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

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

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

Erratum to: Textile Reinforced Concrete: experimental investigation on design parameters

Textile Reinforced Concrete (TRC) is an advanced cement-based material in which fabrics used as reinforcement can bring significant loads in tension, allowing architects and engineers to use thin cross-sections. Previous research projects, developed during the last 10 years mainly in Germany, Israel and the USA, have shown the capabilities of such a material. In this paper an extensive experimental investigation of TRC is presented: tensile tests were carried out to obtain a complete mechanical characterization of the composite material under standard conditions, considering the influence of different variables such as reinforcement ratio, fabric geometry, curing conditions, displacement rate and specimen size. ******* Due to an unfortunate turn of events this article was published with wrong citations in the text to the references at the end of the article. In order to provide the correct information this article is hereafter published in its entirety with the correct citations and should be regarded as the final version by the reader

The spectral element method as an effective tool for solving large scale dynamic soil-structure interaction problems

The spectral element method (SEM) is a powerful numerical technique naturally suited for wave propagation and dynamic soil-structure interaction (DSSI) analyses. A class of SEM has been widely used in the seismological field (local or global seismology) thanks to its capability of providing high accuracy and allowing the implementation of optimized parallel algorithms. We illustrate inthis contribution how the SEM can be effectively used also for the numerical analysis of DSSI problems, with reference to the 3D seismic response of a railway viaduct in Italy. This numerical analysis includes the combined effect of: a) strong lateral variations of soil properties; b) topographic amplification; c) DSSI; d) spatial variation of earthquake ground motion in the structural response. Some hints on the work in progress to effectively handle nonlinear problems with SEM are also given

Robustness assessment of half-joint RC girder bridges

Considerable research efforts have been dedicated to understanding the resistance of buildings against progressive collapse. However, these efforts have been relatively limited in the context of bridges, despite the equal, if not more, critical importance of robustness criteria in bridge engineering. In the context of existing bridges, it is crucial not only to assess safety, but also to evaluate robustness using reliable metrics. These metrics can aid managing authorities in prioritizing necessary interventions. Considering this, the paper applies various robustness measures to a specific type of reinforced concrete (RC) girder bridge known as half-joint bridges. As a case study, the Annone viaduct is examined, which collapsed in 2016 due to the passage of a heavy truck. A notional removal approach of critical elements to quantify structural robustness is proposed. This approach considers several load configurations, some envisioned during the design stage, and others representing abnormal loads. The study results reveal specific scenarios that may lead to potential progressive collapse and highlight the preferred metrics for this type of bridges. Ultimately, the assessment of robustness can play a key role in choosing a retrofitting solution over other intervention options for existing bridges

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

Biaxial bending of SFRC slabs: Is conventional reinforcement necessary?

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