David Garcia-Sanchez

Compared with igneous and metamorphic ballast materials, limestone ballast is more prone to rapid degradation, particularly when rigid concrete sleepers impose localized stresses on the ballast bed. Such stress concentrations can accelerate ballast crushing, settlement accumulation, lateral spreading, and support loss, ultimately contributing to floating sleepers and sleeper deterioration. To address these challenges, this study investigates a resilient rubber-modified concrete sleeper with a geotextile under-sleeper pad using a large-scale ballasted track model. The experimental program included two large-scale prototype configurations tested using limestone ballast: a conventional monoblock concrete sleeper and a rubber-modified concrete sleeper with a geotextile underpad. The tests were conducted under cyclic loading up to 3 million cycles. The modified sleeper system exhibited greater initial bedding-in settlement due to its flexibility and earlier ballast densification. After this stage, however, settlement accumulated more slowly, reducing the final permanent settlement from 28 mm to 26 mm. The modified system also produced a more uniform support condition, reduced the tendency for center binding, and generated a broader sleeper–ballast contact area with lower stress concentration. Although higher reinforcement strains developed in the rubber-modified sleeper owing to its lower flexural stiffness, no visible cracking or distress was observed. Overall, these findings show that the rubber-modified concrete sleeper with a geotextile underpad improves the performance of limestone-ballasted track mainly by enhancing load redistribution, stabilizing support conditions, and reducing local stress concentration beneath the sleeper.

The design of bridge decks requires accurate transverse live load distribution; however, existing simplified methods like beam models fail to capture cross-section bending and distortion, while traditional Load Distribution Factors (LDFs) provide only approximate values for the most stressed beam. This study introduces a novel method to fill this gap by applying a virtual model that reduces the structural problem to two degrees of freedom per longitudinal rib: deflection and rotation. Unlike prior models, this approach explicitly accounts for increased torsional and transverse bending stiffness in box sections and incorporates distortion through a reduced shear area calculation. The methodology was validated through a parametric study of 75 box-girder decks involving 175 load states, alongside two experimental tests: a small-scale laboratory section and a full-scale load test of the Arlanzon Viaduct. Findings demonstrate a maximum divergence of less than 14% compared to traditional Finite Element Methods (FEM), with a mean error below 8%. Experimental results showed an accuracy level comparable to complex FEM models. This method significantly optimizes calculation time and material resources, offering a reliable alternative for bridge design using modern materials without requiring high computational power.

Long-term structural monitoring of railway tunnels is essential for understanding slow deformation processes and supporting informed maintenance decisions. However, strain measurements collected over extended periods are often dominated by environmental effects, particularly temperature variations, which can mask mechanically meaningful behaviour. This challenge is exacerbated when temperature sensors fail or are unavailable, limiting the applicability of conventional compensation strategies.,This paper presents an unsupervised, data-driven thermal compensation framework for fibre Bragg grating (FBG) strain measurements based on Singular Value Decomposition–driven Principal Component Analysis (PCA). The proposed approach reconstructs a virtual thermal reference directly from strain data, enabling separation of dominant thermal effects without relying on external temperature measurements. Higher-order PCA modes are further exploited to identify sensor-specific drift and anomalous behaviour, allowing fault-tolerant correction through sensor-adaptive scaling.,The methodology is validated using long-term monitoring data acquired from an operational railway tunnel located in Artxanda, Bilbao (Spain). Results demonstrate that the dominant low-frequency thermal component can be effectively isolated, revealing consistent day–night strain offsets and significantly reducing thermal masking across the sensor array. Spectral coherence analysis confirms that the correction preserves mechanically meaningful dynamic content associated with train passages, avoiding over-filtering. Residual low-frequency trends are shown to be smooth and physically plausible, while sensors affected by installation- or system-related artefacts are automatically identified and treated conservatively.,The proposed framework provides a robust and practical solution for long-term tunnel monitoring under incomplete instrumentation conditions, enabling reliable interpretation of strain measurements in real operational environments.

In response to construction challenges, the Liaison project is developing an off-siteconcept for optimized RC members derived from an initial version (RCB-2.0) thatincorporates complex formworks, designed using an original analytical optimizationprocess (SOM), and 3D-printed with clay. The improved concept (RCB-2.1) makesgreater use of digital technologies to save more concrete and increase industrialscalability. The digital twins of as-built steel reinforcement cages are created using alaser tracker, enabling the 3D printing of custom-made low-carbon cementitious mortarformworks. Four 7-meter-long beams, structurally optimized, incorporating a fiber-opticBragg grating and 35% recycled aggregates were manufactured and experimentallytested (four-point bending test). They demonstrated the expected behavior in terms ofstiffness, ductility, and strength, and are now a part of a footbridge in Spain. Newpossibilities for more material savings, up to 50%, particularly through quality controland design, are also being explored and discussed.

One of the activities that can most influence climate neutrality is the activity of infrastructure construction. Some countries already include environmental concepts in the development of their infrastructures, as an approximation to neutrality, but this is insufficient, it is necessary to be more ambitious, and define in a broad and global way, a governance framework that includes this concept in detail, throughout their life cycle. To this end, a methodology is proposed that defines the neutrality of infrastructures based on circularity, including this concept in governance processes, through circularity indicators. In addition, to show its validity, it is applied to the contracting in the construction phase of the A-67 Highway project, Capacity Expansion, in Spain. Obtaining very good improvements in infrastructure governance, thus contributing to climate neutrality.

Liaison Horizon Europe Project provides knowledge and technical solutions to limit transport infrastructures (TI) emissions, both caused by transport infrastructure itself and to which transport infrastructure contributes. This project covers the whole life cycle of TI to which extent TI design can influence and limit the overall emissions from construction, maintenance, operation and decommissioning of the infrastructure in a digital environment for next future TI. Liaison adopts a holistic approach to tackle this challenge, because the development of particular technical solutions is not sufficient to achieve low environmental impact TI if they are not part of a broader strategy. The only effective way to ensure the implementation of paradigm-shifting technical solutions in the TI sector is to implement a governance framework (Dynamic Multi-Infrastructure Governance Framework -DMIGF) that activates, articulates, and monitors compliance with circular economy principles throughout the life of the infrastructure when developing and implementing these solutions. Liaison develops smart and sustainable beams, rigid road pavements and improved ballast; bio-asphalt and smart pavement inspection system; intelligent tunnel control system and photovoltaic guardrails.

One of the most common challenges in maintaining viaduct decks in optimal condition is ensuring the durability and performance of road expansion joints (REJ). These elements are particularly susceptible to deterioration due to the continuous impact and dynamic loads generated by heavy vehicle traffic. This study focuses on the structural response of flexible REJ under such conditions and proposes an optimized method for simplified analysis of their behavior. The proposed methodology is validated through both theoretical and empirical approaches. The theoretical analysis compares the structural response of flexible REJ subjected to heavy vehicles at varying speeds, contrasting the results obtained using the proposed method with those derived from traditional Finite Element Method (FEM) simulations. Meanwhile, the empirical analysis is conducted by monitoring the in-service behavior of a flexible REJ installed on a pergola over a railway line within the Spanish motorway network. The findings demonstrate that the proposed approach provides reliable results while significantly reducing computational time, energy consumption, and CO₂ emissions compared to conventional methods. Furthermore, its straightforward integration into digital asset management systems enhances its applicability for infrastructure maintenance, offering a cost-effective and sustainable solution for optimizing the service life of REJ.