CMU non-conforming lintel beam / how serious an issue??
CMU non-conforming lintel beam / how serious an issue??
(OP)
Have a CMU 8" block wall going up.
You can see from the picture that the 15' wide opening has 1 precast lintel beam 8" deep. The plan calls for a 48" deep lintel beam with 3 sets of 2#5 horizontal rebars placed bot/mid/top of the beam.
48" of lintel beam was grouted and with all of rebar; however, the middle and top rebar and grout is discontinuous at the control joints (see picture).
Is this condition an issue?
You can see from the picture that the 15' wide opening has 1 precast lintel beam 8" deep. The plan calls for a 48" deep lintel beam with 3 sets of 2#5 horizontal rebars placed bot/mid/top of the beam.
48" of lintel beam was grouted and with all of rebar; however, the middle and top rebar and grout is discontinuous at the control joints (see picture).
Is this condition an issue?






RE: CMU non-conforming lintel beam / how serious an issue??
RE: CMU non-conforming lintel beam / how serious an issue??
RE: CMU non-conforming lintel beam / how serious an issue??
RE: CMU non-conforming lintel beam / how serious an issue??
RE: CMU non-conforming lintel beam / how serious an issue??
A couple of things to take into consideration:
1. Did the original analysis for the lintel take into consideration the control joints and evaluate the member for a uniform load or were the control joints not taken into consideration and a triangular load used in the analysis? With the control joints a uniform load should be used.
2. In order to take credit for the bars in the concrete lintel beam as the bottom bars in an overall 48" deep member the masonry and the concrete lintel have to work together. This means that there has to be a horizontal shear transfer across the interface between the concrete lintel and the first CMU course. Is this really occuring? It looks as if a mortar joint occurs on top of the concrete lintel so I suspect some transfer is occuring.
3. Check the dead load deflection of the concrete lintel under the weight of the total height of CMU + concrete lintel selfweight. Conservatively ignore any contribution of the CMU just to get a "feel" for the vertical displacement of the concrete lintel.
4. The entire shear is being taken by the concrete lintel. This has to be checked. Do you have certified drawings of the concrete lintel showing where the bars are located and the concrete strengths for the shear evaluation.
5. Check the bearing for both the concrete lintel and the CMU pier supporting the lintel.
RE: CMU non-conforming lintel beam / how serious an issue??
You can play with the flexure through arch action, but shear tends to control in a lintel. Add in the fact you have control joints right at the ends and the shear is probably 4 times the allowable. Maybe more.
RE: CMU non-conforming lintel beam / how serious an issue??
Did you specify the control joints? Bad CJ locations. A rake joint would have been better. On all the projects that I have done, I have never located any CJ's at that location, not even once. If the Architect shows them at that location, I would always insist on moving them to the mid-span of the lintel.
It seems that the wall blocks would get some sort of an exterior finish then if this is my job, I would suggest breaking them out to extend the horizontal rebars into the piers and put in the rake joints instead of the real CJ's, at least at the lintel depth.
RE: CMU non-conforming lintel beam / how serious an issue??
RE: CMU non-conforming lintel beam / how serious an issue??
As constructed, remedial measures, if not mandatory, would seem prudent.
BA
RE: CMU non-conforming lintel beam / how serious an issue??
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: CMU non-conforming lintel beam / how serious an issue??
jeff91 (Structural) asked
1. No. The CJs shown on the arch were for the brick, not the CMU.
2. A very good point to put in the data back for future reference.
Is this really occurring? It appears so.
3. EOR question.
4. Certified drawings of the concrete lintel from manufacturer but an EOR question.
RE: CMU non-conforming lintel beam / how serious an issue??
EOR needs to review and address this issue in writing. This could be a tear-out, depending on design capacity needed.
RE: CMU non-conforming lintel beam / how serious an issue??
RacingAZ was correct however, the horizontal rebar in the mid and top course should have been carried through the CJ and a raked mortar joint applied.
Two other 10-foot wide openings had, or were supposed to have had, 24-inch deep lintel beams; however, these were bisected dead in the middle by a CJ above a similar precast lintel beam.
Nor sure what if anything was done to correct the condition. I'll see if anything was ever put in the file.......
RE: CMU non-conforming lintel beam / how serious an issue??
Dik
RE: CMU non-conforming lintel beam / how serious an issue??