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# minimum wind loads in the IBC

• To: <seaint(--nospam--at)seaint.org>
• Subject: minimum wind loads in the IBC
• From: "Schwan, Martin K." <SchwanMK(--nospam--at)ci.anchorage.ak.us>
• Date: Wed, 29 Oct 2003 17:32:28 -0900

Title: minimum wind loads in the IBC

There is quite a debate around out department regarding the calculation of the wind loading and I would like to generate some discussion with the list on this topic.

1.      Section 1609.1.2 of the 2000 IBC states the wind loads used in the design of the main wind-force-resisting system shall not be less then 10 psf multiplied by the area of the building or structure projected on a vertical plan normal to the wind direction (and similarly 10 psf is the minimum wind load for components and cladding and also for open structures) However, footnote c in table 1609.6.2.1(1) states if the pressure is less than 0, use 0 for the horizontal roof loads for the end zone and the interior zone for MWFRS.  It seems to me there is a contradiction between them.  What do you use and why.

2.      When the forces are developed do you apply them uniformly across the building width and then the average plf is applied to the shear walls [if you calculate the end zone width and the interior zone width multiplied by the appropriate height (gives area) times value in the table (psf) gives the resultant force in #s then sum the forces from both zones and divide by the building width to get average plf]  OR do you calculate the plf in the end zone and in the interior zone and then apply it to the tributary area and then distribute the force into the shear walls.

3.      If it worked out that the calculated edge strip (a) is 3 and therefore the width of the end zone is 2a = 6, and the building is 50 wide would there be a 6 end zone on each end and the width of the interior zone be 38?  See figure 1609.6(1) or would there be a 3 end zone on each end and the interior zone would be 54?

We put in a request for John Henry to come up in December but I wanted to get some direction in advance.  We do not have a consensus up here but we are trying to be consistent.  I really do appreciate and value your input and await your direction.  In the land of darkness, Martin