New Open Structure Wind Load

Added June 16, 2021 by Tekla User Assistance tekla.documentation@trimble.com

Software version: 
Tekla Structural Designer 2021

New Open Structure Wind Load

New Open Structure Wind Load

This new feature adds a quick and effective way to apply wind load especially for Industrial Structures which typically are not clad, though it can be used for any un-clad structure or part. Application is simple and straightforward - the existing Wind Wizard is used in essentially the same manner as currently, other than there being no requirement to ‘clad’ the model with wall and roof panels. The feature can also be used in conjunction with wind wall and roof panels and has a host of user-defined settings, making it very flexible and applicable to a wide range of structures and geometries. The method of calculation for open structure wind loads we have developed follows both general principles and guidance from the United States Loading code ASCE7 and the ASCE document ‘Wind Loads For Petrochemical And Other Industrial Facilities’ (adapted for all loading codes). For more information on using the feature and its load calculations, see the new Help Topic Open structure wind loads.

As shown in the picture below, the applied loads can be reviewed both via the decomposed loads in the Structure View (enable Text for Loading > Decomposed in the Scene Content settings to see values) and in the Wind View (for a selected direction and loadcase). In the Wind view, the principal wind load values of shape factor, wind pressure and applied wind force are reported in the cursor tooltip of a selected entity. All the applied loads are fully considered in analysis and design.

  • Scope:

    • Loaded Entities - Open Structure Wind Loads are generated on the following entities: Structural Members (beams, columns etc), Line Ancillaries, Area Ancillaries, Equipment (new for this release - see below).

    • Head Codes - applies to the United States, Eurocode (all countries) and Indian Head codes. It is not currently available for the British Standard BS 6399-2, or Australian AS:1170.2 wind code variants.

  • Assumptions & Limitations:

    • All wind loads are assumed to act perpendicular to the members, equipment and ancillaries.

    • Applicable for all 1D structural members irrespective of their characteristic except; Analysis elements, DELTABEAM, FABSEC beams.

    • Are not applied on structural walls (use wall panels over these to apply load).

    • Shielding effect is not considered.

    • Does not consider frictional wind forces on any surfaces.

  • Workflow - application of Open structure wind loads essentially requires two simple steps; 1) specify which entities the wind load will apply to 2) run the Wind Wizard and enable the new “Apply Open Structure Wind Load” It’s as simple as that! In more detail:

    • Review/ specify the entities to which the Wind Load is to be applied. This is controlled by a new Wind loading > “Apply open structure wind load” member/ entity property as shown in the picture below - when this is enabled the wind loading is applied.

  • You can carry out this step most effectively in Review View > Show/Alter State using the new “Wind Loading” attribute which enables rapid graphical review and editing of the setting. Simply Toggle or Set On/Off the setting by individual mouse click and/or Window cursor operations (see picture below).

  • The “Apply open structure wind load” property is enabled by default for Ancillaries and Equipment and is off for structural members.

    • Note that for continuous members it can be applied on a per span/ stack basis.

  • You can additionally review/ edit - via entity properties - the listed wind loading parameters Shape factor, Cf and Effective area XY and XZ factors. See below for more on these.

  • Run the Wind Wizard and check on the new “Apply Open Structure Wind Load” - from this point forward the process of completing the Wind Wizard and adding Wind loadcases is unchanged. Following this, the open wind loads calculation and application is entirely automated.

  • Additional aspects:

    • Review View - as mentioned above, Review View > Show/Alter State includes a new “Wind Loading” attribute enabling rapid graphical review and editing of the “Apply open structure wind load” property via Toggle or Set On/Off modes.

  • Shape factor (Cf ) and Effective area factors - new Global and Model settings are added to set the default values for these, accessed via Global/ Model Settings > Loading > Wind Loading as shown in the picture below. There are also Area/Length values for some ancillaries such as Walkways/ catwalks both with and without guardrails. Note the following:

    • The default Cf factors are taken from the document ‘Wind Loads For Petrochemical And Other Industrial Facilities’ published by ASCE.

    • The settings also have columns showing the Effective Area equations so you can see how these values are calculated.

    • Factor values set/changed in Model Settings are applied to all entities in the model. You can also set the value for an individual entity via its properties.

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