Quantcast REINFORCING STEEL DESIGN - conitnued

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UFC 3-260-02
30 June 2001
c. Type of Reinforcing Steel. The reinforcing steel may be either deformed bars conforming to
ASTM A 615 or welded deformed steel wire fabric conforming to ASTM A 497. Generally, longitudinal
reinforcement is provided by deformed billet bars with 413-MPa (60,000-psi) minimum yield strength;
however, other grades may be used. A grade 40 deformed bar should be used for the transverse
reinforcement or for tie bars if bending is anticipated during construction.
d. Placement of Reinforcing Steel. When the slab thickness is 203 millimeters (8 inches) or less,
the longitudinal reinforcement should be placed at the middepth of the slab. For thickness in excess of
200 millimeters (8 inches), the longitudinal steel should be placed slightly above the middepth, but a
minimum cover of 75 millimeters (3 inches) of concrete shall be maintained in all cases. Transverse
reinforcement is normally placed below and used to support the longitudinal steel; however, it may be
placed on top of the longitudinal steel if the minimum of 75 millimeters (3 inches) of concrete cover is
maintained. Proper lapping of the longitudinal reinforcement is important from the standpoint of load
development and is essential for true continuity in the steel. The deformed bars or welded deformed
wire fabric shall be lapped in accordance with Chapter 15. It is particularly important to stagger the laps
in the reinforcing steel. Generally, not more than one-third to one-half of the longitudinal steel should be
spliced in a single transverse plane across a paving lane. The width of this plane should be
610 millimeters (24 inches) if the one-third figure is used, and 1,220 millimeters (48 inches) if the one-
half requirement is used. The latter case shall be interpreted to read that not more than one-half of the
longitudinal reinforcing members may be spliced in any 1,220-millimeter (48-inch) length of pavement.
The stagger of laps with deformed bars may be on a continuous basis rather than the one-third or one-
half detail described above.
6. TERMINAL DESIGN. When appreciable lengths of continuously reinforced concrete pavement are
used, the ends experience large movements if unrestrained and will exert large forces if restrained. To
protect abutting pavements or structures from damage, the ends of continuously reinforced concrete
pavements must be either isolated or restrained. Experience has shown that it is practically impossible
to completely restrain or completely isolate the pavement ends, and a combination of these schemes
(that is, partial restrain and limited available expansion space) has proven practical. End anchorage
and/or expansion joints must be provided when continuously reinforced concrete pavement is not
continuous through intersections or when it abuts a structure. Although numerous terminal treatment
systems have been attempted, especially on highway pavements, the most successful system appears
to be the wide-flange beam joint. Typical drawings of this terminal system are shown in Figure 15-1. For
runways, the continuously reinforced concrete pavement should extend to the runway end, where the
wide-flange beam joint would be placed as a part of the overrun area.
7. JOINTING. Continuously reinforced concrete pavements will normally use the same type of joints as
used for plain concrete pavements except that contraction joints are not normally required. Longitudinal
construction joints will be required with the spacing dictated by the paving equipment. The longitudinal
construction joints will be butt joints as shown in Figure 12-32. Transverse construction joints, which are
required for construction expediency, will be designed to provide slab continuity by continuing the normal
longitudinal steel through the joint. The normal reinforcement will be supplemented by additional steel
bars, 1.5 meters (5 feet) long (0.75 meters (2.5 feet) on each side of the joint) and the same diameter as
the longitudinal reinforcement. The additional steel will be placed between the normal reinforcement
and at the same depth in the slab. Thickened-edge slip joints will be used at intersections of pavements
where slippage will occur. Otherwise, doweled expansion joints will be used. Expansion joint design will
be in accordance with Chapter 12. It will be necessary to provide for expansion at all barriers located in
or adjacent to continuously reinforced concrete pavement.

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