Concrete Plinth Design

[PST09]

Firstly can i say what an excellent site. There is so much usefull information on here, and so many people with a wealth of knowledge!

Basically my problem is that i have designed a concrete plinth to support a filter system (designed considering Fx, Fy and Fz) but this plinth needs to be on cast onto existing concrete.

Im planning on using dowel bars drilled and epoxey fixed into the existing concrete. I assume shear is going to be the main component acting at the interface between the old concrete and the new, but dont know how to calculate the minimum embeded length, diameter, or spacing of the dowel bars?

Can anyone offer any guidance/equations or refrence material that my be of assistance.

Many thanks in advance.

 

[oneintheeye]

do a search for concrete society report 34. Its UK (eurocode based) primarily but the dowel design is 'basic' calculation of lengths etc and will be the same analysis wherever you are.
The embedment length is only effective over a certain length without further detailed checks. Think its uses 8*diameter as a max. Dowels will only transfer load within a certain distance form the load applied so dont simply space them out equally over a vast area to cater for a localised load transfer.

 

[PST09]

herewegothen, many thanks for your post.

Im having trouble finding a link to the report that you mention. Im not a member of the Concrete Soceity which seems like the only place you can get it from. Do you have a link to it ?

For the dowel bar spacing beneath the plinth with axial loading im assuming there is a zone of influence beneath the plinth in which the dowel bars will be placed, any bars outside of this area will not provid any additional load transfer?

 

[oneintheeye]

what are you asking the dowels to do? Resist shear to keep the plinth in place? Make the plinth and slab act as one slab?

 

[PST09]

Yes resist shear and hold the plinth in place

 

[oneintheeye]

You need to check shear capacity of the bar, bending capacity under the shear load from above and also the dowel punching out of concrete.

 

[PST09]

Many thanks.