The RoboShot@FRC project aims to be a contribution to the European strategy that foresees the development of the trans-European transport network (TEN-T), which connects Europe from East to West and from North to South, through the optimized integration of all means transport systems that maximize efficiency, comfort, economy and environmental costs.

For a paradigm shift in the preferential use of rail transport of people and goods, it is necessary to significantly increase the technology for manufacturing, rehabilitation and reinforcement of the lining of railway tunnels. This must be ensured through an integrated strategy, involving the use of more developed and higher performance materials, their application using robotization coupled with improvements in inspection and diagnosis, spatial and event (damage) digitalization, and the sizing of structures in fiber reinforced concrete (BRF) (known by the English acronym FRC - Fiber Reinforced Concrete) that take advantage of the technical-economic advantages of this composite.

Fiber fibers have been used as reinforcement of cementitious matrix materials to increase their resistance to post-cracking attraction, energy absorption and dissipation capacity, impact resistance and to prevent their disintegration by fire. These technical advantages are associated with economic advantages that derive from being able to partially, and even completely, eliminate casual reinforcement, given that the costs of adding fibers are practically limited to the material, as they are additional to any constituent of the concrete.

Due to these advantages, BRF has been used to stabilize and reinforce tunnel walls using the projection technique. However, it is recognized that due to the geometry of the tunnel, lithological characteristics of the substrate, existence or not of faults and diaclases, and other site specificities, the thickness of the BRF layer to be applied, as well as the type and quantity of fibers , must take into account the results obtained in a stability project (structural/geotechnical) supported by advanced structural analysis models that also take into account the real fiber reinforcement mechanisms. This means that the thickness of the BRF layer, and the quantity and types of fibers, may vary spatially in the tunnel, recommending the application of BRF according to robotic projection technology in accordance with the conditions obtained in the stability project. However, current projection equipment does not allow the application of BRF according to these requirements.

The RoboShot@FRC project therefore has the essential objective of developing a new generation of projection head, supported on a robotic arm, capable of applying BRF in tunnels, respecting, in an automated way, the requirements of the stability project. Furthermore, this projection head must allow the application of more than one type of fibers in order to mobilize the material and structural advantages of hybrid reinforcement. In the case of tunnels, a hybrid system formed by fibers with a low and high modulus of elasticity guarantees complementary reinforcement functions. In fact, low modulus fibers, volatilizable above a certain temperature, have the main functions of controlling shrinkage cracking and preventing the disintegration of concrete under fire, while fibers with a high modulus of elasticity (normally called structural fibers) guarantee the level of post-cracking resistance desired for the concrete.

For an integrated and optimized efficiency of the robotic system that is intended to be developed, this project mobilizes innovative activities throughout the chain that encompasses a tunnel stability project, as well as partners who in Portugal are recognized as having more experience and knowledge in the areas in question, namely:

1. Infraestruturas de Portugal (IP), which manages the national railway tunnel network, intends to develop a BIM (Building Information Modelling) platform to characterize this network and the associated risks and damages, as well as databases on geometry, damages and all aspects relevant to network management for decision making, and for interface with calculation models. This information will be constantly updated, and will be provided to the consortium to investigate construction/renovation/strengthening strategies for the railway network. The platform will include a module representing the 3D geometry of the tunnel, with location of the type and size of damage in a format suitable for interpretation by structural analysis and sizing models.

2. The team from the University of Minho (UM), through the Structural Composites (SC) research group, will use the current IP tunnel characterization database to generate data metafiles for the software for designing concrete structures Reinforced with Fibers (BRF) in the construction/renovation/reinforcement of railway tunnels to be applied according to the robotic technology to be developed within the scope of the project. To effectively model the fiber reinforcement mechanisms in the BRF applied using this technology, UM-SC will develop new constitutive models capable of taking into account the orientation and distribution of fibers. The results in text and graphic format of the BRF structure project to be applied in the construction/renovation/reinforcement of tunnels will be coded for proper reading by the platform to be developed by the Leiria Polytechnic group to control the robotic BRF application system.

3. In parallel, EPOS, a company with extensive experience in the construction, renovation and reinforcement of tunnels using various technologies, namely BRF projection, will develop a new methodology for optimizing the BRF, capable of effectively mobilizing the reinforcement mechanisms of fibers in the BRF frame applied according to BRF robotic projection technology. You will be responsible for creating test pieces and prototypes for laboratory and in situ experimental programs, as well as applying advanced inspection and diagnostic techniques to assist IP in gathering information for its BIM platform, for example, with regard to the lithological constitution of the tunnels and identification and characterization of damage.

4. At the same time, teams from the Polytechnic of Leiria, Leirimetal and Teclis will create the robotic system for optimized projection of fiber-reinforced concrete in railway tunnels, which involves developing:

  • Computational platform to read the BRF stability project carried out by UM-SC (already formatted in accordance with the communication protocol to be established) and generate information to control the trajectories of the robotic system so that it can design the BRF in accordance with the prescriptions of the stability project mentioned above. This development will be carried out by the Polytechnic of Leiria.
  • The projection head and its handling, operation and control systems. This head must be fed in order to project the concrete mixed with two different types of fibers, guaranteeing the possibility of applying different amounts and types of fibers according to the requirements of the stability project. The projection heads used in current BRF projection equipment in tunnels only have the possibility of using fibers that are already pre-mixed in the concrete at the time the BRF is designed, therefore it is not possible to optimize the use of fibers , applying them in type and quantity according to the requirements of the stability project of each area to be rehabilitated. This work will be carried out mainly by Leirimetal and Teclis.
  • The control system of both the robotic arm that supports the new generation of projection head, and the optimized BRF projection process, with the ability, in a closed loop, to guarantee compliance with the deposition specifications contained in the stability project, through continuous measurement of the quality of the work performed. The Leiria Polytechnic will be responsible for developing the control and monitoring system for the deposition process, while Leirimetal will focus on the robotic electromechanical system.

5. To model the distribution and orientation of the fibers, experimental research methodologies capable of identifying the fibers inside the concrete will also be developed. The properties of BRF will be characterized by tests capable of identifying the specificities introduced into the behavior of this material by the technique of its application. Finally, innovative techniques will also be used to evaluate the appropriate application of the BRF.

 

The five major areas of research

1. BIM platform for characterizing the railway tunnel network with metafile for advanced analysis of damage and pathologies in tunnels and their locations.
2. Computational model for nonlinear material analysis of fiber-reinforced concrete structures with explicit modeling of cracks and fibers, and soil-structure interaction.
3. Methodologies for evaluating the orientation and distribution of fibers in the BRF.
4. Development of a BRF optimization methodology to integrate the requirements of the new projection technology.
5. Management and control system for the new generation of BRF projection head.
6. Robotic system for optimized, closed-loop projection of BRF in railway tunnels.


To achieve the objectives, the consortium, in particular Leirimetal, Teclis and the Polytechnic of Leiria, will develop the following approach:

1. The Polytechnic of Leiria will develop a computer tool for reading the results files of the stability project developed by UM-SC and its suitability for controlling the robotic application of the BRF.

2. Leirimetal will rent a projection machine similar to the one in Annex B, which will serve as a “laboratory” for the development of the remote control system, the robotic arm and the new projection head, using everything else to support the total system operation during investigation and testing.

3. Leirimetal will acquire a robotic arm from the market that can support a projection head weighing up to 100 kg and develop the projection head actuation system.

4. The Polytechnic of Leiria will develop a software package for generating trajectories for the vehicle + deposition robot set, so that the reinforcement result meets the project requirements.

5. The Leiria Polytechnic will develop the vehicle's automatic control system and robotic projection/deposition system, minimizing the human factor, in collaboration with Leirimetal. This system takes as input the trajectories generated in the previous point and involves monitoring the deposition system during the projection process and the positioning of the vehicle in relation to the tunnel, using the information on the BIM platform as a reference.

6. The Polytechnic of Leiria, Leirimetal and Teclis will develop, in close collaboration with EPOS, which uses this equipment daily and with UM-SC, the new projection head in which the fibers will be joined to the concrete. The head will integrate a system [4] that will have the capacity to read the target surface of the projection, cross-reference this information with that recorded on IP's BIM platform and, depending on the characteristics measured in situ, optimize, with the tool developed by EPOS in the activity 3, the BRF projection parameters.

 

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