Welding Heat

[JohnRwals]

Hi!
We know well embed plates will expand and concrete sometimes cracks due to excessive welding heat.
Is there any method to check if welding heat will cause concrete spalling around the embed plates?
Based on this method, can I decide plate size in addition to stress/strength analysis to avoid spalling/crack
as wider plates can dissipate welding heat easily?

 

[r6155]

You need a Welding Procedure Specification.

 

[Insha]

Good question. The detail you provided is a common one. I've never seen or heard of concrete cracking developing around
the steel embed plate due to the steel plate expansion. I would guess that the heat in the plate dissipates by absorption into
the concrete preventing any expansion large enough to crack the concrete.
You could also calculate the steel to concrete bearing stress and checking that against the bearing stress capacity of the concrete.

 

[HTURKAK]

Based on this method, can I decide plate size in addition to stress/strength analysis to avoid spalling/crack
as wider plates can dissipate welding heat easily?

My opinion is NO!.
If the plate is embedded in concrete , during welding , thermal expansion of the plate can destroy the bond btw the concrete and the plate and induce spalling in the surrounding concrete.
You may consider some measurements to limit the temperature stresses; such as ;use small dia welding electrode , and use small welds with multiple phases ..

 

[r6155]

Good information in PIP STE05121 Anchor Bolt Design Guide.
PIP= Process Industry Practices

 

[Klitor]

I remeber a similar thread few years back.
I think it was not a problem. Try search function

Personaly I worked on a nuclear project with thousands of those. Dont recall there were issues

 

[dvd]

My thoughts on this, which I have pondered before but not executed -

CTE of concrete and steel are very similar, so plate expansion vs concrete expansion should match at an interface if the plate stays reasonably cool.

Method to get some general idea of how hot the plate would get based on plate mass and weld length:

If the OP has Blodgett books there are some nomographs for weld speed and deposition based on weld parameters. Otherwise, there are online calculators.

With weld speed, voltage, and current it is possible to get the heat input per unit length from online calculators (Hobart). Multiplying the heat input per length by the total weld length should give an idea of how much energy is transferred into the plate.

Energy stored in plate, Q =q = m x c x ΔT - do some algebra and get Tfinal = Q/ (m x c) + Tinitial.

Multiple simplifying assumptions apply.

 

[Flotsam7018]

Results will very much depend on the weldment and resulting heat input. For larger weldments a WPS will be key as @r6155 eludes to in order to keep interpass temperatures within an acceptable range, what that range is will be your job to determine.