This page addresses how to configure diaphragms to accurately generate wind loads. To model vertical (gravity) load with slope in roof configuration, please refer to Sloped Loads in LAVA.
Under ‘Building Definition’ - ‘Profile’ tab, you can set up universal Longitudinal and Transverse axes. LAVA defines a ridge along the longitudinal axis as default in the program. To speed up modeling process, it is advised that user aligns the main ridge of their structure with the longitudinal axis to take advantage of the default setting, and modifies secondary roof conditions as necessary in the following modeling procedures.
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We will walk through a simple example.
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The majority of the structural has slope roof, and the main ridge line is in X direction. Therefore, under ‘Building Definition’ - ‘Profile’ tab, set Transverse in Y direction:
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Select slope roof as default roof assembly.
Under ‘Building Definition’ - ‘Elevation’ tab, it will show a slope roof. Fill in the rest of the information that matches the majority of the building.
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For diaphragm that is align with the default setting, no additional configuration is needed after the diaphragm is modeled. See screenshot below, where the ridge is in X direction.
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How to setup a Gable roof/Hip roof?
There is a hip roof on top right corner.
X direction diaphragm, we can modify it as a gable roof with a ridge in Y direction. This will make sure the diaphragm will behave like slope roof in X direction.
Y direction diaphragm, we can model it as a mono-slope with a ridge in plan-south of this diaphragm.
Let’s start with the X direction:
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For diaphragm in X direction, under ‘Definition’ tab, check ‘use local roof setting for wind load’, select ‘Gable’ for Roof Type, and select ‘Y dir’ for Ridge Direction.
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The plan-south side of this diaphragm is blocked by another diaphragm, and won’t be subject to wind force. LAVA will automatically discard the wind pressure if the diaphragm on the plan-south is modeled.
If the diaphragm on the plan-south will not be modeled for some reason, we can make manual adjustment in ‘Basic Load’ - ‘Wind’ tab.
For ‘Side 0’, uncheck ‘Allow Wind Load on Leeward Surface’. The diagram on the right is updated for your reference.
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For ‘Side 2’, uncheck ‘Allow Wind Load on Windward Surface’. The diagram on the right is updated for your reference.
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How to setup a Mono-slope Roof?
We will continue to model the diaphragm in Y direction diaphragm for the roof at top-right corner.
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Under ‘Definition’ tab, check ‘use local roof setting for wind load’, select ‘Monoslope’ for Roof Type, and select ‘X dir’ for Ridge Direction, and select ‘S’ (south) for Ridge Location.
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How to setup a Flat Roof?
There is a flat roof at the right side of the structure.
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Under ‘Definition’ tab, input correct Roof Load Assembly Slope, check ‘use local roof setting for wind load’, and select ‘Flat’ for Roof Type. This flat roof does not have a parapet, therefore we will leave ‘Parapet’ unchecked.
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How to setup a Sloped roof with a parapet?
There is a sloped roof with a parapet on the top-left corner.
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Under ‘Definition’ tab, check ‘use local roof setting for wind load’, input correct Roof Load Assembly Slope, select ‘Monoslope’ for Roof Type, and select ‘X dir’ for Ridge Direction, and select ‘S’ (south) for Ridge Location. Check ‘Parapet’, and input correct parapet height above sheathing.
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