Bracing and Ties Tab

Use this tab to define vertical and horizontal diagonal bracing in the roof and walls, and to position longitudinal ties. A quick-generation option lets you populate whole systems without entering every member individually.

For bespoke layouts, turn on the Detailed Bracing Members List to edit individual members (types R/W/P, continuous C, transfer T, offsets, rotations, symmetry overrides, start/end positions).

Old Manual Entry

In the Bracing tab you can specify the positions of vertical and horizontal diagonal bracing in the roof and walls, and the positions of longitudinal ties. To shortcut entering every individual bracing and tie member, there is a quick generation option.

The Ties data entry area allows you to specify the positions where longitudinal ties are required, and their suggested section size. The bracing component is activated by the Y/N (Yes/No) input column. Note that the default is 'Y' if nothing is entered into the cells.

The Outer Eaves Ties places a tie at the external eaves positions.

The Inner Eaves Ties places a tie at the internal eaves positions. If you have a stepped frame, a tie will be placed at both the lower and upper eaves positions.

The Lean-To Ties places a tie at the lower and upper ends of the lean-to rafter. The Canopy Ties works in a similar manner.

The Mezzanine Ties places longitudinal ties at the intersection of the floor and column positions.

The Bracing data entry area allows you to specify the number of legs in each bracing system per column or span. You also have the option to reverse the direction of the bracing using the Rev (Y/N) column. You can also specify x- bracing by typing in an 'X'. 'S' is for a strut (compression only) or 'O' for only as tie (tension only). The first member starts normally in the outer frame. You can define a different number of bracing legs per main span by entering the numbers separated by commas. Therefore “8, 6, 8” will place eight legs in the first span, six legs in the second, and eight in the third. Section sizes are entered for each bracing system.

You may wish to share the wind loads between the bracing systems at each end of a building.

The Trans (Y/N) option allows you to insert longitudinal transfer members from the bracing system at one end of the structure to the bracing system at the opposite end. These transfer members are used in the analysis to share the longitudinal forces between the bracing systems, but are omitted in the design.

Tip: Giving each group of ties and bracing an individual section size will allow the program to design each group independently, otherwise they will be assumed to be in the same design group and will default to the same section size.

The ties and bracing are dynamically generated as each data area is filled.

Tip: Keeping the bracing tab in dynamic generation mode will allow the ties and bracing to automatically update every time an alteration is made elsewhere in the frame.

If you wish to edit the bracing manually, switch the Use Detailed Bracing Members List  off, and you will have access to the individual bracing member details. Note that if you switch this option on again the program will Regenerate ALL Bracing Members Using the Simple List above.

The above image shows data that is typically generated in the detailed bracing members list. First, the Bay Number in which the bracing is located, is entered, for example, “1”. If a tie runs the full length of the building you can enter 1 – 9 for the bay number (or whatever the number of bays happens to be).

Alternatively, typing “1-“ will tell the program to run the tie from bay 1 to the opposite end’s bay. The second entry refers to the number of the portal column involved, starting from the left portal column, for wall bracing and wall ties, or alternatively the span number in which the bracing occurs, for roof bracing and roof ties.

The third entry refers to the type of bracing or tie: Roof (R) bracing or ties, Wall (W) bracing or ties, and longitudinal ties between Props (P). These members are assumed to be pinned at the end connections. The (C) designated members are seen as continuous (i.e. not pinned), and therefore can be used with members that require fixed ends in the analysis, for example, crane beams. Finally, for longitudinal ties required to transfer forces between bracing systems (simulating the diaphragm action of wall or roof cladding and purlins/cladding rails), the (T) type ties should be used.

Note that all (T) designated members are dummy members used in analysis only, and no steel design briefs are created for them. The C and T designations can be used in conjunction with the R, W and P designations. For example, WT represents a wall tie member which will transfer load, but not appear in the design. PC could represent a longitudinal tie at prop level, continuous along several bays, with the ends fixed. The O represents an only as tie member (tension only), X represents x-bracing and M represents mezzanine beams.

The members entered here will follow the global or in-bay symmetry rules, depending on which symmetry options are active. These symmetries can be locally overridden by typing Y or N after the RWPC, or T bracing type designation. For example, WNN would indicate that the wall bracing is not mirrored globally, or in each bay.

The fourth column (Y1) is the start position of the tie or bracing member, whereas the sixth column (Y2) is the end position. For wall bracing and some of the ties, these values are in the vertical (y-axis) plane, and for roof bracing and most other ties the values will be in the horizontal (x-axis) plane. Note that it is not necessary to give full x and y coordinates, but just the positions along the member. Also note that the first x or y entry will be on the southernmost frame.

For drafting purposes you can offset the ends of the bracing. The program works on centrelines of members meeting at node points. Therefore the ends of bracing may be offset by, for example, 100 mm in order for the drafting to be correct at these positions.

You can also specify the section size and grade of the members and their rotational orientation. Inserting a value of “1” in the beta (PI/2) column will rotate the member by 90 degrees, “2” by 180 degrees, and “3” by 270 degrees.

You can enter any “Off Centre” eccentricity for a member. A value of 150 mm would offset the member horizontally from the member centreline by 150 mm, as shown below.

Any data entered can be added to or edited if required. The icons on the right hand end of the tab allow you to:

•insert a new line

•sort the lines of data by moving them up or down (arrows)

•remove lines (scissors)

•copy a line and then paste it elsewhere

Remember to highlight the line you wish to work on before taking any of these actions.

After the bracing has been automatically generated, you can edit the bracing data to suit your own particular requirements, using the editing facilities described above. Please remember that a cell may be relying on another cell above it, from which it is taking its data, and therefore altering data in a cell can affect other cells.

Tip: Clicking on any member takes you to the relevant tab and data line.