Multidimensional nonlinear numerical simulation of post‐tensioned concrete girders with different prestressing levels

Abstract

Most of the Italian infrastructures have been built since the mid‐twentieth century. Prestressed concrete (PC) has been widely used, especially for bridges and viaducts. These structures have proved effective over time, but their performance could be affected by degradation phenomena (i.e., corrosion of the tendons and residual prestressing) or construction defects (i.e., grouting of the ducts), which need to be accurately modeled. This paper focuses on the flexural response of two reduced‐scale, posttensioned, PC bridge girders, prestressed with two different jacking forces and tested under four‐point bending configuration. Four multidimensional numerical models were developed to simulate the experimental behaviors of the selected specimens, using two alternative computational strategies, namely, the finite element method (FEM) and applied element method (AEM). Three FEM modeling were considered, ranging from one‐dimensional lumped‐plasticity models to two‐dimensional and three‐dimensional (3D) spread‐plasticity models. Besides, 3D AEM models were developed into another software package. The accuracy and the computational costs of the two numerical strategies are discussed in this paper. Also, the main features of each numerical modeling technique are addressed, including comparisons between numerical and experimental global response data as well as the statistical characterization of the model error. Based on these different features, the authors also suggest the most suitable numerical strategy for future studies on PC girders.

Flexural Stiffness and Crack Width of Partially Prestressed Beams with Unbonded Tendons

“…Furthermore, the "Kw" factors were proposed based on the difference between the measured crack widths and the widths determined by this expression (Equation ( 2)), and the graphs in Figures 30-37 were obtained in which this comparison is carried out. In these graphs (Figures [30][31][32][33][34][35][36][37], it is observed that the crack width determined analytically with this equation would be on the conservative side by obtaining higher values for the same acting moment. For the crack widths calculated with this expression, in some cases, there is a difference of up to 89% greater with respect to the crack width measured for the outer span centers and up to 94% greater for the case of the inner supports.…”

“…In general, in the previous graphs (Figures [30][31][32][33][34][35][36][37], the acting moment M a is represented in the ordinates, which is related to the crack width indicated on the abscissa for the different types of beams that were tested. It is shown that as the acting moment M a increases with respect to the cracking moment M cr , the crack width also begins to increase following the behavior of the proposed equation, which was compared to the crack widths obtained during the tests of the beams.…”

“…However, only prestressed members with bonded tendons were considered in these studies [29][30][31][32]. For unbonded tendons, only simple supported beam bridges were considered in these studies [33,34]. In the former, a simply supported PC beam was composed of a parabolic tendon and high-strength concrete, where short-and long-term prestressing losses were measured for approximately 9.5 months through the vibration response, and finite element modeling was also used to predict the dynamics of the girders; the latter focuses on the flexural response of two reduced-scale, post-tensioned, PC bridge girders, prestressed with two different jacking forces and tested under a fourpoint bending configuration, and these were also modeled with the finite element method to represent the actual behavior of the specimens.…”