Prefabricated Foundation (Advise Please)

Dear keith,

I am seeing on a daily basis an ongoing project for the installation of steet lighting along a highway. I am involved with the project.

The Contractor is excavating for the Poles and subsequently lowering about 80x80x120cm precasted foundation with anchor bolts.

The trailer can carry about 8-10 pieces at a time, and you need a crane to lower the foundation in place. You can calculate the productivity depending on the people that you have doing the job. This is site dependent.

Doing the Shuttering, Reinforcement, casting, insulation and insulation protection for the foundation at site would take at least 4 days cycle for each. While doing the same at a factory will take much less time.

A small calculation depending on the number of iterative pieces can provide you with the results that you want.

With kind regards,

Samer

Same experience here for similar application: pipe-rack
Only difference,
the trailer was equipped with a lifting arm.

Hi Keith

I once workd on a high rise block of flats where the entire parking basement was formed of pre-cast load bearing retaining wall - beams and slabs. The only insitu element was the ground slab.

The final installation was very quick but there was a long lead in period. So procurement would be 12 weeks before excavation.

There was also a 1 week post tensioning period before any upper storey works could start.

The big problem was the drains and services penetrations which had to be pre determined as we couldn’t drill any holes in the walls after post tensioning.

All in all the cost / time benefit was with the precast system but you have to get it absolutely right first time.

Best regards

Mike Testro

Hey Keith,

here are my answers to your questions.

-What is the on site time saving?

It is one of the very basic reason to precast foundations.
when precasting, we do not only mean precasted in a factory, instead it can also be done on the same work site but not on the very location.
e.g. you are working at a location which is very congested and there are a lot of work to be done. you have machinery operating in the are where a foundation(A) has been designed. so while that machine is working on some other job you can have that foundation(A) precasted even a few meters away from its location and wait for the machinery to make space so that you can place it in itsplace.

-How long is the preconstruction phase?
It can not be defined. differ from project to project.


-Cost info would also be useful if available?
well it will definately reduce the total cost of the project by saving time but that particular activity(precasting) can cost you more.


-Is site preparation more onerous?
to me its just that you have to be extra carefull and plan properly, not missing any aspect/activity.