FRAME BUILDER - VOL7 NO3 / 35 
Wind pressure forces the entire door and frame into 
the building framing. Force transfer readily occurs 
through bearing at the door head and jambs. For 
wind pressure a line load from 10 percent of the 
door width is applied to each jamb column. A point 
load from the wind header is applied 12 inches above 
finished floor. The point load at each jamb is equal to 
1/5 the total wind load on the door. The remaining 
load is applied as a line load to the header at the top 
of the door opening. Most or all of the header load 
is transferred via bracing to the roof and ceiling 
diaphragm.
When wind suction is applied to a mono-fold door 
it pulls away from the building. The door will open 
unless latched to the building frame. Mono-fold 
doors are typically “latched” by locking the hydraulic 
rams. The door is stationary when the door is closed 
and “latched.” The door assembly can be treated as 
a rigid body when it is stationary. The doorframe is 
attached to the building frame along both jambs and 
across the head. This is an indeterminate structure 
since it is essentially a beam on an elastic foundation. 
Replacing the distributed reaction at each jamb with 
a resultant force simplifies the problem such that the 
equations of statics are sufficient for solution. The 
problem now becomes where is the resultant?
The shape of the distributed reaction along the 
jamb is dependent on the relative stiffness of the 
doorframe and the jamb column as well as the 
location of the cylinder to frame attachment. The 
stiffness of the tube steel doorframe is typically only 
a small fraction of the stiffness of the jamb column. 
Hence the distributed reaction concentrates near the 
ram attachment. Experience has shown satisfactory 
building performance when the building is designed 
with the jamb column resultant located at the ram 
attachment point. The designer can evaluate the 
appropriate location of the jamb resultant for specific 
door cases. The ram to doorframe / jamb column 
attachment point is a reasonable starting point.
Cane bolts located at the bottom edge of the door 
can be used in lieu of the locked ram latching 
system. Suction wind load is simply split between 
the head and the sill in this case. Assume locked 
ram latching unless otherwise specified by the 
door supplier and the owner is aware they must be 
continued on page: 36
YOUR TOOLKIT FOR BUILDING EXCELLENCE

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