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An assessment concerning the structural applicability and performance of fiber reinforced concrete (FRC) is presented for different bridge elements and within a design framework. FRC as the main bearing material in structural members has evolved from low-demand applications to increasingly ones, where bending and shear are the main internal forces. In actual applications, this was reflected with initial slab-on-grade cases, through tunnels, and later moving towards elevated slabs. Past experiences show that FRC has notable features regarding ultimate capacity and serviceability performance (i.e., enhanced crack control). These capabilities allowed for optimizations such as material savings, reduction of intensive labor during construction, or extended durability. Considering FRC's enhancements from previous applications, a case study based on the Metrorrey Line 2 light-train viaduct (Mexico) is developed. The case study aims to assess the structural performance that FRC can deliver within bridge geometries, loads, and specific conditions. Two numerical models considering different transversal post-tensioning configurations are developed based on the reference structure. The use of these two numerical models aims to broaden the applicability of this study to most U-shaped light-train viaducts. The design is based on current and future standards and recommendations, being prEN1992-1-1:2021, EN1992-1-1:2004, and fib Model Code 2010. After the numerical models and structural analysis, different sectional analyses at ultimate and serviceability levels are carried out, considering both conventional and fiber reinforced concretes. From the sectional results, FRC can provide reductions to reinforcement quantities at ultimate load levels, which are tied to the initially required reinforcement ratio (in other words, linked to the internal forces existing in the element). When higher reinforcement ratios are necessary, FRC optimizations point toward serviceability limit states, especially on the crack width reduction and the potential to reduce or suppress any additional reinforcement due to crack limitations. The first author would like to acknowledge the funding support provided by the Spanish Ministry of Universities through the Ph.D. grant program Formación de Profesorado Universitario (FPU18/06067). The authors are indebted to the Spanish Ministry of Sience and Innovation for the funding provided through the research project PID2021-126405OB-C31 and to the Secretaria d’ Universitats i Recerca de la Generalitat de Catalunya, Catalunya, Spain, for the funding provided through Agaur (2017 SGR 1482).

Large number of studies analyzed physical and mechanical properties of high-volume fly ash concrete, but only a few discussed its structural behavior. Material properties are an important input parameter for structural analysis, but they are insufficient for reliable conclusions to be made. This study analyses flexural behavior of reinforced concrete beams made with 63% of low-calcium class F fly ash in total cementitious materials mass, using experimental method and analyzing current code predictions (EN 1992-1-1). The analysis was done by comparing beams made with two longitudinal reinforcement ratios, made with traditional cement concrete (OPC) and high-volume fly ash concrete (HVFAC), both corresponding to concrete class C30/37. Beams were tested in a four-point bending test measuring vertical displacement, crack development, concrete strains and longitudinal reinforcement strains. According to this research, the flexural performance of HVFAC beams is similar to flexural performance of corresponding OPC beams in terms of ultimate bending capacity. The significant difference was noticed regarding cracking extent that was higher in HVFAC beams. Available ultimate bending moments code predictions can be applied on HVFAC beams with similar precision and variation of results, like for OPC beams. However, this cannot be concluded for parameters depending on the cracking behaviour, like cracking moments or deflections. Results and analysis presented in this study indicate that HVFAC can be used in structural elements subjected dominantly to bending, like beams and slabs. More research regarding structural behavior of HVFAC using full-scale long-term tests is needed to develop larger database for reliability analysis. This work was supported by the Ministry for Education, Science and Technology, Republic of Serbia [Grant No TR36017]

Distributed Optical Fiber Sensors (DOFS) are novel and increasingly popular strain monitoring tools recently applied to the Structural Health Monitoring (SHM) of Reinforced Concrete (RC) structures. Up to now, most applications have seen the instrumenting of the latter’s external surfaces yet, in few circumstances, this technique has also been adopted with the scope of measuring the strains present on the embedded reinforcement bars (rebars). Before the advent of DOFS, due to the lack of tools able to perform such investigation in an accurate, completely-distributed and un-intrusive fashion, structural analyses that rely on the knowledge of the rebars’ strains (such as tension stiffening) have always resorted to theoretical, empirical or numerical solutions. Yet, with the potential provided by DOFS, such insight is finally acquirable and represents the start of a new way of understanding the composite behavior of RC structures. The experimental campaign, topic of the present article, intends on taking full advantage of such potential to study the bond stress and slip present on the surface between concrete and steel rebars in differently sized cracking and non-cracking RC tensile members. These are key parameters for the development of any stress transfer approach-based RC structures’ serviceability analysis, thus the importance of using DOFS for this novel application. The DOFS extracted bond/slip laws are further compared with the Model Code 2010’s predictions and seems to provide consistently higher bond stresses per similar slip than the latter. The study was performed within project No. 09.3.3-LMT-K-712-01-0145 that has received funding from European Social Fund under grant agreement with the Research Council of Lithuania (LMTLT). Furthermore, the authors acknowledge the help of COTCA Asistencia Técnica, Patología y Control de Calidad for the contribution provided in lending the OBR ODiSI-A machine.

The following paper deals with active control implementation in cable-stayed bridges. Recent developments in structural active control of cable-stayed bridges are focused on the adaptability to dynamic effects produced by earthquakes or extreme winds (El Ouni et al., 2012; Pakos and Wojcicki, 2014; Domaneschi et al., 2015a,b). Nevertheless, no attention has been paid to the static or quasi-static case. As stated by Housner et al. (1996), Song et al. (2006) or Gilewski and Al Sabouni-Zawadzka (2015), active control could also be useful to diminish fatigue in the day-to-day performance of this type of bridges by decreasing stresses adaptively. Indeed, the following paper shows that excitation periods produced by traffic loads and natural periods of vibration of this type of bridges are sufficiently distant one another so as to conclude that a quasi-static analysis can be performed. Filling this gap, the following paper proposes a structural analysis procedure to include active control systems in the design process of cable stayed bridges, as well as suggestions which ought to be considered in order to include these cases into codes. The results of the paper, studying both non-cumulative and cumulative load cases, show a reduction in unbalanced bending moment referred to the Neutral Moment State of around 25%, depending on the load case. As a result, active control systems compensating quasi-static loading patterns can certainly help engineers optimise the design of these emblematic structures.