×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Topping Bond Strength on Precast Double tees

Topping Bond Strength on Precast Double tees

Topping Bond Strength on Precast Double tees

(OP)
What minimum bond stregth should I specify for a new parking garage, for the cast-in-place concrete topping that will be poured on top of the new precast prestressed double tee units that will have a deliberately roughened surface? I believe that CSA A23.1 gives a minimum bond strength for toppings of 1.0 MPa (145 psi) but I was wondering if anyone has experience with this, what bond strength is generally obtained when the topping is placed on deliberately roughened tees, and whether I can specify something > 1.0 MPa (perhaps 1.5 MPa) without encountering push-back from the contractor. A greater bond than 1.0 MPa might be desirable, given that this is a roof level open air parking subject to the full summer to winter temperature variation of minus 20 deg. C to plus 35 deg. C in this area.

Also, is there any surface prep required beyond the deliberately roughened surface and a saturated surface dry condition before placing the concrete?

Is any bonding agent used, such as a rich cement slurry scrubbed into the surface of the roughened tee? I think not, but I am not sure.

RE: Topping Bond Strength on Precast Double tees

Ajk1... Instead of specifying a bond strength why not specify tensile bond test and require the failure to be in the substrate not at the bond interface. This assure you that the bond strength is at least as high as the tensile strength of the precast

RE: Topping Bond Strength on Precast Double tees

(OP)
Ron - that would force it into a bond strength of about 3 MPa which is much greater than the CSA A23.1 requirement of 0.9 MPa minimum. I would be concerned that to set such a high acceptance criterion would require a bonding agent, perhaps an epoxy bonding agent (even then we may not consistently achieve it), and we would get push-back against this from the contractor. I am wondering what the industry practice is for bond strength of topping on precast tees for parking structures, or is it not checked on each project?

RE: Topping Bond Strength on Precast Double tees

Ajk1....rarely checked in my area

RE: Topping Bond Strength on Precast Double tees

It's never checked in my area either. A roughened surface is really all that is typically used. Any debris lying on the surface of the tees should be blown off before casting topping.

BA

RE: Topping Bond Strength on Precast Double tees

(OP)
ok, thank you both.

RE: Topping Bond Strength on Precast Double tees

I don't even know how you would measure it, as I doubt it is ever attempted. I would avoid bonding agents, and they can easily turn into debonding agents if the timing is not exact.

My bigger concern would be waterproofing. How do you intend to make this type of deck watertight?

RE: Topping Bond Strength on Precast Double tees

(OP)
to hokie66 - there is a Canadian Standards Association (CSA) Standard A23.2 that covers how to do the bond test. Basically drill a 3" diamter core thru the topping and a bit into the substrate, then epoxy a plate to the concrete; special testing device that pulls up, is screwed onto the plate' The device has a gaiuge that measures the pull force. It is a very common test here and all of the Canadian testing agencies that I have worked with know how to do it. I have had hundreds of these tests done over the last 30 years. I think ASTM may have a simialr test.

The precast form of parking structure construction with cast-in-place topping is popular in North America, but it is very specialized and the precaster has to know what he is doing and have the experience.

It is watertight by virtue of the uncracked prestressed double tee units, and the caulked joints in the topping which are located at the edges of the tees. These caulked joints do require some maintenance over the years, but in general (with some exceptions) they have perfromed reasonably well. I take it from your comments that it is not used in Australia, where I take it is your territory.

RE: Topping Bond Strength on Precast Double tees

No, these type of parking garages are not used in Australia, at least to my knowledge. The prestressed precast industry here is not very prevalent in buildings, only in bridges. Not sure, but I believe there would be building code provisions which would prohibit dependence on caulked joints in roof structures.

RE: Topping Bond Strength on Precast Double tees

ajk1...similar to the ACI test. I've done them probably a dozen times in 30+ years.

RE: Topping Bond Strength on Precast Double tees

What happens if the topping concrete meets or exceeds f'c but fails to meet specified bond strength? You ask the contractor to remove and replace the topping?

BA

RE: Topping Bond Strength on Precast Double tees

(OP)
hokie66 - yes the caulked joints are the weak link in the system. If they develop a leak that is not repaired, then major damage can be done to the structure including the tees, which are for practical purposes almost impossible to repair. It is not my favourite way to design a garage, but it is permitted by CSA S413 Parking Structures, and with the proper maintenance they have generally performed satisfactorily. If it is a foolish owner who does not maintain it properly, and does not realize that it is cost effective to do leakage repairs as soon as possible without delay, then it will have a limited life. I have heard in recent years some engineers may want to put a traffic topping waterproofing membrane on the concrete topping, but then the cost advanatge over cast in place disappears. Many of the shopping centre garages around Toronto have this precast system (without a membrane) but when I looked after the structural design of the 9300 car parking structure at the Toronto airport new terminal 1 a number of years ago, I recommended against this system and it was built as cast-in-place (as are many other large airport garages).

BAretired - same as for any other aspect of construction that does not meet spec. As you know, usual procedure is to do the calculations to see if spec can be relaxed. If it cannot be relaxed, then yes the topping would have to be removed or perhaps an extended warranty could be sought so long as the structure had the required strength and there was no life safety issue. However, my understanding is that it is no problem to meet the required bond strength and it would fail only if really bad practices were used on site, in which case the contractor deserves to pay for its removal. Some bond strength tests should be done as soon as possible after the first area of topping is placed so that any general problem will be detected as soon as possible. I don't see the point of CSA specifying a minimum bond strength, if no testing is done on site to verify that it is being achieved.

RE: Topping Bond Strength on Precast Double tees

In New Zealand you are allowed to add reinforcement in the Double Tee flanges to increase the longitudinal shear capacity at the precast/in situ interface. Typically this consists of spirals of 6mm plain bars about 100mm diameter, length to suit your needs. They are usually placed over the ribs. I'm assuming your code specifies the minimum bond stress to ensure there isn't a longitudinal shear failure and the topping delaminates.

RE: Topping Bond Strength on Precast Double tees

(OP)
Agent666 - I understand what you are saying, but generally it is not necessary to add interface rebar for parking garage spans and loads (2.4 kPa). In most of Canada, that would be counterproductive because it would put more rebar in the cast-in-place topping where it would be eventaully subject to corrosion from the de-icing salts tracked into the garage in winter, which are absorbed into the pore structure of the concrete. I am guessing that is not an issue in most of New Zealand...so thanks for identifying where you are.

RE: Topping Bond Strength on Precast Double tees

ajk1,
After the Elliott Lake collapse, I wonder if the Canadian authorities might be having second thoughts about relying on maintaining sealant joints as a means of waterproofing.

RE: Topping Bond Strength on Precast Double tees

(OP)
The double tee garage with caulked joints and no membrane is used throughout North America, not just in Canada, and there are currently no plans to revise the parking garage standard. Double tee garages have a reasonably good track record thoughout North America. I don't know if they are used in Europe. So best not to jump to conclusions before knowing the facts.

A few facts:

- Each parking garage system has its pros and cons, and each type has had its horror story. Eliott Lake is only the most recent horror story.
- Elliott lake was NOT a precast double tee system.
- Eliott Lake was a precast hollow core system - something I would never use.
- It had been leaking for 30 years with no repairs.

Do you know of any garage, irrespective of type of construction that would not have been subject to collapse if neglected for 30 years in a corrosive chloride deicing environment? I don't, and I have specialized in parking garages for 30 years.

Don't get me wrong, I have always argued that a cast-in-place system with a good waterproofing membrane system protection is a superior system, even though there are costs to installing and maintaining the membrane.

In fact I had a battle with the architect for a 9300 car garage a number of years ago...the architect insisted that it had to be a double tee garage with caulked joints. I was against it for the reason that in a garage that size they would be repairing the joints almost continuously...although they had another precast double tee garage at the same site that was about 20 years old and reportedly had been doing well. The owner of the garage wisely decided to listen to me rather than the architect so I won that battle (the architect never forgave me) and today there is a beautiful 9300 car cast-in-place garage there.

RE: Topping Bond Strength on Precast Double tees

This is pretty timely for me as I'm also working on a one story parking structure in Canada. Thanks for blazing the trail ajk! I think that we want two important things from our topping:

1) Durability. I've read that the topping should be at least 4-5 ksi to match the likely durability characteristics of the double TEE's. Obviously, resistance to delamination is big too, hence the pull-off tests.

2) Longitudinal shear capacity (Agent's point). Do pull-off tests correlate to longitudinal shear capacities somehow? They must. I'd like to know more about that if anyone is well versed on the issue.

In my region, it now common to use pre-topped double Tees. This seems like a much better way to go from both a strength and a durability standpoint. Without any reinforcing in the CIP topped system, I'm surprised that the Tee flanges area able to resist code specified point loads. Your effective d wouldn't be more than an inch or two. In my parking structure research, I came across a company that markets FRP reinforcing for the flange toppings. Clever.

I'm using hollow core plank with topping for some areas of my structure. How come you avoid that system?



The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

RE: Topping Bond Strength on Precast Double tees

(OP)
Kootk - where in Canada is the garage to be? what is it to serve - a shopping mall, or an office building or a hospital or other?

- Do you live in Canada? If you don't you will need to get CSA Standard S413 "Parking Structures" immediately. If you live in Canada, you will liklely already have it. Read it cover to cover. Not only is S413 mandatory in every province of Canada, it has a wealth of very practical infomation in its annexes, which you would be hard pressed to find in any other single document.

- I did not say the flange has no reinforcemnt. It does have mesh. However unless you are an engineer working for a precaster, you need not concern yourself about the design of the tee and the topping. There are precasters who have very specialized knowledge about precast double tee garages and they have developed specialized details over the last 30 years. As well they know how to design and reinforce for concentrated loads, etc. The usual practice os for the consulting engineer to design the foundations, and write a performance spec for the precats and the precaster's engineer deigns all the precats elements and cast-in-place topping and any required reinforcing in the topping.

- As for the pre-topped unit, I have not used it, do not use it, and never will, for a lot of reasons. In the Toronto area, I don't know of any so-called pre-topped tee (I call them untopped tees).

- I also would not use hollow core. If anyone does design it, my recommendation would be to put a reinforced waterproofing membrane on top and overlaid with 2.5" minimum (perhaps 3") of compacted asphalt wearing surface. There are numbe rof waterproofign detials that you must show on your drawings.

- If this is the first garage that you have ever designed in Canada, I would recommend that you hook up with a structural engineer experienced in parking garage design in Canada. The Canadian regulations are significantly more stringent than American.

- A lot of people who have neve designed a parking structure think that there is nothing much to them. Actually they are amongst the more complex buildings and require experience and specialized knowledge to design properly.



RE: Topping Bond Strength on Precast Double tees

@ajk:

- I practice in Canada presently.
- the structure will serve a medical clinic in Alberta.
- this is indeed my first stand alone outdoor parking structure.

I agree, parking structures are pretty specialized. It's been fun to learn about them. Going to the mall and the airport are entirely different experiences now. Instead of seeing dead people, I see durability details...

I've digested S413, the Chrest book, PCI's offerings, product literature from a few local precasters, and all the random goodness available on google. I should be able to conjure up a parking structure through sheer application of will now. I've also been in close contact with LaFarge's precast group and a precast specialist that works for my firm out east.

However, it sounds as though you might be the guy that I need to talk to. Can you tell me why you're so skeptical of pre-topped double tees and hollow core?

Pretopped tees are purportedly more durable, attractive, stronger, and more economical than site topped tees. They even can be made with a great mechanically raked traction surface. I reviewed several pretopped parking structures in the field. They look great. As far as I can see the only disadvantages are diaphragm strength and more potential water leakage paths. The diaphragms strength is easily resolved with connection hardware and water leakage can be addressed through sealant maintenance. If the precasters themselves are to be believed, pretopped tees are "the future".

As for the site topped hollow core, how is that fundamentally any different from site topped tees from a waterproofing standpoint?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

RE: Topping Bond Strength on Precast Double tees

This was the article that got me worried about the concentrated loads: Link.

I've also read that it's common practice to consider any flange point load as shared with the flange of the neighbouring tee. While I'm sure that's reasonable, it seems a bit liberal to me. Not all tee flanges even have neighbours.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

RE: Topping Bond Strength on Precast Double tees

(OP)
- Looks like you have indeed done your homework. Yes those are all the references that I would have recommended. The Chrest book is excellent, but it describes American practice which is much less stringent than Canadian as prescribed in CSA S413. If you have been talking to Conforce, my understanding is that they are an excellent precaster and should be very knowledgeable about parking garages. I am from Toronto, so I have no direct experience with them.

Untopped (Pretopped) Tees
- I don't like untopped (or if you buy into their PR, "pretopped"). If however, you have been to see a couple of them, and you have found that they are performing well over say a 20 year period, with no signs of previous extensive concrete repairs, and you also think they look great, then you would be justified in going for it. Places to look for deterioration are i) the ledge of the inverted T beam that supports the double tees, ii) column corbels, supporting stairs well walls and the like, iii)the soffit of the stems of the tees, and iv) expansion joints. All these locations are subject to reinforcement corrosion due to leakage and concrete spalling. Item i)can be particlarly common and difficult to repair properly. Item iii) is virtually impossible to repair and has required demolition of at least one 30 year old garage in Toronto within the last coupel of years.

The following are my reasons for not using it.

a) they have thicker slab (I believe it is 100 mm slab) and so cannot be warped as much to provide the required drainage slope;
b) the adjacent units cannot provide a perfectly aligned top surgace the way a cast-in-place topping can, and so in my opinion do not look as good, and perhaps you might feel it a bit when drive over it;
c) they are only rarely used in the Toronto area which is my main area of practice; I know of only one that is untopped and that was built a long time ago. I went to see it about 20 years ago and did not find that it looked as good as c.i.p topping garages;
d) they may be more prone to leakage, which is the Achilles heal of the precast systems;
e) they are heavier than untopped tees so fewer can be transported by truck and transporation cost goes up (but that does not affect durability, but is just something to keep in mind).

I have never ever heard of any problems with concentrated loads on double tees, so I think the experienced parkign garage precasters know how to design for that. Perhaps some of the design is based on load testing. The precast and topping is generally designed by the precaster, but I would insist on a precaster who has proven long term (at least 20 years) experience on parking structure design. You have that in the Calgary area which is at least as sophisticated if not more so than Toronto. There used to be someone (I cannot recall his name; he is no longer with Conforce) from Conforce who was on the CSA S413 technical Committee with me.

As for hollow core, I would not use it because:

a) it is only 1.2 m wide so there are two to three times as many joints to leak as with the double tee system!;
b) doubtful that uniform bearing can be achieved on the suppoorting beam over the full 1.2 m width of the precast unit; would that cause rocking of the panel?;
c) if water gets into the cores and freezes, what then?
d) they may be relatively flexible (compared to double tees) and I have heard that this may cause some breakdown of the joints between units;

I know of only one garage (for a medical centre) of hollow core in Toronto, perhaps 10 years old, but there could be more, I don't know. It has a waterproofing membrane and several inches of asphalt over it. It still leaks but is in generally decent condition except for signs of minor scaling at the soffit adjacent to all supports...later I will see if I can find some pictures and send to you. Also one location where the leakage has caused severe corrosion of supporting steel. If I did ever use hollow core, I would insist on a rugged waterproofing system over it, with the membrane reinforced over all joints.

Have you been to see any hollow core slab garages and how they are performing?


By the way, there is a new edition of S413 that is to be published I believe later this year but there are no really major changes, except we have deleted the statement that said only alternate joints in hollow core system need be tooled and sealed!.

I have to run to an appointment so I have not had time to proof read the above...likely lots of typos. Sorry. Hope the above helps a bit.



RE: Topping Bond Strength on Precast Double tees

...and prior to adding the topping the surface of the DT's should be saturated surface dry/damp.

Dik

RE: Topping Bond Strength on Precast Double tees

Right on!

RE: Topping Bond Strength on Precast Double tees

That helps a TON AJK. Thanks for taking the time to share all that with me. My tender drawings go out on Monday. I wish I could fly you out here for a concept review somehow. You've earned a beer or four.

For my project, the hollow core is being used for a ramp structure rather than the main parkade. Still, the same concerns should apply. In particular, I think that water in the hollow core is a serious concern. I'll detail the planks with end grouted cores to try to mitigate that.

I gather that your primary objection to pretopped tees boils down to this: Pretopped = more sealant joints = more water leakage = more durability issues. As I understand it, the system hasn't been prevalent until pretty recently in Calgary. All of the structures that I toured were built within the last five years and so I can't personally vouch for the long term performance.

I did my tour of a year old parkade on a rainy day as it were. While taking a picture of a vector connector from beneath the roof deck, a big droplet of salty water fell down from the ceiling right into my eyeball. It was quite unpleasant and altogether consistent with your appraisal of things.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

RE: Topping Bond Strength on Precast Double tees

(OP)
Thank you for the very kind words. Good luck with your project.

As far as pretopped being the wave of the future, I have a hard time believing that because they are nothing new...been around for at least 30 years I would say, and they certainly have not caught on in this area. Perhaps the costs and economies of the different systems are differnt in various parts of the country, or maybe the different precast manufaturers have different preferences.

How many stalls will this garage have, and how many stories?
Is it all above grade?

RE: Topping Bond Strength on Precast Double tees

Durability of the structure is not the only concern about leakage. I know of post-tensioned, cast in place carparking structures here in Australia where the issue has been leakage onto the automobiles below. And of course, where parking is over commercial or residential space, that is arguably worse.

RE: Topping Bond Strength on Precast Double tees

(OP)
CSA S413 requires a waterproofing membrane over all cast-in-place post tensioned systems with unbonded tendons. For cast-in-place concrete, only bonded tendon systems allow omission of the waterproofing membrane if the designer so chooses. I would hope no one is so unwise as to build a garage over occupied space, irrespective of the structural system, without a waterproofing membrane. If any engineer thinks that post-tensioning can prevent all leakage, he is unwise, to put it gently.

CSA S413 states in the first paragarph that one must protect against both corrosion AND leakage.

If you are interested in garage design for durability, CSA S413 is the best thing to read up on.

RE: Topping Bond Strength on Precast Double tees

CODE --> ajk1

For cast-in-place concrete, only bonded tendon systems allow omission of the waterproofing membrane if the designer so chooses. I would hope no one is so unwise as to build a garage over occupied space, irrespective of the structural system, without a waterproofing membrane. If any engineer thinks that post-tensioning can prevent all leakage, he is unwise, to put it gently. 

In Australia, it is common practice to have bonded PT roof level framing systems (incl. parking decks) over occupied spaces with decades of success in terms of durability and serviceability, withOUT waterproof membranes.

Local construction practices avoid construction joints, opting for large pour areas. High strength concrete using shrinkage compensating cement are common.

Design and detailing includes min P/A of 2 MPa (300 psi), continuous top reinf in both directions, 35mm+ top cover, and details that minimize restraint.

RE: Topping Bond Strength on Precast Double tees

I should more correctly state that "shrinkage-limited" cement not technically shrinkage-compensated cement is used.

25% initial stressing at 24 hours is also used, along with high-early strength concrete.

RE: Topping Bond Strength on Precast Double tees

(OP)
How much corrosive deicing salts do they use in the winter in Australia? That cover would be totally inadequate here!

Interseting that in Australia you have succeeded in making it watertight without a membrane, with no failures.

RE: Topping Bond Strength on Precast Double tees

ajk1,

I used to work in Toronto (2 years in late 80', early 90's) with a consulting structural engineering firm, and your weather and environment is like a real-world testing lab. Did they ever pull down the Gardner Expressway!

No de-icing salt used in Australia.

Our chlorides come in the form of "coastal chlorides" and our codes stipulate the exposure classification based upon proximity to the body of salt water, and min cover is determined from the grade of concrete used, with a min grade specified for each exposure classification.

There are some failures. The main objection to waterproof membrane is that they are tough to maintain and they cost a lot install and replace.

RE: Topping Bond Strength on Precast Double tees

I agree with ajk1 that concrete roofs, floors or whatever, over occupied spaces should have a membrane. But when it is done carefully, with enough crack control reinforcement, and with attention to detail as to restraint, they work most of the time without membranes. We don't use unbonded PT in Australia.

RE: Topping Bond Strength on Precast Double tees

(OP)
I wonder if in Australia you have the seasonal temperature swings we have in most of Canada and the northern U.S. i.e. in Toronto from minus 20 C to plus 35 C, and greater in places like Calgary. That produces significant stresses that low shrinkage concrete does not address. Perhaps that is why you can do some things in Australia that we cannot safely do in most of Canada. When I was in Sydney 6 years ago I some things with masonry construction that absolutely astounded me...it would never work here because of the freeze thaw cycles.

It also depends what is in the occupied space - if it expensive electrical equipment, or say clothing store, etc., leakage could do a lot of costly damage. Have you ever been to Canada during our winter - your summer?

RE: Topping Bond Strength on Precast Double tees

You are right...Australian climate conditions are much less severe than in Canada. Most of the population here is in cities close to the coast, and we complain about the cold when it gets down to 10C (50F), although we have had a few cool 4C mornings lately in Brisbane. In some of the inland centres such as Canberra, it goes below freezing, but nothing like your winters.

I know about cold winters, having been born and raised in Virginia, but have spent no winters farther north than New Jersey. But Blacksburg, VA can be cold. -15F, with 40MPH wind, caused classes to be cancelled one day in 1963.

RE: Topping Bond Strength on Precast Double tees

hokie and ajk:

I've done a lot of research on Elliot Lake collapse... and the problem was the system used. The HC was overspanned and the topping was never used properly... It was an architectural error that an engineer 'walked' into. He was correct in stipulating the loads... only the system chosen could never have worked and there were problems almost from day one.

As far as using HC slabs... there's a parkade in Winnipeg that I did about 35 years or more ago that is still up and running... using 12" HC with a topping... and proper jointing system.

Dik

RE: Topping Bond Strength on Precast Double tees

But dik, notwithstanding the inadequacy of strength at Elliot Lake, the system sounded very similar to what is being discussed here...precast, bonded topping, and reliance on sealant joints. The joints leaked profusely, and in this case the supporting structure for the precast was structural steel, which failed due to corrosion. Correct?

RE: Topping Bond Strength on Precast Double tees

Yup... but, the original system would not likely have worked... the HC was overspanned, and the engineer had no concept of the strength of the system selected by the architect. The topping was just poured on top without regard to shrinkage, etc. 200' or so or topping without any control joints... to crack at random with no consideration of a waterproof membrane... a recipe for failure... failure occured by corrosion of the structural steel that was missed by numerous top quality consultants many of which I have provided consulting services to, resulting in a fatal collapse...

Dik

RE: Topping Bond Strength on Precast Double tees

Maybe they were "top quality consultants", but in this case their work was not of top quality.

RE: Topping Bond Strength on Precast Double tees

agreed, but there is no indication what the scope of their work was...

Dik

RE: Topping Bond Strength on Precast Double tees

I think that is a copout. We all know that many architects are incompetent, but engineers should accept being held to a higher standard of accountability. If an engineer cannot adequately define and complete a task, he should not accept the assignment.

RE: Topping Bond Strength on Precast Double tees

agreed hokie... but other than scope, I cannot explain why it was missed... I worked for the one for a decade and they were right up with reinforced concrete, parking garage design and corrosion issues... one of the better firms in Canada... I've done consulting work for two of the others and they were well versed in deterioration... and Ron can speak for Trow... another bright light... Other than scope, I cannot explain why this was missed.

Dik

RE: Topping Bond Strength on Precast Double tees

Maybe it was a bit far to drive from their main offices, and they didn't send the people with the required experience? Just thinking, I don't know.

RE: Topping Bond Strength on Precast Double tees

Trow did a credible condition assessment in the early 90's and made recommendations for repairing the leaks then as well. Not sure if anything was done per their recommendations. Their opinion of cost for the repairs at that time was over 1.2 million CDN.

Trow was/is a high quality group (now exp consultants). Not sure of their exposure in this one.

RE: Topping Bond Strength on Precast Double tees

Sometimes it feels good to be retired.

BA

RE: Topping Bond Strength on Precast Double tees

BA...You are a smart man!!

RE: Topping Bond Strength on Precast Double tees

Hi dik - where exactly did you read that the hollow core was over-spanned? I cannot recall reading that in the reports.

RE: Topping Bond Strength on Precast Double tees

Hokie... haven't forgotten, just so busy... will try to reply later today.

Dik

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources