Development length of short pedestals

[Weyvu]

I have very short pedestals (on-pave) . Some having height of only 6". Is the reduction for devolpment length applicable to the development of the rebars towards the pedestal?

For example, #5 rebar requires ld = is 14" but available ld is only 6" - 2.5" (concrete cover) = 3.5".

 

[r13]

Are you talking about curb? If you have reinforcement in the pavement, just bend the bars 90° with hook tail standing up. Or just provide U bar placed upside down. I wouldn't worry about development length, but suggest to use smaller bars in a closer spacing for ease of bending.

 

[dik]

Can you use #3?... not likely for strength... like an ACI S-4 bar bend with the hooks going into the pavement? You likely don't need to develop it... if so, can you use a closed stirrup?

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

-Dik

 

[rowingengineer]

can you have the bolts/anchors for the equipment/structure connecting the low substrate such that teh pedestal is only a capping?

 

[dik]

better yet... thanks re

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

-Dik

 

[Weyvu]

The scope of my work is just to provide the capacity of the pedestals given dimensions and reinforcing details. This are pedstals for misc. piping and equipment supports, btw.

I was just unsure if this type of pedestal is applicable for the reduction of development length as per ACI. As per your replies, I proceeded with the calculations considering only the capacity permitted by the reduced development length.

Interesting idea RE. But I wonder if that wouod be okay if there is significant moment load? Currently, my approach is to neglect the additional capacity provided by the anchor bolt connected to the pavement and only consider the strength of the rebar.

 

[rowingengineer]

Weyvu,
I would create a bolt cage either using bolts or use reo with the end threaded... I would weld these into a cage to form a column.

 

[dik]

a couple of ties and 4 headed anchor rods, too...

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

-Dik

 

[rowingengineer]

Dik, good point, pavement is probably not that thick so headed hd bar/reo would be best.

 

[dik]

even threaded rod with heavy hex head nuts...

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

-Dik

 

[KootK]

Interesting idea RE. But I wonder if that wouod be okay if there is significant moment load? Currently, my approach is to neglect the additional capacity provided by the anchor bolt connected to the pavement and only consider the strength of the rebar.

Frankly, rowingengineer's method is pretty much the only way to garner meaningful moment capacity out of a pedestal situation like this. The 6" pedestal winds up being little more than an oversized grout bed and you get your capacity by:

1) Utilizing your anchor bolts as pseudo reinforcing or;

2) Effectively lap splicing your anchor bolts to the reinforcing within the depth of supporting concrete mass (sure, include a couple of inches within the pedestal too).

As you rightly surmised in the beginning of this thread, the development length problem is a problem. You cannot prorate the bar development lengths lower than the minimums, which will govern in this situation, and still use reinforced concrete principles to determine your available capacity.