New Column Dowels To Be Grouted Due To Wrong Layout????

[RASHEED]

Dear Seniors,

One of our running projects has layout problem in which columns are out of 10 inches from center line.We need to adjust it as we have to install steel shed above it.Now there are two options,either we have to dismantle the footings or we have to drill holes and grout new dowels with chemicals.Now the problem is that what should be the depth of drill and if we drill hole then hook (development length) can not be provided.

So please give me suggestions based on your experience.We are using 20 mm dowels and axial load is 146 kip.

 

Thanks! 

[WR1]

This is anchorage to concrete problem (i think, other please confirm) There are many industry post-installed anchors companies like Hilti which provide their own software to calculate these things. Check on Hilti website.

[RASHEED]

Rana Waseem bhai we grout anchor bolts in already existing concrete section for installation of steel structure but i was not sure about reinforcement steel whether code allows the grouting of new dowels of columns or not??? 

 

Thanks!

[Muneeb Badar]

The best option is Hilti. If there is steel shed then do not use normal drilling. As there will be severe lateral loading due to wind. Ask Hilti, they are costly, but they provide very good and reliable solution as in Lahore on all roof top towers, normally hilti solution is applied.

 

Thanks

[EngrUzair]

Rasheed,

If the only problem you are asking about is how to anchor the dowels, you may contact Hilti (as you have already been correctly advised by others) for necessary advice as well as execution of job.  It is not a new technique, and is being commonly used all over the world, in connection with strengthening and retrofit of concrete structures.  There is no harm in using it, provided it is designed and executed by a specialist firm (like the one mentioned above).

 

You should however be careful that by relocation of column, column footing will become a bit eccentric, and may require rechecking to see it remains sufficient for the new situation or not. 

 

However, if you need a bit detailed advice, you will have to share some more details regarding your structure and extent of problem, e.g.,

- What type of structure it is? All RCC or partially concrete and partially structural steel? in what proportions?

-Total number of storeys,

- upto which level work has completed?

- what is the actual bay spacing in both direction?

- how many columns are causing problem?

- What other options you are thinking of?

 

 

Regards

[UmarMakhzumi]

My 2 cents- Hilti is your best bet. But you need to pick the right anchor bolt out of their catalogue and tell them which one would work for you. When you are doing that, please make sure that you consider group effect factors, sustained load factors and everything that is written in the foot notes.  Also, recheck your base-plate once you have confirmed number of Hilti bolts required and their pattern. 

 

Thanks.

[RASHEED]

Uzair bhai ,

Actually this is one storey steel shed structure in Lahore column size is 15 x 15 inches,concrete used is 2500 psi and reinforcement steel is 20 mm diameter.Column spacing is 20 ft ,height of column is 6ft and axial load applied on column is 146 kip.

 

i am afraid of neglecting the hook (development length) at the bottom of column as we can insert only straight dowels.

 

Thanks!

[UmarMakhzumi]

Uzair bhai ,

Actually this is one storey steel shed structure in Lahore column size is 15 x 15 inches,concrete used is 2500 psi and reinforcement steel is 20 mm diameter.Column spacing is 20 ft ,height of column is 6ft and axial load applied on column is 146 kip.

 

i am afraid of neglecting the hook (development length) at the bottom of column as we can insert only straight dowels.

 

Thanks!

 

Even if you provide a straight bar, all you need to check is that your bar develops greater than 146 kips of axial load + tension due to moment. If you don't want to use Hilti, use epoxy, drill the bars, check the epoxy-steel ULS, Concrete Breakout of Dowel Group and finish your design. Why are you afraid of neglecting the hook. Design for what you provide. Period.

 

Thanks.

[RASHEED]

Thanks Umar Makhzumi bhai jan...