×
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

Coring through concrete beam

Coring through concrete beam

Coring through concrete beam

(OP)
Hi guys,

I have a situation where an existing 600 x 190 beam (24" x 8") needs to be cored so services can pass through. My thoughts are that I should try to do this in a low shear region because the beam is not going to be scanned to determine the location of the shear ligs.

And I should core approximatley within the middle third of the depth, this way I will avoid any tensile steel and the compressive stress block should not be affected depending on the depth of the neutral axis.

What do others think of this logic.

RE: Coring through concrete beam

Best place is at NA of the beam near mid span where there is a low shear area and you are likely away from reinforcing.  Use a Hilti meter or similar to check for rebar locations.  Be careful and if possible run this by the EOR.

Dik

RE: Coring through concrete beam

They should try and find the ligs using a stud finder or similar, this often works.

Otherwise, the use of a regular percussion drill for the outer 50mm would minimise the chances of coring through reo. Percussion drills dont tend to cut reo.

As per your question, yes I would think it reasonable to located the hole in the middle third, in the middle third of the beams span.

 

RE: Coring through concrete beam

If this beam is a transfer beam, be careful of the shears as the pattern will be different than for a uniformly loaded beam.  In this case, if there is no EOR available, I would try to figure out the shear pattern, then test, mark and drill.

Mike McCann
MMC Engineering

RE: Coring through concrete beam

(OP)
What is the cheapest method to accuraltey determine the location of the reinforcement. They recently had an x-ray out there to scan the slab and it cost them $4,000AU ($3,000US). They do not want to go down this path again, and going by dik's response above I really should make some attempt to locate the shear lig.

RE: Coring through concrete beam

asixth,

You should be able to locate the stirrups with a cover meter.

RE: Coring through concrete beam

I have used a Zircon Videoscanner 5.0 for years on tilt-up walls.  Won't tell you the size, but does locate well.  Handheld.  I've had it for 10 to 15 years now.

Mike McCann
MMC Engineering

RE: Coring through concrete beam

I've had some success with stud meters in the past as well...

Hey Mike; Great tip! Love it when someone includes the precise product name.  My Zircon is the little black jobby without a screen; Do you happen to know if the new Videoscanner (5.5 is the currently available model) works as well as your 5.0?  Just worried they might have reduced the strength, or improved the software for timber which might have limited the general application.  Thought I'd ask on the off chance you know...

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

RE: Coring through concrete beam

Sorry, but I don't.  Of all places though, I bought it at Ace Hardware.

Mike McCann
MMC Engineering

RE: Coring through concrete beam

(OP)
YS / Mike,

Were the videoscanners bought by your company or did you purchase one for your own personal use?

RE: Coring through concrete beam

asixth,

A cover meter should be standard equipment in a structural engineering office.

RE: Coring through concrete beam

(OP)
Hokie,

Thanks mate, I put it to my company today to purchase a cover meter but they didn't like the idea. So I think I might have to buy a cover meter myself. I might go down the hardware store and see if they sell any down there.

BTW, I have attached a picture of the beam that they want to core through, I have done some numbers on the beam and it looks like it is in a low-shear zone however, I want to try and avoid the shear ligs if possible.

RE: Coring through concrete beam

asixth,

I wouldnt go out and buy one yourself as they are not cheap, and it is really up to the contractor to do. These can be hired if necessary.

The 'beam' that you show on the picture looks like a ventilation duct to me. There is no chamfer in the corner and on the right hand side appears to be a few creases in the metal. Also it looks nothing like the beam beyond it.

RE: Coring through concrete beam

Does look like ductwork.  From the picture, it is hard to pick out the concrete beam.  I am sure apsix knows a beam when he sees one, but coring the ductwork should be dead easy.

RE: Coring through concrete beam

I do, and I'm sure asixth also does :)

RE: Coring through concrete beam

Asixth - if it is in a low shear zone, it might be easier just to determine if the ligs are even needed (V*<0.5 phiVuc). If not, you don't have to worry about locating the ligs.  

RE: Coring through concrete beam

apsix,

Sorry, must have been a senior moment.  I get you x-guys confused.

RE: Coring through concrete beam

(OP)
There is an existing duct going through the beam I want to core through, this penetration was considered during the original design in 1975.

The beam the duct passes through is 600 x 290, the transverse beams that frame through this beam are 450 x 190 at 1450 c/c, and they span to beams that are 900 x 290 and are at 8500 c/c.

Slab over is 100 deep.

This wasn't the best picture to psot so I will post another.
 

RE: Coring through concrete beam

So its the one with the metal trim along the bottom that you are framing into.

Steer clear of the edge of the duct penetration as this will have extra shear reinf either end. Also there will be an extra row of horizontal bears at the top and bot of that penetration that you need to miss.

RE: Coring through concrete beam

asixth,

Based on your photograph, I would guess that the section of concrete you are planning to core through is not a beam at all, but just a dropped soffit to receive the head for a movable partition.  I think the joists at 1450 centres span the 8500 between the 900 deep beams.

RE: Coring through concrete beam

(OP)
hokie,

Maybe, it appears like what you have described when looking over the existing structural drawings, that the 450 deep beams span to the 900 deep beams with then span onto the columns.

I will post the drawings on tuesday when I get back to work.  

RE: Coring through concrete beam

It looks like the concrete through which the duct penetrates, the same one you are looking to core, is a diaphragm brace for the beams.  Is there a load path which indicates load is going into this member, or out of this member?

It sounds like someone needs to review the plan to determine  the function of the member.  With a hole the size of the duct, I doubt there is any flexural load on this member.

RE: Coring through concrete beam

low shear, tension zone.

RE: Coring through concrete beam

(OP)
thanks to all those for their contributions so far. I have attached the structural drawings. The beam I want to core through runs transversly between B10 and B12. It hasn't got the size marked on plan but it is a 600 x 290 (24" x 12") with two significant penetrations that I assume will have been designed for. The beam hasn't been marked on plan or shown on elevations so I am hoping it is a soffit downturn to pick up the partition.

I ran a quick model to determine what magnitude of forces are going through that member and there is significant positive moment due to the curvature of the floor system. Saying that, the shear isn't of significant magnitude.

I don't think there should be a problem with coring through this beam provided I stay away from the tension steel and the neutral axis. And I have the slab x-rayed to map the exact locations of the steel.

RE: Coring through concrete beam

It is just a distribution rib, really just there for architectural reasons.  Although it may be picking up some load due to geometry, it would not have been designed that way, and I would not hesitate to cut through it.

RE: Coring through concrete beam

Maybe you can locate it on the HVAC/Piping drawings.

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