Grade Beam

[boricuastructural]

I have to desgin an eccentric footing on the property line of my building. One of the suggestions for the design was to tie the footings together using a grade beam. Where does it tie them together? At the base of each columns? Or tying the foundations together at he base of each foundation?

 

[hokie66]

This is called a combined footing. You tie the external footing to an internal footing by way of a beam which takes the bending moment created by the eccentricity. Position can vary, but usually the top of tie beam is level with top of column footings.

 

[boricuastructural]

Thats when you have two footings. I have a series of columns lets say in the x dir and the property line is on the y dir. I dont have a column on the y dir to tie the columns in a combined footing. Thats why I have been advised to tie the columns together in the x dir.

 

[yasser123]

Dear hokie66
Combiend footing is 2 column footing in the middel of a building, while 2 footings with grade beam should be used at property line

 

[msquared48]

How far is the bottom of the footing below finished grade at the property line? My thought is that if the stem wall / basement wall is high enough, that might be able to be designed to serve as the grade beam as it is probably much stiffer, if it is deep, than the strip footing beneath it.

Further thought - I assume from your post that you were able to success fully design the eccentric footing without overstressing the soil. Correct?

Mike McCann
McCann Engineering

 

[csd72]

The grade beam takes the eccentric moment and counteracts it by cantilever action. If you do not have a second footing in the correct place then you may be able to just use a masss of concrete at the end of the grade beam to take the moment out. You may also be able to use some of the slab to help.

You may also need hairpins at the slab level to resist the column spread (if this is a portal framed building).

csd