Create joists

Steel joists, virtual joists, steel girders and virtual girders are specific member types used in the United States.

Steel joists are actual, physical, load-bearing structural members fabricated by a joist manufacturer. They are simply supported secondary members that, in turn, support slab and roof loads. Steel joists are constrained to standard types specified by the US Steel Joist Institute, and standardized in terms of span, depth and load carrying capacity.
Virtual joists are conceptual representations used for preliminary modeling and analysis. Their primary purpose is to allow the engineer to incorporate approximate properties of steel joists into the overall building structural model early in the design process.
Steel joist girders are custom designed trusses used specifically to support other members, most notably steel joists and virtual joists.
Virtual joist girders are conceptual representations of steel joist girders which provide approximate section properties to facilitate the initial modeling and analysis of the structure, especially when the joist girder's stiffness is significant.

All of the above can be created from the Joist list on the Model ribbon.

The process for adding, modifying, or deleting these joists generally follows the standard procedures for other structural elements in the software. Some of the processes are further outlined below:

Specify the joist type and section size

When creating or modifying a joist, you will need to define its type and section size using the Properties window or dialog.

On the Model ribbon, click the arrow under Joist to display the Joist and Virtual sub-menus.
Select the type required from the appropriate sub-menu:
- Joist > Standard, Special, or Girder
- Virtual > Standard, or Girder
In the Properties window, select Section, then click the arrow on the right side of section property.
In the list that appears, select <New\Edit...>
For Standard Joists, Special Joists, Virtual Joists and Virtual Joist Girders the Select Section dialog box opens.
1. Select the desired joist type and size.
2. Click Select.
For Joist Girders only, the Girder Section dialog opens.
- Enter the girder properties and then click OK.
- Click Add if you want to add another girder section.
In the Properties window, adjust the remaining parameters according to your needs.

Create a joist

Specify the joist type and size (as above).
Click the start point of the joist.
Tip: If you are using a point along a member, do the following:
1. Click the member to view its points.
2. Click the point that you want to use, or type the distance from the start of the member to the desired point.
Click the end point of the joist.

Move a joist

You can modify the joist position in both 2D and 3D views.

Select the joist.
Select the end node that you want to move.

Note: Ensure that only the desired end node is highlighted in the Select Entity tooltip.
Click the grid or construction point where you want to move the end node.

Tekla Structural Designer moves the end node to the selected point.

Joist properties

Properties are listed below in the order that they appear in the Properties window when an existing joist has been selected.


General
Name	The automatically generated name.
User Name	Can be used to override the automatically generated name if required.
Group	The name of the group to which the member belongs. See: Steel member design groups
Plane	Indicates the level or frame within which the member is placed.
Characteristic	Steel joist
Element type	Truss
Material type	Steel
Construction	Steel joist
Fabrication	Steel joist Virtual joist
Steel joist type	Standard Special [Only displayed for 'Steel joist' Fabrication type] Girder
Autodesign [Only displayed for 'Standard' Steel Joists. 'Standard' Virtual Joists and Virtual Joist Girders]	See: Steel member autodesign
Design section order [Only displayed when 'Autodesign' is selected]	The design order file from which a section size will be selected. For details of managing order files, see: Manage design section orders
Gravity only	When selected, the member is designed for gravity combinations only. When unselected, the member is designed for gravity and lateral combinations. See: Designing individual members for gravity only
Rotation	Rotation of the member about its local x axis. The default (0 Degrees) aligns the major properties with the global Z axis, (provided that the member has not been specifically defined within an incline plane).
Global offset end 1, end 2	Can be used to model a physical offset with respect to the global axes at one or both ends of the member, (exceptions apply). See: Member global offsets
Major snap level, Minor snap level	Defines the major and minor alignment of the member relative to the insertion point.
Major offset, Minor offset	Used to offset the member from the snap point in the major and minor axis.


Span
Name	The automatically generated span name.
User Name	Can be used to override the automatically generated name if required.
Section	The section size
Grade	Any of the available steel grades can be assigned to steel joists and steel joist girders, but a warning will be issued in the results for any grade which has strength other than 50 ksi. In Tekla Structural Designer an SJI VJ-50 steel grade has been provided specifically for virtual joists and virtual joist girders. This grade has properties similar to A992-50 steel, but with an increased density to account for the weight of web members and miscellaneous materials.
Linearity	Straight
Releases
Fixity end 1, end 2	Pinned only, apart from virtual joist girders which can also be set as Moment (pin Mz).
Torsional load release end 1, end 2	Check one end only to define a torsional release.
Wind loading
Apply open structure wind load	Select this option if you want open structure wind loads to be calculated. See: Open structure wind loads
Shape factor, Cf	The default shape factor varies according to the entity type and is taken from Model Settings > Loading > Wind Loading Default Cf factors are taken from the document ‘Wind Loads For Petrochemical And Other Industrial Facilities’ published by ASCE.
Effective area XY
Formula	The default effective area formula varies according to the entity type and is taken from Model Settings > Loading > Wind Loading
Factor	The factor used in the above formula can be edited if required.
Effective area XZ
Formula	The default effective area formula varies according to the entity type and is taken from Model Settings > Loading > Wind Loading
Factor	The factor used in the above formula can be edited if required.
Live Load Reduction
KLL	Specify the KLL factor in accordance with Table 4-2 in ASCE 7-05/ASCE 7-10. See: Overview of live or imposed load reductions
Deflection limits
Apply span\factor	With this option checked, the limit can be defined as a Relative span/factor.
Apply abs. limit	With this option checked, the limit can be defined as an absolute value.
Size constraints
Max depth, Min depth	Size Constraints are only applicable when Autodesign is checked. They allow you to ensure that the sections that Tekla Structural Designer proposes match any particular size constraints you may have. See: Size constraints
Instability factor
Prevent out of plane instability	Define if out of plane stability is prevented. See: Instability factor
End 1 / End 2
Apply SidePlate connection	Select to apply a side plate connection at the specified end(s).
Utilization ratio
Apply (to autodesign)	Selected - When an Autodesign is performed, the design will be incremented to achieve a utilization ratio less than the ratio limit. Unselected - When an Autodesign is performed, the design will be incremented to achieve a utilization ratio less than 1.0. See: Apply user defined utilization ratios
Apply (to check)	Selected - When a Check is performed, the check will pass provided the utilization ratio is less than the ratio limit. Unselected - When a Check is performed, the check will pass provided the utilization ratio is less than 1.0.
Ratio limit	The utilization ratio against which the autodesign or check is performed (when applied above).
Fire proofing
Protected	When Protected is selected, self-weight of the members is increased by the weight of fireproofing. See: Fire proofing
Exposure	Exposed on all sides
UDA
Name Finish Class Phase Note File	A customizable list of the attributes that can be applied to individual members and panels. See: Work with user-defined attributes