UFC 3-260-02
30 June 2001
CHAPTER 16
PRESTRESSED CONCRETE PAVEMENT DESIGN
1. BASIS OF DESIGN. A prestressed concrete pavement is one in which a significant compressive
stress has been induced in both the longitudinal and transverse directions prior to the application of a
live load. The induced compressive stress offsets the damaging effects of tensile stresses resulting from
applied live loads and permits the formation of momentary, or partial, plastic hinges under passage of
wheel loads that change the failure mode from tensile cracking at the bottom of the pavement to tensile
cracking in the upper surface of the pavement due to negative moments. These two factors permit the
prestressed concrete pavement to carry substantially greater loadings than equal thickness of plain
concrete or reinforced concrete pavement and still provide a functionally adequate pavement.
2. UNITS. The design equations and criteria in this chapter are controlled by English units.
Therefore, the equations have not been converted to SI units.
3. USES FOR PRESTRESSED CONCRETE PAVEMENT. Although prestressed concrete pavements
have been used in Europe, a long-time performance history of prestressed concrete pavements in the
United States is not extensive. Therefore, its use will require the approval of HQUSACE (CEMP), the
approval Air Force Major Command, or Naval Facilities Engineering Command. Several test or
demonstration sections in the United States have shown good performance, but problems have been
experienced with joints between long prestressed sections where large movements are experienced.
For this reason, complex joints and extreme care are required during construction. The selection of
prestressed concrete pavements should be based upon the economics involved.
4.
FOUNDATION REQUIREMENTS.
a. Subgrade and base. In general, the subgrade for a prestressed concrete pavement will be
treated and evaluated in the same manner as for other types of rigid pavements. The reduced thickness
of prestressed concrete pavement will result in a more flexible system and higher vertical stresses in the
foundation than for plain concrete pavements. For this reason, the quality and strength of the foundation
becomes more important. The foundation should be strengthened through the use of a high-quality
(stabilized or nonstabilized) base course and/or stabilized or modified subgrade to provide a minimum
modulus of soil reaction or composite modulus of soil reaction of 54 kPa/mm (200 pcl). In addition,
because the amount of design prestress is a function of the foundation restraint, the surface of the
foundation should be finished as smooth and as free of undulations, holes, etc., as possible.
b. Friction-Reduction Layer. A friction-reducing layer shall be used between the prestressed
concrete pavement and the foundation. A satisfactory friction-reducing layer may consist of two
polyethylene sheets over a thin 6- to 13-millimeter (1/4- to 1/2-inch) uniform size sand layer. The sand
layer is used primarily to smooth out the surface irregularities of the foundation. Other types of friction-
reducing material may be considered.
5. METHOD OF PRESTRESSING. Pavements may be prestressed using pretensioning or
posttensioning. The method most commonly used for pavements is posttensioning, in which tendons
are installed before concrete placement and stressed after concrete placement. The tendons either are
placed in conduits or are plastic-encased to prevent bonding with the concrete. The tendons are
threaded through bearing plates cast into the face of the concrete at the ends or sides of the concrete
slabs. After the concrete has gained sufficient strength, the tendons are stressed, using the bearing
16-1
Previous Page
