Estudio del requerimiento de armadura mínima en túneles de hormigón armado sometidos a presión interior y que utilizan hormigones de alta resistencia: consideraciones para determinar el acero mínimo de refuerzo en túneles diseñados con hormigón de alta resistencia.

Abstract

The objective of this document is to determine the minimum amount and provision of optimal flexural reinforcement steel for the manufacture of tunnel segments that use high-resistance concrete. To achieve this end, a compendium of theses, papers, regulations, and best practices was made. In addition, eighty-four tests were carried out with a representative finite element model of a segment using the Ansys software, where the number of steel bars placed was varied, from 1 to 9 bars, for different specimens of the same width (150 cm) characterized by; its height, amount of steel and compressive strength of concrete. The results of this thesis allow us to reduce the minimum amount of steel placed in tunnel segments proposed by the FHWA tunnel manual, which in turn is the same proposed by the ACI, by the minimum amount proposed by the Japanese standard JSCE- 07, which, being designed for use with high-strength concrete, is more accurate for this study; moreover, it considers the height of the specimen as an important variable in its calculation equation. Finally, it was possible to conclude that the minimum steel provisions that can be used for the construction of tunnel segments, to obtain an adequate behavior, are from 5 rods onwards, taking into account that from 7 rods the difference will not be relevant. The geometry of the section must be considered to grant the most appropriate arrangement and obtain good results, since, if the width manages to exceed the limits of this study (1.5 m), the most appropriate arrangements may be with a greater number of rods. To obtain optimal operation, the separation between rods should be between 25 centimeters or less.