Extending Existing Footing

[opa123]

Hi all
we had a project under construction, after casting of some isolated footing we found that the footings does not meet the required length and width dimensions, so we took decision to increase footing dimension around 50 cm to 30 cm from each side,
Existing footings were constructed that it has only bottom bars in both directions (U shaped bars) footing thickness is 400 mm so we decided that the side cover will be removed and then the vertical side of U bars will be straight then new concrete will be casted using suitable additive materials for connection between old and new surface.

1- Is it ok to have a footing without bottom bars not bent vertically at the end?

2-should I use dowels between the two surfaces of concrete or chemical materials is enough?

3- Should I use dowels if I need to increase footing thickness?

 

[JedClampett]

1) Maximum stress in the bars for footings is under the load point. As such that's where it needs to be fully developed. Unless you have something unusual, you don't need to hook the bars at the edges of the footing.
2) I wouldn't trust chemical bonding agents to do anything. Use epoxied dowels.
3) I'm not sure I understand in what direction you want to thicken the footing (I assume at the top), but using dowels is the best method to assure the concrete acts monolithically.

 

[jike]

Here is an alternate idea that may or may not work but might be worth your consideration. Check the in place soil bearing capacity under or immediate adjacent to the footings. If it is large enough to support the required load without increasing the footing size then make sure the footing has adequate flexural and shear capacity.

 

[swmiami]

The straightened bottom bars will act as dowels. After chipping off concrete cover, the surface is rough enough to transfer shear. I wouldn't use additional dowels or bonding agent on the side surfaces.

 

[cantthinkofaname]

Can you talk to your geotechnical engineer, and let him know your predicament?. The actual soil bearing cappacity may be higher that what was in the geotech report.