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How do i determine if T-beam is prestressed?

How do i determine if T-beam is prestressed?

How do i determine if T-beam is prestressed?

I always thought you would be able to see tension rods from the ends of the beam if it is prestressed, but i was told by a contractor that is not always the case.

There is an overhanging T-beam that we want to cut but someone pointed out it may be prestressed and not a good idea. I suppose the question is two-fold:
1 - how is this prestressed without a visible rod at the ends? The beams look precast, so i do not think there would be multiple pours to simply hide the rod
2 - if it could be prestressed without the rods at the end, how would i determine whether or not it is?

thank you in advanced

RE: How do i determine if T-beam is prestressed?

You could scan it and determine from the scans if there was any prestressing. That's fairly quick and inexpensive.

RE: How do i determine if T-beam is prestressed?

If it's a manufactured prestressed double tee, I think you can cut it without problems. I believe (someone help me here), the way they make them is to use a several hundred foot long casting bed, prestress against bulkheads and cut the double tees into useable pieces. So if they can cut them there, you can cut them.
This is different than a post tensioned member, where they tension in conduits and anchor the ends. I'd agree, you do not want to cut those.

RE: How do i determine if T-beam is prestressed?

Look for an upwards bend deflection when there is no live load applied.
Or place a known load and calculate the expected deflection assuming a reasonable area of steel and no prestress. See if the measured deflection agrees with the no prestressed assumption, or indicates a prestressed state.

RE: How do i determine if T-beam is prestressed?

Scanning it is the way to go... cooking backwards based on deflections may be a bit iffy... Even though they are cast in tensioning beds, they often drape/harp the tendons to provide particlar resistance.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?


RE: How do i determine if T-beam is prestressed?

A magnetic scan will not tell the difference between prestressing tendons and rebar. Be careful with that.

Radiography, if done properly, will allow you to tell if tendon or rebar.

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