Unreinforced masonry pilasters 1

[ACE58]

There were some unexplained cracks in the beam bearing areas of some of the masonry walls of a 2-story building that I designed. Many of these locations were designed with reinforced masonry pilasters (projected or flush-face). The second floor beams are set, the concrete floor has been poured & masonry construction was continuing to the roof level. The walls were x-rayed & the pilasters were found to be lacking vertical rebar or grout, or in some cases, both. This resulted in ALL pilasters being x-rayed. There were instances of discontinuous vertical bars or grout or totally unreinforced masonry throughout the job. The mason has since been fired & the construction manager has told the general contractor that everything must be corrected & to provide a solution. At this point, I am only being asked to review the proposed fixes, but I foresee being asked for my opinion on what to do. Truthfully, I've never encountered this degree of ineptitude & don't really have a "least destructive" course in mind. Has anyone out there been presented with a similar problem? Thanks in advance.

 

[pittguy12]

Ouch...

I guess the provisions for on site inspectors some clients/building officials require are around for a reason!

Short of having to replace them, is it possible you can sister the columns/pilasters up with either a concrete column or encase them with more masonry? I would guess space limitations will prevent this from being viable but I thought I would throw it out there.

Although I am not familiar with it, some of the rehab guys particularly on bridges and overpasses have started using fiber wrap to strengthen old concrete columns. I do not know if it would be overkill on something like this but it might provide the strength you need.

 

[hawkaz]

Where was the special inspector? This is one of the reasons that almost all masonry requires inspections.

As Pittguy12 indicated, you could consider Carbon-Fiber, but it's not cheap. Rebuilding may be more cost effective.

 

[dhengr]

Let’s see if I’ve got this right... you have a construction manager, general contractor, masonry sub, and other subs wondering around the site, all with their heads up their a$$es, and collecting their pay; but no body inspecting any of the work, even their own work, and they have the gall to ask you for a least destructive solution to their problems and construction errors which can’t even be seen, quantified or actually listed yet. Do I have that about right? They should all have been fired. You might also ask the AHJ what their bldg. inspectors get paid for. This job obviously needs a few more layers of inattentive and inexperienced management and bloated bureaucracy to make it run well and get done correctly. I’d suggest they hire a qualified Structural Engineer, who meets your, the client’s and the AHJ’s approval, to review and warrant their work, and offer solutions meeting the bldg. code and your approval. They should provide you with existing condition reports, calcs. and repair details, including means and methods and material; since the G.C. obviously can’t be trusted to manage his own project, even with the help of a construction manager. Also, they should pay for your extra effort on this project, since the client only paid you for the original design, which they chose not the follow. At this stage of the game, given what you suggest is the case, your job or duty is not to make it easy for them, at your or the client’s expense. It is to make sure they get it right, at whatever cost, and to make it look right too. Just make sure your design is not at fault. That you are responsible for.

 

[hokie66]

dhengr is correct, as usual. This situation can only be rectified by foot-by-foot examination of the masonry for missing reinforcement and grout, individual rectification details for each defect, and supervised construction of the repairs.

 

[ACE58]

Walked through the bldg. yesterday with the (2)CM field reps, (2) new masonry overseers & (2) masons. They will submit a detailed description for the fix of each pilaster. It boils down to providing temporary support for the structure while they break into the wall at each deficient pilaster & install bars & grout or break out the grout so that rebars can be mechanically anchored to the rebar in place. Each fix will be monitored & checked again after curing. All at no cost to the owner or architect/engineer. The contractors put up no opposition to these procedures & just want to get it fixed & move ahead. Thanks again.

 

[dhengr]

If you spend any extra time on this matter, you should bill the G.C. If you offer any improvements or simplifications which save time, money or finished appearance you should get a cut of that action too. If the pilasters aren’t even grouted, they will be pretty easy to open up and fix, maybe not even removing every face shell to do the needed work. If they are grouted, this could be pretty destructive demo. work, and maybe they should be left alone if reasonable well, but not exactly correctly, done. Instead, could you more easily grout and reinforce the conc. blks. immediately on either side of the pilaster and then just work on the top few courses of the pilaster, immediately under the beam, but to bridge and tie the entire system together under the beam. This would give you some sort of a weak stemmed T section pilaster. The top course may be a bond beam and I would work immediately below that to form my bridge beam btwn. the two reinforced side blks. And, I would reinforce this tie beam with upside down U formed bars down into the side blks. Just some quick, first, ideas.

 

[msquared48]

How are the pilasters going to be repaired considering any ties that may have been spec'd and omitted in the pilasters? Seems like this possibility could be more of a fix problem than the vertical bars to me.

Just curious...

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com