Bond beam (the longitudinal course that is typically required by code at the tops of walls) is usually just one course high (8".
Lintel (the longitudinal "beam" that occurs over window and door openings) can be any height required - maximum, I suppose, would be 4 or 5 courses, though usually you don't get that deep. We use 24" deep (3 course) lintels quite often but beyond that - rarely.
If you are an engineer, you should know that what you are requiring is not a bond beam. If you are not an engineer you better hire one. This is not a simple bond beam.
That does sound like a long span and heavy load for a reinforced cmu lintel. Consider using a cast-n place concrete lintel that is 8" wide or a steel lintel. Stiffness is going to be important as well as strength.
What you are dealing with is a reinforced masonry beam (a lintel is a specific type of beam). I would suggest studying Schneider and Dickey's book "Reinforced Masonry Design" published by Prentice Hall. Chapter 6 dicusses the design of masonry beams, with example 6-8 as a good illustration. I'm not aware of any limit on the depth of a masonry beam. In fact, Schneider and Dickey, chapter 7, has a section which discusses deep-wall beams which are walls that are simply supported, spanning across a gap at the bottom. One stipulation about a masonry beam is the requirement to provide lateral support equal to 32 times the least width of the compression area (97' UBC 2106.1.7). Another limit factor would be keeping the deflection of the beam less than L/600.
V23,
First I would use a steel beam. This is just my opinion, but I wouldn't use a bond beam that is over 32" deep (4 courses). Beyond that I think there is too much of a chance for the masonry lifts and joints to have imperfections that would limit the real capacity. Second I would use steel, as many above have suggested. I would also consider kicking the beam, if practical, to the roof structure in order to help the unbraced length. Third, how are you taking the lateral (wind/seismic) loads over the doorway? An 8" deep beam spanning 25' is way to long.
Fourth, I would look into arching action. If your roof is
high enough, say 13-15 feet over the top of the openning you can distribute some of the load into the jambs without having to support it with a lintel. Look into it in ACI 530 because there are some special conditions to consider.
Fifth, if you can't get a beam that is narrower than 7 1/2" to work, then talk to the architect and see if a 12" wide beam will work with the door hardware.
These are just some options. Let us know what you intend to do.
Bylar,
There are a lot of people who look here for information that can be helpful to them. A lot of those people are from throughout the United States, Canada and internationally working as engineers. Terminology is not something that is strictly universal to the profession and can very between locations.
What I am saying is take it easy on blasting people who post here. A lot of times they may be students or younger engineers who we should be here to help - not to scare away. We have a number of younger engineers at my firm and we always tell them to not be afraid of asking a question. If we blast people every time they post if they don't sound like they have the same level of expertise as us, then how helpful would we be?
Just my 2 cents worth. I'll get off my soapbox.
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