Bell Tower

[scrolljoe]

We are attempting to make a free standing bell tower for our little rural church of 20 parishioners . An old timer came up with the idea to cast a base a about 5 feet square x 10 inches thick- use a single galvanized pipe in the center [ instead of rebar] of a 20 foot round column whose mold is a 8 inch PVC diameter pipe, 7 feet long. The intention is cast the concrete in the PVC pipe then slip it up 3 more times over a number of days to achieve the 20 foot height. At the top , the old bell- cast in 1835 and weighing 150 pounds- will be perched between 2 short concrete columns 2 feet high.

Over the last 40 years the wooden bell tower had to be changed twice because of termites and general rotting. Hopefully putting same in concrete will outlast the ” ole 6 “as we call ourselves in the church. There is no shortage of ideas or hands to do “Self Help” but we need some technical “know How.” The average weight of the 8 inch column and bell is 1800 pounds and the base 3150 pounds. Is the base an overkill and if so what dimensions do you recommend ? The soil is somewhat clay. Thanks for any advice.

 

[MotorCity]

Here is my advice:

1. Post a sketch of what you are trying to build

2. Using galvanized pipe instead of rebar is a terrible idea. (Using only one bar is also a bad idea).

3. The concrete will bond to the PVC pipe and you will never be able to get it off without breaking it to reuse it as "formwork".

4. 8" columns are too small. Any columns 20' high will need steel reinforcement.

4. Hire a structural engineer. This is not a DIY project.

 

[msquared48]

I agree. Hire a local SE. If you don't, the bell might end up ringing on the ground.

Mike McCann, PE, SE (WA)

 

[JAE]

Get a licensed engineer....perhaps not your old timer.
(I'm older as well so this isn't age discrimination)

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[Ron]

Not sure how old "Motorcity" is, but I know how old Mike is and how old JAE is.....I also have it on good authority (from both Mike and JAE) that I'm reasonably old as well, so again, no age discrimination here, just a bunch of years of structural engineering.....get a local structural engineer involved.

 

[JAE]

...but Eng-Tips never gets old.

and old engineers never die - they just change their plans....yak yak yak.


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[scrolljoe]

G'day Guys!

Your comments are noted and well received.

Firstly I want you to address your mind to the fact that all that stands on this 8 inch concrete column is a bell weighing 150 pounds.

Secondly: The usage of PVC pipes as a concrete form is an age old tested method ; all that is done is that it is cut down the middle ,oiled and retied. The concrete is then poured within. After a few days the ties are removed , a chisel inserted in the cut to expand the pipe and it is pushed up and retied for further casting.

Thirdly :The reason for using a single 3/4 galvanized pipe instead of rebar is because the dead weight above is a mere 150 pounds. At one point we even considered using a single 1 1/2" pipe but the agreed on the smaller 3/4" .In relation to our collective skills to bring this to fruition is a done deal; where we are divided is the size of the slab / base on which the column sits. We call ourselves the Five Septu's as we are all over 70 .Thanks for your continued input and do enjoy what's left of the weekend.

 

[JAE]

scrolljoe,
The height of 20 ft. is very high for an 8" diameter concrete column.

With typical wind loads you would have up to approaching 20,000 ft-lbs. of factored wind moment at the base of the column along with perhaps 2000 to 2400 lbs. of axial force (factored).

A non-reinforced concrete column cannot deal with that so you need to utilize reinforcement in the column along with circular column ties. All of this doesn't include second order effects from the pole bending laterally. The footing size (your original question) depends on the soils.

Above many of us have suggested getting an engineer to get you a design for this - not a big effort certainly - but you'd have some assurance that it is designed correctly to give you a good tower that will last.

The issue of jump-forming the column may be doable but your suggested design is very questionable.

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[Ron]

Agree COMPLETELY with JAE's last comment. You seem to be hell-bent on doing what you want to do and just want someone to bless it. What you are planning to do will likely hold your bell as long as all stays vertical and you have no lateral loads. That's not practical and you will have lateral loading. If you want to ignore the given advice go ahead....foolish. I hope that none of you 70-years olds are standing next to the column when the wind blows.