DIRECT METHOD FOR ANALYSIS OF PRESSTRESSED CONCRETESTRUCTURE

Abstract

One of significant progress of construction industry is prestressed concrete. The range of applications is very wide in the high-rise buildings, large-span buildings and the bridges. Prestressed concrete has been successfully used for small as well as large projects over the last sixty years. The efficiency stems from being able to use high strength materials, to structurally utilize the entire cross section, to vary the force and location of the reinforcing to best resist applied loads, and to control the timing of when the prestressing force is applied to the structure. In prestressed concrete structures, load balancing is an indirect and familiar method for analyzing prestressed members through equivalent load. The frame being subjected to equivalent load produces balanced moment or prestressing moment (it is taken into account in serviceability limit state) and reactions; then, secondary moment (it is taken into account in ultimate limit state) is produced by reactions. The paper presents a direct method for analyzing prestressed members by solving the differential equations of the elastic line. These differential equations consider the equilibrium of the reactions and eccentricity of the prestressing force. After solving these equations, the engineers can directly obtain the reactions; and subsequently, determine the prestressing moment, secondary moment and shear force. The direct method also finds out the precise effect resulting from large tendon sag in transfer or deep beam. Effect of large tendon sag is the same as small tendon sag, the differences are very small. Besides, in this paper, the equivalent load models associated with any complicated tendon profiles which are formularized deal with and expand the unconventional tendon profile in the future of construction industry.