This page is devoted to frequently asked questions (FAQ) related to auto lateral loads.
Modeling and application
How do I assign wind auto-lateral-load conditions?
ANSWER: Wind auto lateral load may be assigned as follows:
- Define the wind auto lateral load.
- Assign wind-pressure coefficients using the Assign > Area Loads > Wind Pressure Coefficients option.
Is it possible to apply wind load to only a specific frame object?
ANSWER: Yes, wind load may be applied to specific frame objects through the process which follows:
- 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.
- Select Modify Lateral Load Pattern > Exposure from Frame and Area Objects > Include Frame Objects, and define wind-direction angle, along with other parameters.
- Designate the frame objects for wind auto-lateral-load application through Assign > Frame Loads > Open Structure Wind Parameters.
How is wind load applied per BS standard?
Extended Question: For modeling a
Floating Production Storage and Offloading
(FPSO) unit as a 3D frame system, how would I apply wind load per BS standard? The Wave Wind form is limited to API standard, and I'm concerned that diaphragm definition would affect analysis.
ANSWER: Two options are available, described as follows:
- Define dummy diaphragms then assign each to a single point object. Each point object then becomes the location where wind load is applied. Tributary area is specified using the Wind Exposure Width Data form.
- Alternatively, 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 menu.
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:
Display
Is it possible to display auto-lateral-load application?
ANSWER: Yes, auto lateral load may be displayed. The seismic auto-lateral-load pattern applied to structural joints, for example, may be reviewed in tabular format 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.
Formulation
How do I find the period used to calculate the auto-seismic load?
ANSWER: All parameters, including structural period, are reported in the table available through Load Pattern Definitions > Auto Seismic Load.
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