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Demolition of Composite Floor Slab

Demolition of Composite Floor Slab

Demolition of Composite Floor Slab

(OP)
I am working on a demolition and replacement of a concrete slab w/deck for a composite floor system. We are essentially removing the concrete slab along with the deck and all the shear studs.
We will be shoring and reusing the steel beams which will be installed with new studs and new concrete slab w/deck. The largest bays contain 40 foot long girders with beams spaced at 8' o.c.

Some of the concerns that I wanted to discuss with the community are:

1. Pneumatic breakers/Jack hammers are proposed to be used for the demolition of the slab. How would the vibration caused by these effect the steel framing and the connections? As per the cut sheet the lowest vibration level for one of these machines is 6.2 m/s2 with a weight of 96 lbs.

2. If Jackhammers are not recommended for demolition of composite floor system, then what is the best way for demolition without adversely affecting the structural integrity of the steel framing systems.

3. Any suggestions for the demolition analysis of the existing steel framing system?

I have been researching on these topics and have not found much information discussing these issues. I hope this post can lead to some useful contributions for a better understanding of demolition of composite floor systems. Please include any/all useful information from experience or from any publications that you might have come across.

Thank you.

RE: Demolition of Composite Floor Slab

I've never used it, but "hydrodemolition" is effective in removing concrete without vibration: Hydrodemolition

As a bridge contractor in the 1970's we used pneumatic tools to remove portions of bridge decks to allow widening of the roadway. Some of the existing bridges had steel beam supported superstructure. Bridge widening has been preformed this way for a long, long time. Did not encounter, or hear of any problems with vibration damaging the steel to be reused. However, both the large mass and substantial structural bracing of a bridge is likely to make it more resistant to vibration damage than a building.

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RE: Demolition of Composite Floor Slab

For bridges, my company directs the use of large excavator mounted hydraulic hammers all the time. But as SRE points out, bridge stringers may be more substantial than the steel framing you're talking about. Make sure to do a sanity check based on web and flange thicknesses.

With a relatively experienced demolition subcontractor and a properly sized hammer, you shouldn't have problems with hammering the deck off. Sometimes an inexperienced operator will get aggressive and bend up the flanges. Depending on the composite connectors, you may have to make a pass with heavier equipment to break out most of the deck and then go back with a lighter touch to clean out the embedded portions.

#3 is a little vague. What aspects of demolition analysis were you hoping to understand better?

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