Load Cases – Design and Deflection
(Revised:
10/05/2022)
The Loading - Load Cases
screens in the Building Editor tree are used to define the specific Design
& Deflection Load Cases for all affected components of the building.
The column in the screen called “Origin” designates
whether the load has been System or User generated.
Each
screen displays the Load cases that will be applied to the applicable building
components (Frames, Bracing, Wall Secondary, Roof Secondary, Wall Covering and
Roof Covering) in the Building's Shape during the final design process.
Load
Cases are defined at the Project (Highest) Level for all building components and at the Shape Level for Frames, Wall
Secondary and Roof Secondary only.
Frame
Deflection cases and/or limits may be defined for each individual frame in a
shape in Frames / Locations (See below).
Secondary
Deflection cases and/or limits may be defined for each wall or roof surface
(See below).
Secondary
Deflection limits may also be defined for an entire string or an individual
segment at the Secondary/ Spaces level (See below).
Load Cases:
Note: Horizontal and Vertical Deflection Cases are combined when applicable
List
This grid list control is used to describe the
Building's Load Cases applied to the different categories or tabs (Frames,
Purlins, Girts, Bracing, Roof Panels, and Wall Panels).
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Notes:
The maximum
number of Load Cases is 800 on Solid
Web Frames and on Open Web Frames. There
is a maximum number of ten (10) Load Types that can be applied in a single Load
Case.
Revisions to Panel Types, Secondary Spacing,
Frames and Locations, Building Codes, or Loading Information, etc., will cause
the System generated Load Cases to be recalculated to reflect the revised
building definition(s). Load Cases with
an Origin of User, (a load added by an Engineer, or Builder that is not
included in the standard system Load Cases), will not be recalculated. System Generated Load Cases may only be
revised, but not deleted. Revising a
System Generated Load Case will cause the revised case to be generated as a
User Case and the System Case is re-instated.
System Generated Load Cases may be “turned off” or de-activated by
clicking on the “Do Not Use” checkbox.
Do Not Use: Allows the user to de-activate a Load Case such that
the component is not designed for that given Case.
Description: System generated
descriptions are the combined Load Type abbreviations. Any verbiage may be used that helps you
describe each user case.
Level: Design, Deflection, Special
or OMF - Connection. User Cases may be
defined for either Design or Deflection.
The software will generate Special or OMF – Connection Cases when
required for higher Seismic Design Categories.
Origin: System,
System Revised, or User. This column may
not be modified by the user.
Stress Factor: The Factor representing the
permissible increase in allowable stresses as permitted by the selected Code.
Def H: Horizontal Deflection
(Drift) limit. The maximum drift allowed
for a 20’ high frame designed with H/60 limit is approximately (12”/feet * 20’)
/ 60 = 4”
Def V: Vertical Deflection limit
defined as L/180 for the example shown above.
In this case the maximum deflection allowed for a 100’ clear span frame
is (12”/feet * 100’) / 180 = 6.67”.
App. Factor: The Application Factor
applied to the magnitudes of specific Load Types. For example, certain codes will only allow
60% Dead load to be combined with Wind uplift.
The App Factor in that case is 0.6*D.
Type of Load: Abbreviations representing the description of the
applied Load Type(s).
Insert a Row
This
button adds an empty row below the active (selected) row of data into the Load Cases
list. The user may create a Load Case by
entering data in each column in the created row.
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Notes:
A User Load Case
may also be created by simply revising a system generated Load Case and having
the software re-instate the original Load Case.
Tips: To delete a Load Type in a string, Tab over
to the required column, then hold down the Ctrl key while clicking the Delete
key. Entire rows of data may be Copied
and Pasted into newly inserted “blank” rows in the list.
Delete a Row
This
button removes the selected row of data from the Load Cases list. Only User created Load Cases may be deleted.
Mark ALL ‘Do Not Use’
This
button marks all Load Cases as Do Not Use at once. The desired Load Cases can then be turned
back on by clicking in the Do Not Use checkbox next to the row you desire to be
turned back on.
Use Load Case Reduction
If
the building qualifies for Load Case Reduction (LCR), when you first go into
the Load Cases dialog and check this box, the ‘eliminated’ cases will be marked
‘Do Not Use’ and will appear in their original order. After OK’ing out of the Load Cases dialog and
if/when you go back to that dialog, the ‘eliminated’ cases will all appear at
the bottom of the Load Cases list. LCR
is currently only working within the Frames, Bracing, and Roof Secondary
folders.
Crane Load Case Generation
If
the building has a Crane entered, then the code prescribed Load Case will be
automatically generated. If the user
desires crane Load Cases NOT to be generated, then uncheck the checkbox.
Load Case List at the Frame
Data Level:
Each
Frame will be designed for its own unique set of Load Cases. Load Cases depend on conditions affecting
that frame such as bracing, cranes, or mezzanines. The Load Case list for each frame can be
reviewed (read only, i.e. no revisions allowed) at Frames/ Data/ Shape/ Wall/
Frame Location/ Loading. The list will
include a new Level called Reaction that enables the software
to generate a Reactions Report for the frame.
Frame Deflection Load Case
by Frame:
Deflection
Cases and/or Limits may be defined for each frame in a shape. Go to the Frames/ Locations/ Shape/ Wall/
level and click on the Deflection Limits Column. Revise the Cases and/or deflection limits as
required.
The
check mark in the Defl Override column indicates that
there was a revision made to the deflection cases for that frame. The software will re-instate the system
default cases if the check is removed.
One
example when the deflection cases may need to be different for a subset of
frames is if a bay consisting of two frames supports a flexible suspended
ceiling and the two frames require a more stringent deflection limit than the
rest of the frames in the building. Another example when the deflection cases
may need to be different for a subset of frames is when supporting Hangar doors
in the end bay of a building where the deflection limits for the two frames may
be held to stricter limits.
Secondary Deflection Load
Case by Surface:
Define
unique Deflection Cases and/or Limits on a surface by going to the Secondary/
Default Information/ Shape/ Surface/ level and clicking on the Deflection Limits
tab.
Secondary Deflection Limit
by String and/or Segment:
Define
unique Deflection Limits on an entire secondary string by going to the
Secondary/ Spaces/ Default Spaces level and overriding the field called
Deflection.
Define
unique Deflection Limits on an individual secondary segment by going to the
Secondary/ Spaces/ Generated Spaces level and overriding the field called
Deflection.
Standard
Controls:
See also:
§
Surface Loading – Wall or Roof