Verificación experimental de uniones mediante lazos de armadura y su aplicación en la construcción evolutiva de puentes
Authors:   , Contreras López Catalina del Pilar 
Published: July 2023

The box-girder is currently the solution for large prestressed concrete bridges, being most used today in steel and mixed structures. Their widespread use is due to the strength characteristics and versatility, using various construction processes depending on the conditions of the work. However, it has the great disadvantage that the concrete should be done in phases. Because of the advantages of this section is really important develop new techniques to improve the performance, and reduce construction times.
The construction of the top slab involves extension straight joints. It has been observed that this kind of joint requires additional measures during execution, either from the point of view of the danger to operators or remove the inside formwork. As a result, it is needed propose a new type of joint, by loops, reducing risks, minimizing the construction times and making easier the work on site.
To understand the behaviour of a structure with this loop joint, are built concrete sections with representative dimensions of a railway bridge, with a concrete joint, reproducing, as far as possible, what happens in reality. These sections will be tested experimentally. In a previous study has been analysed the performance in a simple bending test. For this reason, in this study is checked the response in pure bending.
Dynamic and static campaigns are done, using for this a total of 8 slabs, existing three types of union based on European codes:
- Reference Slab (LR) with a continuous reinforcement
- DIN Slab (LD) with a loop joint according to DIN 1045
- Experimental Slab (LE) with the proposed loop joint
With these results it is possible to know the performance until failure, under static and dynamics loads with a number of cycles of 2 x 10^6.
In static load campaign are tested 3 slabs, representatives of the different types of continuity. With these results is possible to make a comparison between the behaviour of the slabs associated with: longitudinal and transverse strain, deflections and concrete joint opening.
In dynamic load campaign are tested 5 slabs, three of them with the same type of reinforcement and the other two representatives of the others types. In each of these tests are applied different load ranges, depending on the objectives, defining 5 tests:
1. LR:	¿s=150 MPa --> Q_max=141 kN y Q_min=50 kN
2. LD:	¿s=150 MPa -->	Q_max=141 kN y Q_min=50 kN
3. LE_2:	¿s=150 MPa -->	Q_max=141 kN y Q_min=50 kN
4. LE_3:	¿s=150 MPa -->	Q_max=210 kN y Q_min=119 kN
5. LE_4:	¿s=127 MPa -->	Q_max=125 kN y Q_min=47 kN
Based on the test load levels, are made comparisons between these results and the results obtained for an experimental slab under simple bending (L.F.S.), associated to: dynamic deflection, concrete joint opening, longitudinal and transverse strain, and failure loads after finished dynamic tests.
Finally, are proposed futures research works, in order to increase the knowledge associated with a loop joint reinforcement under another type of efforts.