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Knowledge of the behavior of concrete at mesoscale level requires, as a fundamental aspect, to characterize aggregates and specifically, their thermal properties if fire hazards (e.g. spalling) are accounted for. The assessment of aggregates performance (and, correspondingly, concrete materials made of aggregates, cement paste and ITZ – interfacial transition zone) is crucial for defining a realistic structural response as well as damage scenarios.

It is here assumed that concrete creep is associated to cement paste only and that creep obeys to the B3 model proposed by Bažant and Baweja since it shows good compatibility with experimental results and it is properly justified theoretically.

First, the three‐dimensionality of the geometric description of concrete at the meso‐level can be appreciated; then, creep of cement paste and ITZ allows to incorporate in the model the complex reality of creep, which is not only a matter of fluid flow and pressure dissipation but also the result of chemical‐physical reactions; again, the description of concrete as a composite material, in connection with porous media analysis, allows for understanding the hygro‐thermal and mechanical response of concrete, e.g. hygral barriers due to the presence of aggregates can be seen only at this modelling level. Finally, from the mechanical viewpoint, the remarkable damage peak effect arising from the inclusion of ITZ, if compared with the less pronounced peak when ITZ is disregarded from the analysis, is reported.

The fully coupled 3D F.E. code NEWCON3D has been adopted to perform fully coupled thermo‐hygro‐mechanical meso‐scale analyses of concrete characterized by aggregates of various types and various thermal properties. The 3D approach allows for differentiating each constituent (cement paste, aggregate and ITZ), even from the point of view of their rheologic behaviour. Additionally, model B3 has been upgraded by the calculation of the effective humidity state when evaluating drying creep, instead than using approximate expressions. Damage maps allows for defining an appropriate concrete mixture to withstand spalling and to characterize the coupled behaviour of ITZ as well.

This paper aims to propose a methodology to remove inherent implicit creep from the Eurocode 3 material model for steel and to present a creep-free analysis on simply supported steel members.

Most of the available material models of steel are based on transient coupon tests, which inherently include creep strain associated with particular heating rates and load ratios.

The creep-free analysis aims to reveal the influence of implicit creep by investigating the behaviour of simply supported steel beams and columns exposed to various heating regimes. The paper further evaluates the implicit consideration of creep in the Eurocode 3 steel material model.

A modified Eurocode 3 carbon steel material model for creep-free analysis is proposed for general structural fire engineering analysis.

A non-linear creep function embedded in an elastic visco-plastic (EVP) model can simulate the decrease of creep compression rate with time. It overcomes the limitation of a linear logarithmic creep function, by which creep continuously increases to infinite value as time approaches infinity. However, the determination of the creep model parameters is a challenging task to apply the EVP model. Therefore, this paper presents a new numerical solution to determine the EVP model parameters applying trust-region reflective least square optimisation algorithm and the finite difference scheme to simulate stress-strain behaviour of soft soil.

In this paper, the developed method is verified against the field case study of Väsby test fill. A set of EVP model parameters is obtained by applying the developed method to the available laboratory consolidation results of Väsby clay. Then, the predictions of settlement and the excess pore water pressure at different depths are compared to the available field measurement.

The analysis results show the developed method is a reliable tool to evaluate the long-term performance of soft soils under embankments.

Practicing engineers can use the proposed optimisation algorithm to increase the accuracy of the soil visco-plastic model parameters by utilising all laboratory results of several loading stages during and after the dissipation of the excess pore water pressure.

A novel numerical solution to determine the viscoplastic model parameters applying trust-region reflective least square optimisation algorithm has been developed.

The purpose of this paper is to derive the exact analytical expressions for torsion and bending creep of rods with the Norton-Bailey, Garofalo and Naumenko-Altenbach-Gorash constitutive models. These simple constitutive models, for example, the time- and strain-hardening constitutive equations, were based on adaptations for time-varying stress of equally simple models for the secondary creep stage from constant load/stress uniaxial tests where minimum creep rate is constant. The analytical solution is studied for Norton-Bailey and Garofalo laws in uniaxial states of stress.

The creep component of strain rate is defined by material-specific creep law. In this paper the authors adopt, following the common procedure Betten, an isotropic stress function. The paper derives the expressions for strain rate for uniaxial and shear stress states for the definite representations of stress function. First, in this paper the authors investigate the creep for the total deformation that remains constant in time.

The exact analytical expressions giving the torque and bending moment as a function of the time were derived.

The material isotropy and homogeneity preimposed. The secondary creep phase is considered.

The results of creep simulation are applied to practically important problem of engineering, namely for simulation of creep and relaxation of helical and disk springs.

The new, closed form solutions with commonly accepted creep models allow a deeper understanding of such a constitutive model's effect on stress and deformation and the implications for high temperature design. The application of the original solutions allows accurate analytic description of creep and relaxation of practically important problems in mechanical engineering. Following the procedure the paper establishes closed form solutions for creep and relaxation in helical, leaf and disk springs.

Creep behavior of concrete at high temperature has become a major concern in building structures, such as factories, bridges, tunnels, airports and nuclear buildings. Therefore, a simple and accurate prediction model for the high-temperature creep behavior of concrete is crucial in engineering applications.

In this paper, the variable-order fractional operator is introduced to capture the high-temperature creep behavior of concrete. By assuming that the variable-order function is a linear function with time, the proposed model benefits from the advantages of both formal simplicity and the physical significance for macroscopic intermediate materials. The effectiveness of the model is demonstrated by data fitting with existing experimental results of high-temperature creep of two representative concretes.

The results show that the proposed model fits well with the experimental data, and the value of order is increasing with the increase of the applied stress levels, which meets the fact that higher stress can accelerate the rate of creep. Furthermore, the relationship between the model parameters and loading conditions is deeply analyzed. It is found that the material coefficients are constant at a constant temperature, while the order function parameters are determined by the applied stress levels. Finally, the variable-order fractional model can be further written into a general equation of time and applied stress.

This paper provides a simple and practical variable-order fractional model for predicting the creep behavior of concrete at high temperature.

In this addendum, the purpose of this paper is to introduce the new creep law for the description of the different stages of creep. The introduced creep law generalizes the creep law used in Kobelev (2014).

The new generalized creep law demonstrates the relationship between creep rate and stress as well as accounts the time dependence in different creep regimes. In the stage of primary creep there is explicit time dependence of creep rate. In the stage of secondary creep the creep rate exhibits – analogously to the original creep law – no explicit dependence on time.

The closed form expressions giving the torque and bending moment as a function of the time are provided. The method is applicable for definite other stress functions in the creep law.

The arbitrary creep law allows the separation of time and spatial variables; exponential and power-law time dependence.

The results of creep simulation are applied to practically important problem of engineering, namely for simulation of creep and relaxation of helical and disk spring, driveshafts, torque elements of machine dynamics.

The new creep model with fractional derivative of time dependence is introduced. The closed form solutions for new creep model allow simple formulas for creep effect on stress and deformation and the implications for high temperature design.

A solution algorithm for the transient analysis of bodies undergoing creep under constant or time varying loads is presented. The constitutive equation adopted is of the form: έc=γσm. The finite element formulation is carried out in terms of displacements and creep strains as internal variables. The time discretization is achieved with a trapezoidal time integration scheme. The creep strains are condensed out to give an equation for displacement increments involving a modified stiffness matrix and force vector. A Newton—Raphson iterative scheme is used for the non‐linear creep strain rate‐stress relation, and creep strains are updated at the end of the time step. The algorithm has been implemented in NOSTRUM for two‐dimensional structural and plane continuum problems, with a von Mises type potential function governing the multiaxial creep constitutive relationship. Numerical results are presented.

The purpose of the investigation was to examine the tertiary creep and the creep fracture characteristics of an aluminium alloy to specification B.S.2L42, subject to complex stressing at 200 dog. C. The scope of the work involved seven pure torsion, pure tension, and combined tension and torsion creep tests, of durations between 300 hrs. and 3,000 hrs., on the aluminium alloy at 200 deg. C., and analysis of the results.

This paper aims to develop a numerical, micromechanical model to predict the evolution of autogenous shrinkage of hydrating cement paste at early age (up to 7 days). Autogeneous shrinkage can be important in high-performance concrete characterized by low water to cement (w/c) ratios. The occurrence of this phenomenon during the first few days of hardening may result in early-age cracking in concrete structures. A good prediction of autogeneous shrinkage is necessary to achieve better understanding of the mechanisms and the deployment of effective measures to prevent early-age cracking.

Three-dimensional digital microstructures from the hydration modelling platform μic of cement paste were used to simulate macroscopic autogenous shrinkage based on the mechanism of capillary tension. Elastic and creep properties of the digital microstructures were calculated by means of finite element (FE) method homogenization. Autogenous shrinkage was then estimated as the average hydrostatic strain resulting from the capillary stress that was globally applied on the simulated digital microstructures. For this estimation, two approaches of homogenization technique, i.e. analytical poro-elasticity and numerical creep-superposition were used.

The comparisons of between the simulated and experimentally measured deformations indicate that the creep-superposition approach is more reasonable to estimate shrinkage at different water to cement ratios. It was found that better estimations could be obtained at low degrees of hydration, by assuming a loosely packed calcium silicate hydrates (C-S-H) growing in the microstructures. The simulation results show how numerical models can be used to upscale from microscopic characteristics of phases to macroscopic composite properties such as elasticity, creep and shrinkage.

While the good predictions of some cement paste properties from the microstructure at early age were obtained, the current models have several limitations that are needed to overcome in the future. Firstly, the limitation of pore-structure representation is not only from lack understanding of C-S-H structure but also from the computational complexity. Secondly, the models do not consider early-age expansion that usually happens in practice and appears to be superimposed on an underlying shrinkage as observed in experiments. Thirdly, the simplified assumptions for mechanical simulation do not accurately reflect the solid–liquid interactions in the real partially saturated system, for example, the globally applying capillary stress on the boundary of the microstructure to find the effective deformation, neglecting water flow and the pore pressure. Last but not least, the models, due to the computational complexities, use many simplifications such as FE approximation, mechanical phase properties and creep statistical data.

This study holistically tackles the phenomenon of autogeneous shrinkage through microstructural modelling. In a first such attempt, the authors have used the same microstructural model to simulate the microstructural development, elastic properties, creep and autogeneous shrinkage. The task of putting these models together was not simple. The authors have successfully handled several problems at each step in an elegant manner. For example, although several earlier studies have pointed out that discrete models are unable to capture the late setting times of cements due to mesh effects, this study offers the most effective solution yet on the problem. It is also the first time that creep and shrinkage have been modelled on a young evolving microstructure that is subjected to a time variable load.

This essay examines ethical aspects of the use of facial recognition technology for surveillance purposes in public and semipublic areas, focusing particularly on the balance between security and privacy and civil liberties. As a case study, the FaceIt facial recognition engine of Identix Corporation will be analyzed, as well as its use in “Smart” video surveillance (CCTV) systems in city centers and airports. The ethical analysis will be based on a careful analysis of current facial recognition technology, of its use in Smart CCTV systems, and of the arguments used by proponents and opponents of such systems. It will be argued that Smart CCTV, which integrates video surveillance technology and biometric technology, faces ethical problems of error, function creep and privacy. In a concluding section on policy, it will be discussed whether such problems outweigh the security value of Smart CCTV in public places.