Rebar Support 4

[alrobbo]

I have recently received information from an associate whom has just returned from the 2008 ConExpo. During the Expo he was approached by several people enquiring as to the extruded plastic rebar support ( bar chairs ) he was he using in an exhibit. He was queried as to where he obtained these plastic rebar support ( bar chairs )as they had not seen anything similar in the States. If this is the case what method is employed to hold the rebar in position.

 

[dicksewerrat]

I saw plastic chairs 15 years ago. Also metal ones.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[alrobbo]

Good Morning Richard

Thanks for your prompt reply to my query. Can you advise if the use of plastic bar chairs within the States is common practice.

 

[dicksewerrat]

I have been out of the business of constructing reinforced structures for a 7-8 years, so I can't say. Call some large contractors and chat with them about this.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[civilperson]

Chairs are common usage in commercial, industrial, heavy highway and high rise construction. Residential typically uses concrete bricks for supports of tied bar mats, (or what ever they can get away with in the absence of a inspector).

 

[alrobbo]

G'day Civilperson

Thanks for the confirmation. I found it hard to believe plastic bar chairs would not be commonly used on projects in States. Plastic / metal bar chairs are used extensively thru Australia.

 

[boffintech]

I currently inspect on several hi-rise projects and the use of plastic rebar support chairs is strictly prohibited by the EOR. The requirement is for plastic tipped steel class 1 support chairs.


Because they are incapable of supporting men and materials I never like to see the use of these plastic rebar support chairs for elevated slab work.

 

[alrobbo]

G'day Boffintech

Within Australia plastic bar chairs are used extensively in suspended slabs, beams and columns. I have never experienced any failure of the plastic bar chairs, nor have I ever heard of a failure. The plastic bar chairs are more than capable of supporting both materials and men.

Can you direct me to a supplier or manufacturer of plastic rebar chairs within the States as I'm interested as to the differences between the chairs as used within each country.

Thanks for the information.

 

[boffintech]

Never heard of a broken plastic rebar support chair? Amazing.

All I can tell you is that I inspect suspended slabs daily, and as a result I see broken plastic rebar support chairs daily. I'll take some digitals and see if I can post them. The worst ones are the ones over 6 1/2" because they are made up of two chairs zip-tied together. Any kind of twisting or lateral loading and they just pop apart of fold up.

 

[alrobbo]

G'day boffintech

Thanks for the information.

The problems I have encountered with the plastic tipped metal bar chairs is the tendency to tip over due to the small footprint plus they are only designed to carry one bar. The plastic chairs are combinations where both top & bottom steel of the mat can be carried with a single chair.

Metal tipped bar chairs are available and utilized by some people given the size of bar chairs range from 20 mm to 360 mm high. The metal chairs are commonly used during slab on ground construction

 

[alrobbo]

G'day boffintech

I have spoken to our local rebar suppliers, both small and large outlets, and queried the ratio of sales between plastic and metal bar chairs.

The general opinion was for very 1000 bags of plastic bag chairs sold they will sell less than 10 bag of metal bar chairs.

I can only assume from your previous statements the relative strength of plastic bar chairs are different, be it due to the materials, design or fixing practices.

Thanks

 

[Epolkowski]

I am a rebar detailer working for companies throughout the eastern US. Rebar supports vary by supplier and location. The CRSI, a governing concrete reinforcing body in the US, does not have any specific qualifications regarding bar supports. Typically, supports are not specific so that 1) the rebar placer can use what they typical use and prefer. And 2)the fabricator can use the cheapest or most available item (usually what they stock or have product line for). There are a number of companies that make the plastic chairs and are routinely becoming more commonplace in use. The Dayton Superior Aztec listed above is common and a good product. The chairs, in years past, were insufficient in supporting the bar correctly. Usually with foot traffic over the mats, the legs would torque and shear, causing failure. Over time they have been better designed and constructed. Also, their price has come down and made them more competitive in cost. With oil prices, they cost more. Or so they claimed. The EOR can spec whether or not to use them. They have final call. The alternative or more traditional was a , metal chair, with or with out plastic dipped feet or with runners. These could be galvanized or epoxy coated, based on application required. Bars on grade are typically held up on blocks of same strength as concrete used. Upper mats greater than 12" can also be supported by standees, rebar bent in z pattern to act as supt.

 

[alrobbo]

G'day Epolkowski

Thanks for your detailed reply to my initinal query. As a general observation it appears the building practices within the US involves a wide variety of bar chairs.

Again many thanks.