origin can be defined to be the point where the brace centreline meets the column centreline, the Member Centreline(s) option, or the intersection of the bracing centreline with the outer face of the column flange, the Flange Intersection option.

Horizontal and Vertical Offsets

The horizontal offset allows the position of the bracing member to be offset horizontally relative to the origin point. The angle of the bracing remains as specified, thus the horizontal offset is a wholesale shift of the brace member horizontally. The vertical offset works in the same manner by shifting the brace vertically. Both positive and negative inputs can be specified. However, where the other input parameters control, it may not be possible to offset the bracing member by the specified amount. This can then result in changes to the overall connection geometry.

Since the brace position relative to the gusset plate is determined not only by the origin point and both the horizontal and vertical offsets, but by the end location setting and minimum end distance as well as the specified minimum brace clearance value, amending the horizontal and/or vertical offsets can result in a change in the relative positioning of the brace member relative to the origin as well as resulting in a change in the size of the gusset plate itself.

Since both the horizontal and vertical offsets affect the positioning of the bracing relative to the intersection of the brace centreline and column centreline, specifying a horizontal and/or vertical offset will result in additional moments being generated in the main column. These forces are shown in the calculation outputs.

The bolt geometry for the brace connection is defined by expanding the Bolt Geometry area. This is done by clicking on the arrow to the right of the Bolt Geometry row. The default area layout is shown below.

Bolt Rows - displays the current defined number of bolt rows

Row Spacing - displays the current set bolt spacing dimension. The bolt spacing is specified in millimetres

Bolt columns - displays the number of bolt per column

Column Spacing - indicates the spacing of the bolts in each column where multiple bolts have been defined in the Bolt Columns input.

Edge distance - displays the current edge spacing for bolts. An input of zero means the bolts will be aligned on the brace centreline when there is a single bolt per column

End distance - shows the current end distance from the end of the brace member to the first column of bolts

Staggered bolts - displays the current setting for the bolting pattern

To amend any of the above parameters, select the required row and then either input the required value or, in the case of the Staggered Bolts, use the drop down to select the required option.

k comp factor

The k comp factor input provides the ability to specify the effective length factor for the compressive strut design for a gusset plate where the bracing member is in compression. This input is used where the bracing arrangement or bracing member type does not fall into the scope of Section 8.5 of SCI P358.

Right hand bracing

The input areas for the right hand bracing are the same as for the left hand side, with input areas to allow the definition of the right hand bracing arrangement of brace and gusset members and a right hand beam, along with inputs for the bracing member section type and size and bracing geometry. For details of the use of the right hand input areas, see the corresponding left hand inputs detailed above.