Bond Beam Lintel Combination? Masonry Shear wall pier?

[jgeng]

I have a small 1 storm masonry garage in florida. Plans call for or only one 8" bond beam at the top of the wall which will also span openings as a lintel including garage door. I believe the Florida Res. Code always requires a bond beam at the top of the wall. Reading the FRC which is based on the IRC it seams to me table R609.6.3.2(1) may apply but I am unsure, any opinions? My understanding of the different purposes are as follows: Bond beams have steel typically in the upper portion of the block or middle which is there for uplift forces, diaphragm chord tensile forces, and distributing point loads i.e. roof trusses, do you agree? Lintels strictly refer to members spanning opening and are often but don't have to be precast units. In any case even if the table doesn't apply I can develop the right design loads and design it as a doubly reinforced beam, just wanted to use the table if it applied? any thoughts?

Another topic: FRC (based on IRC) has prescriptive masonry shear wall tables and refers to footnotes about shear wall piers? they require elsewhere shear walls be no less than 2 ft in length? Do they have provisions somewhere to design a shear wall as a wall segment and pier combination?

 

[msquared48]

I suggest that you get ahold of the "Reinforced Masonry Engineering Handbook" by Amrhein and doing some selected reading. It's a very good reference for you structural collection, a must have.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[concretemasonry]

Jim Amrhein's book is great as a resource.

Although customary thoughts are that the steel in a bond beam is in the upper potion, there is no real code location requirement since it is intended to provide a "ring" around a building or in a wall. A bond beam may also function as an 8" deep lintel over shorter openings.

A combination of a 8" deep bond beam and 16" deep lintel (locally called horse collar, U-block, etc.) can be a very functional structural member using reinforcement draped to the bottom to provide maximum flexural strength while providing continuity.

Dick



Engineer and international traveler interested in construction techniques, problems and proper design.

 

[jgeng]

Thanks for the responses...I just ordered the reference. In this case I only have 8" vertical to work with. I need to span over a 9' opening and through a corner window with steel corner support post at midpoint/corner. Is there a code requirement for how far the lintels need to extend pass the opening? 2 ft? Do you find precast lintels are typically preferred? why? The precast lintel bottoms are solid so how would you extend your vert. wall reinf. at the opening edge into the bond beam/lintel? Thanks!

 

[hokie66]

I wouldn't try to drape reinforcement from top to bottom, but rather add bottom bars to suit. Precast lintels don't work well with vertical reinforcement, use the blockwork. With both top and bottom bars, you can get good fixity at the jamb where the wall continues, but not at a corner.

 

[HeavyCivil]

The Armhein text is great.

9' seems like a very long span for an 8" lintel.

While this doesn't sound like an option for you, grouting full the next course (or two) of CMU's above a bond beam (when it is not itself the top course) give you the same effect as providing a 16" U-block.

When required to probide bond beams at a specific maximum spacing (say 48") I try to influence the location of openings in the wall to utilize the bond beam as a lintel (doesn't really work well for windows but for louvers etc.)

 

[flgulfcoasteng]

Try

http://www.castcrete.com

for precast and prestressed lintels. Very common in Florida and they have a good page of simple design aides, articles, and specs:

http://www.ncmaetek.org/etek/homefrm_map.cfm?spdm=castcrete.com