Concrete repair with epoxy compound and strength calculation advice 1

[gerhardl]

What is the best way to repair below described case. What is the simplest way to calculate the strength of the repair? My role is to discuss this with a consultant/building specialist who is doing the calculations.

Case: The top deck of an all concrete parking house, with only one lower parking level, is also used for parking for private cars. Width is about 18 meter, supported by two rows of columns on the level below. The damage is limited to a transverse ‘expansion’ joint. The joint has a tongue and groove form, the tongue formed as a truncated triangle. Over time (Nordic climate, snow and ice) the concrete is crushed on topside, and partially broken away on underside (up to 10 cm width). The two jointed plates has partially a 2cm difference in level on underside (mid third). No further damage to concrete or cracks detected.

Some ten years ago two steel I-beams was installed as support, on the underside of the deck. The I beams run across the joint, placed on brackets on the two nearest columns to the joint. No deflection of the I-beams can be detected. The joint is now additionally proposed repaired by cleaning and filled with epoxy compound by a well renowned concrete repair company.

One of the problems is that the consultant has, for some identical buildings, described a repair method with concrete filling, reinforced with bolted steel plate across the joint on the underside.

We want to avoid this if possible, as it will cost more than the method described above. Target: Repair cost and consultant calculations as necessary, but as low as possible. Prove the strength.

All original technical drawings and calculations are accessible.

Any advice or comments?

 

[hokie66]

It is difficult to give you any advice without seeing the situation and/or the drawings. These are a few thing I would want to know:

1) What are the qualifications of the consultant? Is he a structural engineer?
2) Is the joint, which you described as an "expansion joint", supposed to be a movement joint? If so, do the steel beams now prevent this movement?
3) Was the tongue and groove joint intended to transfer vertical load? If so, that type joint is inherently defective.
4) How is the deck protected from the weather on the top side? Is there a membrane? Does the membrane cover the joint? Does the joint leak?

 

[Ron]

Agree with hokie66's questions. In addition, the joint was put there for a reason..movement. It sounds as though your consultant wants to bind the joint to prevent movement...not a good idea.

If I understand your description, the steel beams that were added do not bind the joint, but are moreso there to prevent excess vertical deflection of the joint, but as noted with your comment on faulting, they are doing nothing to help the middle part of the joint.

Do you know if the joint was doweled in addition to the joint key? Load transfer across an unsupported, keyed joint is very poor as hokie66 noted.

In general, more info is needed. A sketch or photos would be helpful as well.

 

[gerhardl]

Hookie66 and RON: Thank you. Helpful so far with your questions and comments! Will know more and probably get drawings. To expand with already known info:

1. He is structural engineer.
2. Original purpose would have been for moment, but perhaps unnecessary (unknown at the moment). Repetitive systematic failure point for at least four equal parking buildings. Two repaired, one under evaluation.

No, do not prevent the movement. Steel beams support the plates talking load from both sides of the joint ( And also middle? Wall innerside, 6m to beam/columns, 6m to next, 6m to outer wall.)
Steelbeams supported on brackets on columns in such a way that longitudal movement (temperature expansion) is possible. No direct binding to deck other than friction.

One of the reasons to suggest epoxy is that this is used for repair of concrete constructions exposed to seawater, will bind, seal and allow expansion.

3. Possibly,and assume not doweled. Some elastic material (10mm?) originally in joint, now detoriated.

4. Both endsides (each about 6m of total joint) is protected by wooden garages. Middle fully exposed to weater. Joint leaks, especially in middle section. No membrane or macadam.

5.In addition to epoxy top deck is proposed grinded down, repaired with 'roadpatch' and impregnated with 'water glass,.

I will revert with more later, and follow up with info.

 

[cvg]

these type of joints are often protected by a steel plate on the top side. but not bolted or intended to prevent movement. plating on the bottom side could trap water and possibly make the problem worse. filling expansion joints with rigid material or otherwise making them rigid is never recommended. identify the cause of the disintegration. sounds to me like de-icing salts and water intrusion. Repair as necessary, fill with an appropriate sealer and then keep the water out of the crack in the future

 

[hokie66]

In regard to your points:

2. I take it you mean the original purpose was for movement, not "moment". There is a big difference.

Epoxy is hard stuff, won't allow expansion if the joint is filled.

3. If there was elastic material in the joint and the joints were tongue and groove, vertical load transfer was either not intended, or the original designer was naive.

4. Sounds like a membrane is required. There must be other consequences of the leakage other than the joint deterioration.

5. Not sure about the patching and impregnating. Is "water glass" some sort of sealant?

 

[gerhardl]

Hookie66, Thank you so far!

Please let me update and correct myself!

2. Movement (of course).

3. Sorry, my (great) mistake! NOT Epoxy, POLYURETHANE! And this because of elasticity, bonding and strength!

4. The concrete is high-quality (c25), and leaking through detoriated joint only. 'Waterglass' is natriumsilicate, SiO2*Na2O, and will to some degree permanently impregnate upper 30mm concrete, said to be 70% water resistant for water penetration. (Macadamized top in addition might be evaluated)

5. It now boils down to to find a way to prove (or disappprove) that the cleaned and polyuretahne bonded joint is sufficient strong enough, together with the two I-beams to support deck and load. This without giving too high longitudal or transverse stretch on the upper side of the concrete plates. Plate is reinforced to take stretch on underside, rather than weaker armored upper side.

6. Alternative repair method is suggested to be cutting away damaged concrete to firm concrete either side. Re-armor and recast with concrete. New straight vertical joint, with new steelplate bearing: steelplate on underside one plate, bent 90 deg, vertical up and 90 deg other direction resting on opposite upper plate.

Last alternative (point 6) will cost more, and previous repair with I-beams, proven till now OK, is a lost investment.

We will of course select only a technically proven, lasting repair, regardless of cost level.

Comments anyone?