huangyhg

coring through concrete beam
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.
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
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.

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
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.
asixth,
you should be able to locate the stirrups with a cover meter.
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
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...
sorry, but i don't. of all places though, i bought it at ace hardware.
mike mccann
mmc engineering
ys / mike,
were the videoscanners bought by your company or did you purchase one for your own personal use?
asixth,
a cover meter should be standard equipment in a structural engineering office.

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