New Point Load on Exist Precast Planks

[peinma]

An existing building (built in 1950's) is framed with structural steel with the deck consists of 8" deep by 16" wide Flexicore planks with 2" topping. On the existing drawings the LL is either 100 or 200 psf. There is a plank schedule. An example from the scedule is plank mark followed by width and depth type (e.g. "W111 230psf Super with Stirrups") and negative steel (sq. in.). Looks like the psf number in the type corresponds to the superimposed LL (130 psf are in the 100psf LL area and the 230 psf are in the 200 psf LL area). Unfortunately there is no information on the prestressing or shear reinforcing. What's the best approach to analyze the planks? Should I back into the amount of prestressing and shear reinforcing by designing the plank for 100 or 200 psf? Can I use the point load distribution outlined in the PCI manual?

 

[BAretired]

You cannot analyze the planks if you do not know the amount of reinforcement.

How large is the new point load? Does it produce bending moments and shears much larger than that of the uniform load? If so, you are treading on thin ice.

BA

 

[paddingtongreen]

Back then, the wire sizes were changed to provide the design capacity, yours are 230psf and 130psf Superimposed Load capacities. Obviously, 30psf is allowed for the topping. Consider that your planks have the bare moment and shear capacity to support those loads, according to version of the code in place back then.

I would be tempted, if permitted, to see if the point load displaced enough of the LL to not increase the moment or shear to more than the original loads.


Michael.
Timing has a lot to do with the outcome of a rain dance.