This page is devoted to frequently asked questions (FAQ) related to auto lateral loads.
Wind auto-lateral-load assignment
Question: How do I assign wind auto-lateral-load conditions?
Answer: Wind auto lateral load may be assigned as follows:
- Define wind auto lateral load
- Assign wind-pressure coefficients using the 'Assign' > 'Area Loads' > 'Wind Pressure Coefficients' option
Display auto-lateral-load application
Question: Is it possible to display (graphically or in tabular format) auto-lateral-load application?
Answer: Yes. For example, the seismic auto-lateral-load pattern applied to the joints of a structure may be reviewed in the table under 'MODEL DEFINITION' > 'Load Pattern Definitions' > 'Auto Seismic Loads' > 'Table: Auto Seismic Loads To Joints'.
Answer: Currently, it is not possible to display calculated wind pressures, though users may indirectly verify pressures by creating a test model. Assigning area-object exposure, for example, users may create a model with area objects located at different elevations and supported by lateral springs. Auto-lateral-load application of wind pressure on these area objects would yield spring displacements and reactions which correlate with applied pressure.
Diaphragm and area object exposure diagrams
Question: Would you please provide an example and diagrams showing how wind auto lateral load is applied given diaphragm and area object exposure?
Answer:
Local wind-load application
Question: Is it possible to apply wind load to only a specific frame element?
Answer: Yes. First, define a load pattern, designate the type as 'Wind', and specify the load as an auto-lateral-load pattern, such as with ASCE 7-05. Next, click 'Modify Lateral Load Pattern', select 'Exposure from Frame and Area Objects' > 'Include Frame Objects', and define wind-direction angle, along with other parameters. Finally, designate frame objects for wind auto-lateral-load application using the 'Assign' > 'Frame Loads' > 'Open Structure Wind Parameters' menu.
Wind auto lateral load on 3D frame structure
Question: For modeling a
Floating Production Storage and Offloading
(FPSO) unit as a 3D frame, how would I apply wind load per BS standard? The wave-wind form is limited to API, and I'm concerned that diaphragm definition would effect analysis.
Answer: Two options available include the following:
- Users may define dummy diaphragms and assign each to a single point object. Each point object then becomes the location where wind load is applied. Users may then specify tributary area using the Wind Exposure Width Data form.
- Alternatively, users may use dummy area objects to apply wind loads using exposure from area objects. This may be specified using the BS 6399-95 Wind Load Pattern form.
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This page contains frequently asked questions related to auto lateral loads.
General FAQ
Is it possible to review, in a graphical or tabular form, how is auto lateral load being applied?
Yes, for example, joint loads calculated from auto lateral seismic load pattern can be be reviewed in the following database table:
MODEL DEFINITION > Load Pattern Definitions > Auto Seismic Loads > Table: Auto Seismic Loads To Joints
It is not currently possible to display the calculated wind pressures, but you could set up a test model to indirectly verify the calculated pressures. For example, if you are using exposure from area objects, you could create a model that would contain area objects placed at different elevations that would be laterally supported by springs. Applying the auto lateral wind load to these areas and reviewing the spring displacements or reactions would enable you to back calculate what pressure is being applied to each area object.
Could you provide simple example with sketches of how the auto lateral wind load is applied for exposure from diaphragms and for exposure from area objects?
Can wind loads be applied to a specific frame member only?
Yes, this is possible. First define a load pattern of type Wind and specify that this is an auto lateral load pattern, such as ASCE 7-05. Then click the "Modify Lateral Load Pattern..." and select "Exposure from Frame and Area Objects > Include Frame Objects". Define wind direction angle and other parameters. Finally, use the "Assign > Frame Loads > Open Structure Wind Parameters" menu command to specify which frame objects should be loaded by the auto lateral wind load.
How can I apply auto lateral wind load to 3D frame structure?
Extended Question: I am modeling a 3D frame, module on an Floating Production Storage and Offloading (FPSO), and would like to apply wind loading according to BS standard. The procedure requires the definition of diaphragms, but would not this affect the analysis? I used the wave wind form but this is limited to API code.
Answer:
You have the following two options:
- You could define dummy diaphragms, each of which would be assigned to just one point object. This point object becomes the location where the wind load is applied. You can specify the tributary area on the [Wind Exposure Width Data] form.
- Alternatively, you could use dummy area objects to apply the wind loads using exposure from area objects. This can be specified on the BS 6399-95 Wind Load Pattern form.