Nueva metodología para el diseño de tubos de hormigón estructural

Abstract

The technical and economic suitability of using fibers has been proved in reinforced concrete pipes.However, the use of fibers in concrete pipe is slow, on the one hand due to the inertia to change in the construction field, and on the other hand due to the lack of a standardized, agile and reliable design method that accounts for the structural contribution of fibers. In this sense, this Doctoral Thesis aims to cover these aspects with regard to reinforced concrete pipes. For this purpose, a design method allows considering the strength contribution of the fibers in concrete pipes is proposed. Furthermore, in order to favour the spread of the results both to the scientific and the industrial community, the document of the Doctoral Thesis is presented as a compendium of articles accepted and / or in review status in scientific journals. Each of these articles presents the results of each of the lines of work and whose union has helped to achieve the main objective of this Doctoral Thesis. Firstly, the numerical tool Analysis of Evolutionary Sections (AES) developed to deal with the analysis of the strength response of reinforced concrete sections is presented. The tool is general and can simulate different reinforcement configurations (passive and/or active reinforcement with the possibility of incorporating fibers) and even the evolutionary construction of the section taking into account the rheological behaviour of materials. The model AES was subsequently used as a calculation tool of sections with the aim of addressing parametric studies as well as a subroutine into the other two models developed in the scope of this Doctoral Thesis. The second line of work focuses on the study of conventional reinforced concrete pipes. To address their optimal design the model Análisis de Tubos de Hormigón (ATH) has been developed. The practical interest of the model lies in the possibility of obtaining the optimal amount of reinforcement which meets the requirements in terms of bearing capacity specified in project. These reinforcements obtained from the models are, in most of the cases, inferior to the amounts in the design tables that are used traditionally. With the purpose of confirming the suitability of the ATH, an experimental campaign with tubes of 2800 mm of diameter has been carried out. By using the model, reductions up to 30% of the reinforcement have been obtained for pipes with the aforementioned diameter, while the differences in the bearing capacity do not exceed 10% when compared to the results of the three bearing edge test performed in the laboratory. The third and final line of work deepens into the technical and industrial side of the fiber reinforced concrete pipes. On the one hand, an extensive experimental campaign (some of it developed at the Universidade de São Paulo) is conducted, addressing issues associated with fiber reinforced concrete as well as others regarding the three edges test and the structural response of tubes of different diameters and with different amounts of fibers. On the other hand, the model for the Analysis of Pipes (MAP) was developed simultaneously for simulating the structural response of the fiber reinforced concrete pipes. The results of the bearing capacity of tubes up to 1000 mm of diameter tested have been compared with simulations performed with the MAP model, obtaining excellent correlations and not exceeding, in any case, the 5.5% relative error between the design loads. In view of the good results, it can be concluded that the design methodology herein presented, based on the use of the MAP model, ensures results that fit real behaviour and that the amounts of reinforcement provided are very close to the optimum necessary to meet the strength requirements established in each case.