Assessment of fire damage in concrete structures: new inspection tools and combined interpretation of results

The assessment of fire damage in concrete structures involves two complementary major tasks: on-site investigation and interpretation of the observed evidences. Concerning the first point, some innovative and viable inspection techniques are briefly illustrated in the paper. Their common trait is the ability to provide an immediate feedback, with no need for time-consuming laboratory analyses. As for the interpretation of results, the main issue is to harmonize the information provided by the available diagnostic tools, which is limited to specific ranges of temperature and to definite depths in the exposed concrete cover. The proposed approach relies on the parametric analysis of the compartment temperature developed in a set of realistic fire scenarios. The resulting temperature profiles are then checked against the results of the Non-Destructive inspection techniques, in order to select the most likely thermal input undergone by the structural members

Combined while-drilling techniques for the assessment of deteriorated concrete cover

In this paper the idea of monitoring the resistance encountered while taking a sample from a concrete structure and to combine this data with the analysis of the extracted material has been regarded as a method for detecting the possible deterioration of the concrete cover. In the common case of core drilling, the time spent for a unit penetration proved to be a good indicator of the local material response. Hence, the laboratory analyses can be easily integrated with this preliminary scan of the material quality, which comes at no cost once the acquisition of samples has been planned. On the other hand, hammer-drilling of small holes is a definitely faster and less invasive alternative for inspecting the mechanical response at increasing depth within the cover. Although this method is not intended to provide a material sample, the analysis of the ground-concrete powder and the visual inspection of the remaining hole proved to be a viable alternative to the traditional examination of cores

Pulse-Echo Monitoring of Concrete Damage and Spalling during Fire

Monitoring concrete damage and spalling progression in structural members during fire tests (hot conditions) is a central but challenging task, since the high temperatures involved make difficult the implementation of most of the common Non- Destructive evaluation methods. Hence, an advanced ultrasonic technique – Ultrasonic Pulse-Echo (UPE) – was recently adapted for real time survey in fire test, in order to evaluate the material damage during heating. The UPE technique was implemented at the cold (upper) face of concrete slabs (800x800x100 mm) heated at the bottom face according to the Standard Fire and subjected to biaxial compressive membrane loading. Different concretes were tested, with grades ranging from 40 to 60 MPa, with and without different kinds of fibre (monofilament or fibrillated polypropylene, or steel fibres). Furthermore, different load levels were applied, from 0 to 25% of the original compressive strength. During tests, spalling was generally observed in loaded plain concrete (up to 50-60 mm depth), while only slight scaling was experienced on unloaded samples or if polypropylene fibre was added. The method proved to be very effective in recognizing the decay of the Ultrasonic Pulse Velocity (UPV) with temperature and the role played by external loading and fibre type

Digital business models in cultural tourism

Purpose Digitalization had a relevant impact on the cultural tourism sector, both demand and supply. If, on the one hand, advances in digital technologies provided tourists with new mobile services able to amplify the cultural experience, on the other hand, they catalyzed the development of new business models by digital enterprises. This paper has a twofold purpose: to detect business models and key characteristics of mobile apps for cultural tourism and to analyze the offering of app-based services in this sector. Design/methodology/approach The authors defined a methodology to identify, characterize and analyze a particular category of digital products for cultural tourism: app-based services. They are studied in terms of value creation, proposition and capture with the aim to identify the distinctive features of business models. As a result, the authors identified a classification framework on three main dimensions, namely "how to exploit mobile app features to create value for cultural tourists" (value creation), "which valuable services are delivered to cultural tourists" (value proposition) and "how companies are rewarded for the value they offered" (value capture). The authors apply the framework to perform a situation analysis of app-based services in the cultural tourism market. Findings The analysis highlights that digital enterprises offering app-based services do not fully exploit advances in technologies about users' value requirements. Hence, the results of our work suggest some directions that digital enterprises may follow to better exploit mobile app technology. Originality/value To date, little research has been devoted to investigating cultural tourism business models involving the exploitation of mobile app-based services. This research provides a useful framework to analyze fundamental aspects of business models in this sector. Such a framework represents a practical tool that provides fruitful insights for the design of a new generation of app-based services within the so-called "Internet of things" domain

Beyond mean-field bistability in driven-dissipative lattices: bunching-antibunching transition and quantum simulation

In the present work we investigate the existence of multiple nonequilibrium steady states in a coherently driven XY lattice of dissipative two-level systems. A commonly used mean-field ansatz, in which spatial correlations are neglected, predicts a bistable behavior with a sharp shift between low- and high-density states. In contrast one-dimensional matrix product methods reveal these effects to be artifacts of the mean-field approach, with both disappearing once correlations are taken fully into account. Instead, a bunching-antibunching transition emerges. This indicates that alternative approaches should be considered for higher spatial dimensions, where classical simulations are currently infeasible. Thus we propose a circuit QED quantum simulator implementable with current technology to enable an experimental investigation of the model considered

Photon transfer in ultrastrongly coupled three-cavity arrays

We study the photon transfer along a linear array of three coupled cavities where the central one contains an interacting two-level system in the strong and ultrastrong coupling regimes. We find that an inhomogeneously coupled array forbids a complete single-photon transfer between the external cavities when the central one performs a Jaynes-Cummings dynamics. This is not the case in the ultrastrong coupling regime, where the system exhibits singularities in the photon transfer time as a function of the cavity-qubit coupling strength. Our model can be implemented within the state-of-the-art circuit quantum electrodynamics technology and it represents a building block for studying photon state transfer through scalable cavity arrays.Comment: 5 pages, 5 figures, supplemental materia

Critical parametric quantum sensing

Critical quantum systems are a promising resource for quantum metrology applications, due to the diverging susceptibility developed in proximity of phase transitions. Here, we assess the metrological power of parametric Kerr resonators undergoing driven-dissipative phase transitions. We fully characterize the quantum Fisher information for frequency estimation, and the Helstrom bound for frequency discrimination. By going beyond the asymptotic regime, we show that the Heisenberg precision can be achieved with experimentally reachable parameters. We design protocols that exploit the critical behavior of nonlinear resonators to enhance the precision of quantum magnetometers and the fidelity of superconducting qubit readout.Comment: 6 pages + Supplemental Material, 4 figure

Experimental Study on the Explosive Spalling in High-Performance Concrete: Role of Aggregate and Fiber Types

A complete description of the mechanical behavior of High-Performance Concrete in fire still requires further efforts to fully understand the tricky phenomenon of spalling, whose complexity comes from the interaction among different phenomena, namely: the microstructural changes occurring in concrete at high temperature, the pressure rising in the pores, and the stress induced by both thermal gradients and external loads. To what extent these different aspects influence each other is still not completely clear, and within this context a comprehensive experimental campaign has been launched at the Politecnico di Milano, focusing on the role played by concrete grade, aggregate type, and fiber type and content. Eleven concrete mixes are investigated considering three grades (fc ≥ 40, 60 and 90 MPa), three aggregate types (silico-calcareous, basalt and calcareous aggregates) and different fiber types and contents (steel and monofilament or fibrillated polypropylene fibers)