b'YOUR TOOLKIT FOR BUILDING EXCELENCEroof above.In a typical post-frame building, withoutsystem are sufficiently stiff and strong and do not a second floor system, approximately 50% to 63%require help from the second floor diaphragm.of wind pressures on the sidewalls are taken downThe following are two design examples of post-into the foundation, while the remaining 50% toframe buildings that included a second floor or 37% are taken up into the roof diaphragm. Themezzanine. Since the focus of this article is on two-roof diaphragm collects lateral wind loads fromstory post-frame buildings, the design examples the sidewall columns and transfers the loads intoselected showcase a variety of options that can be the endwalls according to the stiffness relationshipused to frame a second floor while still working of all the involved components.This process isin conjunction with typical post-frame methods. discussed in Diaphragm Design of Metal-Clad, Wood-Frame Rectangular Buildings (ASAE EP484)Design examples-and referenced in the IBC.When a large secondExample 1: 60x120x22 Middlesex County Fair floor system is introduced, approximately 25% ofbuilding- The post-frame building was built in wind pressures on the sidewalls are transferred2013 by Tri-State Buildings, LLC of Stevens, PA. down into the foundation, while approximately 75%The building is used by the Middlesex County is transferred up into the floor and roof diaphragmsFair Association to store antique farm equipment. (see Figure 1-1 & 1-2).A large second floor systemThe building was designed under the 2009 IBC as may increase the lateral stiffness of the building andan S-2 use using VB construction. There is a large thereby reduce lateral deflections due to wind andu-shaped mezzanine in the building. The floor seismic loading.In the process of stiffening theframing consists of TJI floor joists supported by building, however, the shear loads in the endwallglulam beams and steel columns. The framing is may increase by 100 or more percent.To ensurealso tied into the sidewall of the building and is that the endwalls are not overloaded, it is notsupported by glulam columns found in that wall. recommended that the effects of the second floor(photos courtesy of Tri-State Buildings, LLC)system are ignored, even when the roof diaphragm and all other components of the lateral force resistingcontinued on page 26Figure 1-1 Wind pressure diagram in a single story post-frame building Figure 1-2 Wind pressure diagram in a two-story post-frame building FRAME BUILDER - JAN2020 / 25'