Numerical analysis of continuous beams prestressed with external tendons

This paper presents a numerical model conceived to simulate the behavior up to collapse of continuous concrete beams prestressed with bonded or external tendons. Its most valuable feature is the ability to automatically determine the most suitable extent of each load increment according to the actual stiffness of all the segments that form the discretized beam. A crucial problem of nonlinear structural analysis is numerical evaluation of the rotation capacity of plastic hinges, especially when dealing with concrete beams prestressed with external tendons, which is a technology nowadays increasingly adopted in new continuous bridges and in the rehabilitation or strengthening of old or damaged structures. This problem is discussed in depth and a simple rule, which differs from those usually discussed in the scientific literature, is adopted to subdivide the beam into discrete elements. The effectiveness of the numerical model is tested by comparing its numerical output with the outcomes of 14 experimental tests. This comparison looks promising since the mean value of the error on load carrying capacity is only 0.1%, with a 2.4% standard deviation.