As an engineer with years of residential construction experience, I take the side of the contractor on this case. If I pushed back and made a contractor do extra work because a design was changed, I would have zero clients. I would ask for a formal calc package an tell them you are getting it...
Yes way overkill. To repeat JLNJ said, it only increases the reaction by 12.5%. However, why not ask the question (RFI, etc) prior to making the change to avoid all this mess? This seems common in residential construction; make the change, then ask if ok after.
Why a dropped steel beam if every clear inch matters to the owner? Upset a wood LVL beam in the truss space and use top chord intermediate bearing trusses. Or a flush LVL beam with hangers for bottom chord bearing trusses.
That blocking requirement isn't isolated to just NC. The same prescriptive wall bracing provisions are in the IRC2009 R602.10.6.2 for heel depths greater than 9 1/4".
You have a diaphragm with intermediate offsets (notches). If you are looking for a more in-depth analysis of how to design the transfer wood diaphragms around the notches, check out 'The Analysis of Irregular Shaped Structures - Diaphragms and Shears Walls' by Terry Malone. Most cases only...
Not sure if this will help, but check out http://treehouses.com/joomla/index.php/building-specifications-and-stress-analysis-report
This article describes story of the Out 'n' About, a treesort located in Takilma, Oregon and the process to verify the structural use of live tress.
Yes, most have out of plane load capacity, minimal though, and it puts the nails from the hurricane tie to the plate in constant withdrawal, which is not ideal. I would add another tie (or multiple ties depending on the amount of thrust) to the opposite side of the plate to rafter and verify the...
Without seeing the modular plans you are describing it is difficult to comment on the disparities between the modular plan girder layout and the tables in the IRC. Keep in mind the modular design is an engineered solution and won't exactly match the prescriptive IRC tables.
If by embedment, you mean footing thickness, then IRC403.1.1 states 6" thickness minimum. Chapter 7 of ACI 332-10 also covers residential applications for concrete footings and states similar requirements.
Check out the attached 'Dropped Header Design Guide' for additional information.http://files.engineering.com/getfile.aspx?folder=9b49fa83-6522-45ed-a9a9-210302db74b7&file=WIJMA_Dropped_Header_Design_Guide_(11-7-07).pdf
