Formwork

[Zaman01760]

what is the Procedure for shoring & re-shoring system of multi-storied concrete building

 

[CANPRO]

I don't think you're going to get the response you want on this. You need more than just advice from this forum - you will get help on specific questions here but not a general procedure. I suggest purchasing "Formwork for Concrete" by M.K. Hurd. Great reference. If you spend some time on google you will find some decent resources as well.

Shoring and re-shoring follow the same basic premise as any other design - you need to satisfy strength and serviceability conditions. It gets a bit more complicated for shoring/reshoring in that timing is critical because the concrete hasn't reached its design strength and you need to consider construction schedule.

 

[KootK]

You provide shoring for enough stories below the one being cast such that the one being cast can be successfully supported. The shoring should remain long enough that the cast slab gains sufficient strength and stiffness. You'll be somewhat at odds with your contractor in that you'd prefer more shoring that stays in place longer and your contractor will want the opposite.

This paper contains some info: Link. I'd also recommend getting your hands on ACI 347.2.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Archie264]

And if it gets pulled too early:

https://en.wikipedia.org/wiki/Skyline_Towers_collapse

 

[Angre]

The way I see the basics of this solution can be explained by the following table:

Storey Load Capacity Shoring Remarks
10 100 0 100 Concrete is fluid no strength Use 100% support
9 200 100 100 66% of strength developed use 100% support
8 200 150 50 100% of strength developed use 50% support
7 150 150 0 100% of strength developed use 0% support

 

[RHTPE]

Zaman01760 - When you ask about Procedure are you referring to describing the physical act of installation, or the analysis necessary to determine what should be done, or both?

The "Procedure" depends on a number of factors:
[ul]
[li]Completed floor(s)' strength(s) at each stage of construction load application(s).[/li]
[li]Formwork & shoring system used.[/li]
[li]Number of floors of formwork equipment used.[/li]
[li]The building's structural system (e.g. flat plate, one-way or 2-way slab, beam & slabs, P/T, transfer floors or beams, etc.).[/li]
[li]Type & strength of posts used as reshores.[/li]
[li]Concrete placement procedure & sequence.[/li]
[/ul]

The applicable combination of the above factors for a specific structure then influences how one approaches the Reshoring (or Backshoring) analysis. Note carefully ACI's definitions for Reshores & Backshores.

Analysis is kind of a 4-D problem as time (the continuing strength gain) becomes the 4th 'D'.

ACI 347 recommends a "Simplified Approach" which can be found in ACI-347.2R-05. Link
I use a "translated" form of that method for my clients' structures, and have used it successfully for a few decades.

There really isn't one fits-all "Procedure" as the project-specific combination of the previously mentioned factors can dictate different methodology.

The over-riding concept: The applied construction load must be safely distributed (through the shores/reshores) to an appropriate combination of completed floors below at each stage of the construction cycle.


Ralph
Structures Consulting
Northeast USA