Modelling FRC infrastructures taking into account the soil-structure interaction

The favourable effect that fibres provide at concrete crack initiation and propagation is especially notable in structures of high redundant supports, such is the case of concrete infrastructures surrounded by soil. If the design of these concrete structures is governed by crack width restrictions, fibre reinforced concrete is even a more competitive solution, since the stress redistribution provided by fibres bridging the micro-cracks allows the formation of diffuse crack patterns of reduced crack width. If these structures are precast with high strength concrete, and composed by thin walled components, fibres can effectively replace the total conventional transversal reinforcement, as well as a significant percentage of flexural reinforcement, resulting high competitive structures in economic and functional terms. However, to assess the fibre reinforcement benefits in this type of engineering problems, the concrete post-cracking behaviour and the soil-structure interaction behaviour need to be modelled as accurately as possible. In this paper, a FEM-based model is briefly developed and applied to boxculvert structures. The model is described and a preliminary application is analysed. The main results are presented and discussed

CREEP OF CRACKED POLYMER FIBER REINFORCED CONCRETE UNDER SUSTAINED TENSILE LOADING

In fiber reinforced concrete (FRC), fibers are added to the fresh concrete mix in order to improve the residual tensile strength, the toughness and/or durability of a concrete element. Cur- rently, structural applications remain relatively scarce as the time-dependent behavior of FRC is still poorly understood. This paper reports the first results of an experimental campaign regarding the creep of cracked polymer FRC. In the test setup, cylindrical, notched FRC specimens are considered. The concrete is reinforced with structural polymeric fibers for use in load-bearing applications. In a first step, the material is characterized according to the European Standard EN14651. Secondly, the samples are precracked to localize the creep deformations and to monitor the crack growth in time. The samples are subjected to a sustained tensile load, whereby different load levels with respect to the individual residual strength are considered. The results of the first months of creep loading will be detailed and discussed in the paper

Dynamic behaviour of HPFRCC: The influence of fibres dispersion

The promise of fibre-reinforced cementitious composites for dynamic loading application stems from their observed good response under static loading mainly due to fibre contribution. An experimental research aimed at contributing to the understanding of the behaviour of advanced fibre-reinforced cementitious composites subjected to low and high strain rates was carried out underlining the influence of fibres. The material behaviour was investigated at three strain rates (0.1, 1, and 150 s−1) and the tests results were compared with their static behaviour. Tests at intermediate strain rates (0.1–1 s −1) were carried out by means of a hydro-pneumatic machine (HPM), while high strain rates (150 s−1) were investigated by exploiting a modified Hopkinson bar (MHB). Particular attention has been placed on the influence of fibre and fibre dispersion on the dynamic behaviour of the materials: matrix, HPFRCC with random fibre distribution and aligned fibres were compared. The comparison between static and dynamic tests highlighted several relevant aspects regarding the influence of fibres on the peak strength and post-peak behaviour at high strain rate

Robustness of RC girder bridges: The case of half-joint bridges

Considerable research efforts have been made on the progressive collapse resistance of buildings. This effort is much more limited in the case of bridges, where robustness criteria are just as, or even more important than in buildings. Existing studies dealing with the robustness of bridges, although appreciable, often are limited to qualitative considerations that can provide designers with valuable pointers when designing new bridges. It is equally important to assess not only the safety but also the robustness of existing bridges through reliable metrics that can be used in the prioritization of interventions by the managing authority. According to this aim, this paper applies a selected measure of robustness to a particular type of reinforced concrete (RC) girder bridge, namely half-joint bridges. The Annone viaduct, which collapsed in 2016 after the passage of a heavy truck, is used as a case study

Correction to: Biaxial bending of SFRC slabs: Is conventional reinforcement necessary?

The article "Biaxial bending of SFRC slabs: Is conventional reinforcement necessary?", written by Marco di Prisco, Matteo Colombo and Ali Pourzarabi, was originally published electronically on the publisher's Internet portal (currently SpringerLink) on 22 December 2018 without open access

Biaxial bending of SFRC slabs: Is conventional reinforcement necessary?

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TRC SANDWICH SOLUTION FOR ENERGY RETROFITTING

Concerning energy improvement of existing façades, a favourable system involves prefabricated multilayer panels, made of internal insulation core and outer textile reinforced concrete layers. It is a convincing alternative to external thermal insulation composite systems (ETICS) and ventilated façades, and it meets all the requirements for façade systems. The main advantage is the possibility to apply the panel using a crane, without any scaffolding. The paper considers two solutions: the former uses expanded polystyrene (EPS) as insulating material; the latter substitutes EPS with an innovative green insulation material made of inorganic diatomite. The paper aims at comparing the solutions in terms of mechanical properties of the components and behaviour of the composite sandwich at lab-scale level. Numerical models, previously calibrated, will be instrumental for the discussion

TRC sandwich solution for energy retrofitting

Concerning energy improvement of existing façades, a favourable system involves prefabricated multilayer panels, made of internal insulation core and outer textile reinforced concrete layers. It is a convincing alternative to external thermal insulation composite systems (ETICS) and ventilated façades, and it meets all the requirements for façade systems. The main advantage is the possibility toapply the panel using a crane, without any scaffolding. The paper considers two solutions: the former uses expanded polystyrene (EPS) as insulating material; the latter substitutes EPS with an innovative green insulation material made of inorganic diatomite. The paper aims at comparing the solutions in terms of mechanical properties of the components and behaviour of the composite sandwich at lab-scale level. Numerical models, previously calibrated, will be instrumental for the discussion

Effect of Textile Characteristics on the AR-Glass Fabric Efficiency

Alkali-resistant (AR) glass textiles are used as the main reinforcement in several composite applications due to their good performance-to-cost ratio. A huge variety of textiles are already present in the market; they differ on various parameters, such as, for example, the filaments’ diameters, the geometry, the type of weaving, or the nature of the impregnation coating. To orient manufacturers towards the production of efficient textiles, the most important aspect is the balance between cost and performance. In this paper, a series of different fabrics designed for textile-reinforced cementitious composites were considered. Performance was assessed by means of uniaxial tensile tests and the results are presented in terms of load vs. displacement. Then, the selected AR-glass textiles were compared in terms of fabric efficiency, targeting the effect of each parameter on the textile capacity. The research here presented is part of a comprehensive campaign aimed at the optimization of glass-fabric-reinforced cementitious composites for structural retrofitting. To better discuss the different solutions tested, at the end, only considering a small number of the investigated textiles, an efficiency evaluation was carried out at the cementitious composite level