Resumen de Diseño y validación experimental de uniones mediante superposición con lazos de armaduras en viaductos de hormigón de sección transversal evolutiva: optimización del proceso constructivo
Bridges construction is in steady progress in technological innovation and systematization of the construction process to improve yields in the implementation, ensuring the safety and quality, and to achieve a rationalization of means employed.
The current technique for segmental construction of concrete viaducts, and specifically those in which construction of the cross section is implemented in two phases, leads to limited performance and handling inside the cross section. In a first stage, the "U" drawer including bottom slab and webs is executed. In a second stage is built the upper slab until completing the drawer. Usually, the use of splices by overlapping bars (force transfer between two spliced bars) often leads significant lengths. Moreover, these procedures involve construction difficulties in the withdrawal of the slab inner through the upper hole.
Identified the current situation and existing constraints in unusual construction procedures, the objective of this thesis is to design, develop, and check experimentally a typology of structural link between segments with limited length. The design concept is based in a development length to anchorage of hook reinforcement sewn inside with transverse reinforcement bars. In order to investigate the stiffness and strength of the loop joints, experimental studies were conducted. Two types of loading tests were performed which are static loading tests (8 slabs) and fatigue loading tests (8 slabs). The test variables are the diameter of the loop bars ( 20 and 25) and the width of the loop joint. Cracking, ultimate behaviour (to breakage) and fatigue behaviour of the loop joints were observed and compared with the behaviour of slabs without loop joints.
From the test results, in static load tests, the mechanical behaviour of the loop joints was confirmed similar to slabs without joints.The tests results (fatigue load tests) indicate that a reinforced concrete element subject to bending, show a progressive reduction of stiffness with increase of crack widths and residual deflections. In the case to loop joint design it's heightened by the limited width length. The results of the second test results validate the loop joint proposed, if satisfy reductions proposed in various Codes and Regulations. Also, the failures in different specimens (with loop joints and without) are obtained in these tests. Consequently, details of the loop joints in based on fatigue tests results are suggested.
Finally, from the studies carried out in this Thesis, different research topics as areas for future are suggested.
