Practical determination of prestress tendon profile by load-balancing method

Abstract

The determination of prestress tendon profile is a crucial step in the design of prestressed concrete structures. Like other design procedures, it is perceived to be a trial-and-error process. As an uncommon alternative to the conventional method of working out secondary moments and revising the tendon profile when the line of pressure falls out of the limiting zone, the load-balancing method offers great potential for direct determination of tendon profile. Though decades have passed since its proposition, there are still no comprehensive guidelines as to how the load-balancing method should be implemented. Issues regarding how much load should be balanced and how the method should be applied to two-dimensional structures etc have not been systemicalfy addressed. In this paper, the load-balancing method is revisited. Various considerations in the implementation of the method are discussed and two examples are presented to illustrate the step-by-step procedures. It is shown that the method is actually quite easy to implement, even in complicated structures like curved continuous bridges. Finally, it is advocated that the method is a much more efficient alternative to the conventional method and should be incorporated in the standard design process.