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I am reaching out to see if anyone can provide additional commentary, backstory, supporting information, studies, etc. regarding this statement in the commentary of ASCE 7-16 (the last sentence of Section C26.13), "Because of the great amount of air leakage that often occurs at large hangar doors, designers of hangars should consider using the internal pressure coefficients in Table 26.13-1 for partially enclosed buildings." It is interesting that this statement exists only in the commentary as it has a significant impact on the design of large aircraft hangars. Based on our findings and a review of the literature, we believe that this statement should exist in the body of the code rather than be limited to the commentary. Note that this statement appears as far back as ASCE 7-98 in the commentary.

It is our understanding that air leakage around the hangar door leaves at the design wind event will occur, as mentioned in the commentary, and based on our evaluation of several large hangars and various hangar door manufacturer's details. Leakage around the flexible weather seals of each door leaf on horizontal sliding hangar doors for Group I or Group II size hangars (hangar door heights of 28ft+ and hangar bay areas greater than 20,000sf) will readily exceed the maximum 4sf total opening requirement (or 1% of total wall area) for enclosed structures; thus, triggering a partially enclosed condition. This with the hangar doors fully closed. If, as called for in the commentary, air leakage at the hangar door seals is considered, the opening area calculations will most often result in a hangar with hangar doors fully closed to be correctly classified as partially enclosed.

For example: Using a 28ft door height, 140ft wide door opening, 6 door panels, and assuming a 1" gap around each door leaf = 39.66 sf. ASCE 7 does not offer guidance on the amount of gap to consider, but a 1" gap appears reasonable at the full design wind event when reviewing various hangar door manufacturer's details and taking into consideration building and hangar door movement, i.e., building racking, roof uplift, deflection of door system. A gap as small as 1/4" will trigger the partially enclosed classification. The Department of Defense acknowledges that there will be significant door leakage for large hangars based on the language in UFC 3-301-01 (October 2023). The UFC requires the hangar designer to classify the hangar as partially enclosed and to assume a 2" gap around each door leaf for calculating opening area around the hangar door leaves.

Thank you for the question and observation. As you note the commentary is too rooted in history to determine why it was placced in commentary, rather than provisions.  Regardless, I have forwraded your observation to the ASCE 7 Wind Committee for consideration of a possible move into the provisions.

I am reaching out to see if anyone can provide additional commentary, backstory, supporting information, studies, etc. regarding this statement in the commentary of ASCE 7-16 (the last sentence of Section C26.13), "Because of the great amount of air leakage that often occurs at large hangar doors, designers of hangars should consider using the internal pressure coefficients in Table 26.13-1 for partially enclosed buildings." It is interesting that this statement exists only in the commentary as it has a significant impact on the design of large aircraft hangars. Based on our findings and a review of the literature, we believe that this statement should exist in the body of the code rather than be limited to the commentary. Note that this statement appears as far back as ASCE 7-98 in the commentary.

It is our understanding that air leakage around the hangar door leaves at the design wind event will occur, as mentioned in the commentary, and based on our evaluation of several large hangars and various hangar door manufacturer's details. Leakage around the flexible weather seals of each door leaf on horizontal sliding hangar doors for Group I or Group II size hangars (hangar door heights of 28ft+ and hangar bay areas greater than 20,000sf) will readily exceed the maximum 4sf total opening requirement (or 1% of total wall area) for enclosed structures; thus, triggering a partially enclosed condition. This with the hangar doors fully closed. If, as called for in the commentary, air leakage at the hangar door seals is considered, the opening area calculations will most often result in a hangar with hangar doors fully closed to be correctly classified as partially enclosed.

For example: Using a 28ft door height, 140ft wide door opening, 6 door panels, and assuming a 1" gap around each door leaf = 39.66 sf. ASCE 7 does not offer guidance on the amount of gap to consider, but a 1" gap appears reasonable at the full design wind event when reviewing various hangar door manufacturer's details and taking into consideration building and hangar door movement, i.e., building racking, roof uplift, deflection of door system. A gap as small as 1/4" will trigger the partially enclosed classification. The Department of Defense acknowledges that there will be significant door leakage for large hangars based on the language in UFC 3-301-01 (October 2023). The UFC requires the hangar designer to classify the hangar as partially enclosed and to assume a 2" gap around each door leaf for calculating opening area around the hangar door leaves.

I am glad I found this discussion, because I came here to ask this exact question.  If it hasn't been presented to the wind committee yet, I would like to also add to what Jori said above:

• The statement "designers of hangars should consider using the internal pressure coefficients in Table 26.13-1 for partially enclosed buildings" is a little misleading.  It does not say to consider the building as partially enclosed, only that the designer "should consider partially enclosed coefficients."  I have seen this taken literally and a building be specified as enclosed but list a GcPi value of +/- 0.55.  Which can lead to some confusion and cause oversights.
• This statement exists in Commentary Section C26.13.  Commentary Section C26.12 states, "Whether doors, operable windows and skylights, and flexible and operable louvers are considered as openings depends on their intended use during a storm event."  This is contradictory to the statement that follows in Section C26.13.
• As Jori illustrated, the enclosure classification is typically quantifiable.  This recommendation, as stated, removes that clear definition.
• Some guidance would be good.  In Jori's example, which is an excellent example, she uses a sliding/rolling style of door.  How does this apply to other types of openings?  If it is a single panel door such as a hydraulic door, is it still to be considered partially enclosed?  How is this different than something like a truck dock, which has a series of individual coiling doors along one or more surfaces?
• Is air leakage such as this something that would cause the internal pressure of the building to change?  It was always my understanding that this provision was intended to account for a large opening on one surface which would allow a large volume of wind to enter the building but not escape.

Jacob R Ball, PE*

Manager of Segment Operations

BlueScope Buildings, NA

*licensed in Missouri, Kansas, and Florida

Thank you for the question and observation. As you note the commentary is too rooted in history to determine why it was placced in commentary, rather than provisions.  Regardless, I have forwraded your observation to the ASCE 7 Wind Committee for consideration of a possible move into the provisions.

I am reaching out to see if anyone can provide additional commentary, backstory, supporting information, studies, etc. regarding this statement in the commentary of ASCE 7-16 (the last sentence of Section C26.13), "Because of the great amount of air leakage that often occurs at large hangar doors, designers of hangars should consider using the internal pressure coefficients in Table 26.13-1 for partially enclosed buildings." It is interesting that this statement exists only in the commentary as it has a significant impact on the design of large aircraft hangars. Based on our findings and a review of the literature, we believe that this statement should exist in the body of the code rather than be limited to the commentary. Note that this statement appears as far back as ASCE 7-98 in the commentary.

It is our understanding that air leakage around the hangar door leaves at the design wind event will occur, as mentioned in the commentary, and based on our evaluation of several large hangars and various hangar door manufacturer's details. Leakage around the flexible weather seals of each door leaf on horizontal sliding hangar doors for Group I or Group II size hangars (hangar door heights of 28ft+ and hangar bay areas greater than 20,000sf) will readily exceed the maximum 4sf total opening requirement (or 1% of total wall area) for enclosed structures; thus, triggering a partially enclosed condition. This with the hangar doors fully closed. If, as called for in the commentary, air leakage at the hangar door seals is considered, the opening area calculations will most often result in a hangar with hangar doors fully closed to be correctly classified as partially enclosed.

For example: Using a 28ft door height, 140ft wide door opening, 6 door panels, and assuming a 1" gap around each door leaf = 39.66 sf. ASCE 7 does not offer guidance on the amount of gap to consider, but a 1" gap appears reasonable at the full design wind event when reviewing various hangar door manufacturer's details and taking into consideration building and hangar door movement, i.e., building racking, roof uplift, deflection of door system. A gap as small as 1/4" will trigger the partially enclosed classification. The Department of Defense acknowledges that there will be significant door leakage for large hangars based on the language in UFC 3-301-01 (October 2023). The UFC requires the hangar designer to classify the hangar as partially enclosed and to assume a 2" gap around each door leaf for calculating opening area around the hangar door leaves.