BEHAVIOUR OF PRESTRESSED CONCRETE PAVEMENT UNDER STATIC LOADS

Abstract

The application of prestressing technique for highway and airport pavements is a relatively recent development. The inherent advantages of prestressed concrete pavement are the higher load carrying capacity and the fewer expansion joints in the pavement. The latter improves the riding surface of the pavement. The object of this. investigation is to determine the stress deformation characteristics of prestressed concrete pavement under static loads. For this purpose one slab of dimensions 3m x 3m x 10 erns was laid in the field* The pavement slab was prestressed, only in one direction, to 14 Kgicm2. For'prestressing, Udall-Gifford method of post tensioning was adopted. Static load tests were conducted in ail the critical load positions with varying plate diameters viz. 45, 30, 20 and 16 ems. Attempt was made to load the pavement upto failure. The testing was carried out under "no warping" condition. The results have been compared with the results of similar tests on 10 ems thick plain cement concrete pavement* The comparison indicates that within the elastic range of loading, the structural performance of the prestressed pavement slab is similar to that 'of plain cement concrete pavement, with an exception that the magnitude of the extreme fibre stress can be increased above the flexural strength of concrete by an amount equal to the prestress. It has further been observed that, for slab dimensions as adopted in this investigation, one way prestressing does not alter the structural behaviour of prestressed concrete pavement along the direction of prestressing when compared with the transverse direction. Due to the limited capacity of loading device only the edge and corner regions of the pavement could be broken. with 20 ems and 15 ems loading plates. The cracks first appeared with 20 ems plate diameter and On immediately releasing the load, it was observed that the cracks closed up. This may be due to the initial compression applied to the pavement slab, which helps-in restoring the aggregate interlocking, thus closing the cracks developed. The crack patterns of the edge and corner regions have been reported. Based on the cracking load of the prestressed concrete pavement at the edge region and using Westergaard equation for the above region; it has been found that 20.5 ems thick plain cement concrete pavement is equivalent to 10 ems thick prestressec concrete pavement having one way prestressing of 14 KgieW. The economic analysis of prestressed concrete pavement in respect of its construction cost has also been carried out. The adoption of prestressed concrete pavement results in the savings by about 40 per cent over the constriction cost of its equivalent plain cement concrete pavement, *********