Tilt Up Panels 1

[neillydavies]

We are now receiving many projects for designing light and heavy industrial units and many of the clients prefer the use of tilt up panels.

I would like to get a general consensus on the current practice in terms of average thickness, reinforcing and method of attachment of panels to structural members and use of the panels to support floor memebrs.

Neilly Davies Consulting Engineers

http://www.neillydavies.com.au

 

[haynewp]

There are some publications from the Tilt-Up Association that should be of a lot more assistance:

http://www.tilt-up.org/resources/literature.html

We used to use either 6" or 7 1/4" thick panels for big box stores (>20ft clear heights). The bars were, for example, #5 at 18. A lot of embed plates were used for the connecting joists and joist girders, and continuous angles welded to embeds for deck ledgers. They are pretty easy to design, in general.

 

[JAE]

We usually start with L/50 as an initial thickness guide - adjust from there depending on loading, wind/seismic loads, etc.

Usually use pockets with embedded plates for joints (formed with foam blocks attached to the embed plate which is supported with small steel tab legs and tied to rebar.

Embedded plates on the inside face also works - and is also used for attachment of continuous deck edge angles used for diaphragm chords.

Attachment to the base is by embedded plates or angles. One detail we've used involves an embedded angle set at 45 degrees (legs pointing down) where one side of the angle has anchor rod holes and forms a pocket with foam blocks and the other side of the angle has welded bar anchors developed up into the panel. The holes are for post-installed drilled-in anchor rods to the footing below. This detail may be patented so not sure it can be used.

 

[frv]

Tilt-up is very common in my part of the Country.

You should try to keep panel thicknesses to sawn lumber dimensions. This is to facilitate forming of the panels. 5 1/2" is commonly used on smaller projects, but may not be adequate for industrial facilities given that they often have large clear height requirements. 7 1/4 is used extensively.

Another thing; with 7 1/4" panels you can fit two mats of steel if you need to. It's a good idea to do so and provide closed ties at open panel legs with large openings.

Make sure you provide at least two bars around all openings extending the development length beyond the edge of the opening. Usually #4's or #5's.

You can use 3ksi concrete for the panels, but I've found that 4ksi concrete greatly increases the panel capacity.

Just a few pointers, but it would be good to read up on this. There are several publications dealing with this. Also, PCAWall is a FEM program you can use to check panels.

 

[mdavis1]

a few things here, L/50 is a good starting place for panel thicknesses, but I always keep the thickness to sawn lumber dimensions so panel forming is easier and quicker. the contractor can't really mess up panel thicknesses then. i usually start with 4ksi concrete and if need be go up to 5 ksi, anything over that gets to be expensive and economically not worth it. also if the panel have rustication on them, you have to adjust your calculation for a structural panel thickness.

for example: if a panel is 8" thick and there is 3/4" rustication, your total panel thickness is 8" and your structural thicknes is now 7.25"

and when looking at your D dimension for your rebar always take the lesser of the two values.

 

[escrowe]

Certainly the combination of tiltup wall and double-t roof
is popular in our hurricane zone and for some commercial/industrial applications.

From a construction standpoint, just remember that the panels are
generally formed and cast on the floor slab, so connection details,
floor flatness and load tolerance of the floor slab should be considered.
Since the completed panels are generally lifted from the floor and set in place by crane,
panel design should consider that shear stress as well.

 

[UcfSE]

Some firms also increase the thickness of the floor slab so it doesn't crack with slab loads and gives you more concrete to brace to.

 

[JAE]

mdavis1 - Many (most) contractors use steel forms that come in even inch increments so the lumber dimensions you cite aren't usually a concern.

 

[frv]

JAE- That is not at all the case where I practice (Texas).

 

[hokie66]

neillydavies,

As your website indicates you are in Australia, a lot of the recommendations above about panel thicknesses, etc. may not apply. I have seen panels ranging in thickness from 120 to 250 mm, depending on the condition.

The Cement and Concrete Asssociation of Australia has some literature on tilt up construction and design, and has hosted a number of seminars where handouts were available. I suggest that may be your best initial source, along with discussing your jobs with a precaster. Much of the industrial work in Australia now is factory precast rather than job site tilt up. There is a tendency to load bearing precast, although there are still a lot of jobs with steel portals with the precast used as cladding.