Reinforcing Bar Placing

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Placing Rebar
See some general guidelines for rebar placing.

Reinforcing bar placing drawings are the instructions from the engineers to the contractors on how to build the structure to resist the anticipated loads. They provide the details and placing instructions so that the ironworkers can set the reinforcing bars into place in the formwork.

Bar Spacing

Placing drawings are used to show where the reinforcing bars to be placed. Sometimes the structural and placing drawings are very specific about exactly where rebar is placed. The ironworkers need to figure out how those rebars relate to the overall dimensions of the structure.

	Placing Reinforcing Bars, 8th Ed. This CRSI book outlines the work of the bar placers from the time steel is first delivered to the jobsite until it is completely placed and covered with concrete.
	Engineering Data Report #50: Placing Drawings This report defines and describes placing drawings, which are the detailed drawings for the reinforcing bars in cast-in-place reinforced concrete construction.

Bar Supports

The amount of concrete cover over the rebar is very important. If it's constructed properly, the concrete protects the rebar. Bar supports are used to hold the rebar up off the formwork or the ground to attain the proper depth of cover. They range from as simple as plain concrete blocks to plastic chairs, to wire bar supports.

Tying Requirements

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Tying Requirements
See how rebar should properly be tied in placing.

Rebar is tied together, using wire, to hold it in place.

Here's a diagram of typical ties:

• Detail A in the upper left—a "Snap Tie"—is the simplest and is usually used for rebar in a flat horizontal position.
• Detail B—the "Wrap and Snap Tie"—is normally used when tying vertical wall reinforcement to hold the bars securely into place.
• Detail C—the "Saddle Tie"—is more complicated than A or B but it's preferred in some parts of the country.
• Detail D—the "Wrap and Saddle Tie"-- is similar to the saddle tie except that the wire is wrapped 1-1/2 times around the first bar, then completed like detail C.
• Detail E—the "Figure Eight Tie"—can be used on walls in lieu of the Wrap and Snap.

Laps and Splices

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Splices
See how spliced rebar is installed.

While standard straight rebar comes in 60-foot lengths, many applications require longer lapped rebar. This is where laps or splices come in.

There are three kinds of splices: lap, mechanical, and welded.

Lap Splices

Lap splices are the predominant method of splicing and are the preferred method for mechanical or welded splices.

A lap is when two pieces of rebar are overlapped to create a continuous line of rebar. The length of the lap varies depending on the concrete strength, the rebar grade, size, and spacing. Contact splices—bars touch—are preferred because they are more secure against displacement during concrete operations. Non-contact lap-spliced bars should not be spaced too far apart.

When there is not enough space to do a lap splice, mechanical or welded splices are often used.

Welded Splices

CRSI recommends against manual arc welding in the field unless absoultely necessary. Consider mechanical splices as an alternative.

When arc welded splices are used, welding should conform to the AWS D1.4/D1.4M Welding Code published by the American Welding Society.

Welding of bars made from rail-steel and axle-steel reinforcing bars is not recommended.
Never permit field welding of crossing bars for the assembly of reinforcement.

Mechanical Splices

There are two general types of mechanical spices: couplers used to transfer tension and/or compression forces, and end-bearing devices for compression only.

This photo shows a number of different types of mechanical splice devices.

	Commonly Asked Technical Questions Concerning Cast-in-Place Reinforced Concrete Construction (EDR #44) CRSI's technical staff receives numerous inquiries about cast-in-place reinforced concrete construction.  This report provides answers to the most commonly asked technical questions.
	CRSI Manual of Standard Practice The Manual of Standard Practice has been presenting the standards of the reinforcing steel industry since 1927. Every architect, engineering firm, construction company and inspection office that is involved with reinforced concrete should own a copy.
	CRSI Reinforcement Anchorages and Splices, 4th Ed. The definitive source for information on development and splicing of reinforcing bars. Includes extensive tables of tension development and lap splice lengths for Grade 60 rebar with 3,000 to 8,000 psi concrete compressive strengths, and development and lap splice tables for epoxy-coated reinforcing bars. Based on ACI 318-95.

Tolerances

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Tolerances
Basic guidelines for tolerances in shearing, placing, splicing and formwork.

Construction is not an exact science. While project plans and specifications should be followed, it's important to know where the rebar must be placed accurately and where there is room to field-adjust if necessary.

As a rule, in long runs of slabs or walls, the exact spacing is not important as the total number of bars.

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