Tuned mass sampers (TMDs) are widely used strategies for vibration control in many engineering applications, so that many TMD optimization criteria have been proposed till now. However, they normally ...consider only TMD stiffness and damping as design variables and assume that the tuned mass is a pre-selected value. In this work a more complete approach is proposed and then also TMD mass ratio is optimized. A standard single degree of freedom system is investigated to evaluate TMD protection efficiency in case of excitation at the support. More precisely, this model is used to develop two different optimizations criteria which minimize the main system displacement or the inertial acceleration. Different environmental conditions described by various characterizations of the input, here modelled by a stationary filtered stochastic process, are considered. Results show that all solutions obtained considering also the mass of the TMD as design variable are more efficient if compared with those obtained without it. However, in many cases these solutions are inappropriate because the optimal TMD mass is greater than real admissible values in practical technical applications for civil and mechanical engineering. Anyway, one can deduce that there are some interesting indications for applications in some actual contexts. In fact, the results show that there are some ranges of environmental parameters ranges where results attained by the
displacement criterion are compatible with real applications requiring some percent of main system mass. Finally, the present research gives promising indications for complete TMD optimization application in emerging technical contexts, as micromechanical devices and nano resonant beams.
•A nano montmorillonite modified (MNMt) with organosilanes is investigated.•Various river sludge replacements and MNMt dosages are explored.•Cation exchange capacity is important in MNMt's ability to ...solidify heavy metals.•The introduction of MNMt facilitates hydration of the cement slag system.•MNMt fills matrix pores optimizing pore size distribution and repairing cracks.
The effect of replacing cementitious materials with different dosages of river sludge on the properties of the cement-slag binary-based geopolymer composites was investigated. The application of this research is the possibility of reusing river sludge into environment-friendly unburned bricks. The influence of nano-montmorillonite on the solidification of heavy metals in the matrix was also explored. Samples containing sludge were characterized by lower fluidity and compressive strength, but prolonged hardening time; at 60% replacement, the strength was equal to 8 MPa and the final setting time was 4.5 h. The sample including 0.4% NMt helps to improve strength thanks to its ability to partially fill the capillary pores and promote the degree of hydration. The pastes containing NMt have less dangerous heavy metals like Cu (II) and Cr (VI). The reaction products and the microstructure of the mixes with modified-NMt are exploited to understand the mechanisms at the basis of the findings.
Summary
The tuned mass damper inerter (TMDI) is an enhanced variant of the tuned mass damper (TMD) that benefits from the mass‐amplification effect of the inerter. Here, a multi‐TMDI (MTMDI) system ...(comprising more than one TMDI) linking two adjacent high‐rise buildings is presented as an unconventional seismic protection strategy. The relative acceleration response of the adjacent structures triggers large reaction forces of the inerter devices in the MTMDI, which in turn efficiently improve the seismic performance of the two buildings. By addressing a real project of two adjacent high‐rise buildings connected by two corridors equipped with the proposed MTMDI system, the displacement‐, interstory drift‐, and acceleration‐based parametric optimizations are separately performed by employing Nondominated Sorting Genetic Algorithm II (NSGA‐II) under 44 ground motions from the FEMA P695 far‐field record set. It is found that the frequency content of the seismic input has strong impact on the MTMDI mitigation performance. Adopting realistic mass ratio constraints, the optimally designed MTMDI outperforms both conventional MTMD and single TMDI in acceleration control, while it is not much effective in mitigating the displacement response due to the highly flexible nature of the high‐rise buildings, in contrast to other literature studies generally focused on low‐to‐medium rise buildings.
Firstly formulated to solve unconstrained optimization problems, the common way to solve constrained ones with the metaheuristic particle swarm optimization algorithm (PSO) is represented by adopting ...some penalty functions. In this paper, a new nonpenalty-based constraint handling approach for PSO is implemented, adopting a supervised classification machine learning method, the support vector machine (SVM). Because of its generality, constraint handling with SVM appears more adaptive both to nonlinear and discontinuous boundary. To preserve the feasibility of the population, a simple bisection algorithm is also implemented. To improve the search performances of the algorithm, a relaxation function of the constraints is also adopted. In the end part of this paper, two numerical literature benchmark examples and two structural examples are discussed. The first structural example refers to a homogeneous constant cross-section simply supported beam. The second one refers to the optimization of a plane simply supported Warren truss beam. The obtained results in terms of objective function demonstrate that this new approach represents a valid alternative to solve constrained optimization problems even in structural optimization field. Furthermore, as demonstrated by the Warren truss beam problem, this new algorithm provides an optimal structural design which represents also a good solution from the technical point of view with a trivial rounding-off that does not jeopardize significantly the optimization design process.
•Inert granite powder and active mineral admixtures were introduced to prepare sustainable manufactured sand mortar.•Inert granite powder and active mineral admixtures showed synergistic effects on ...performance of manufactured sand mortar.•Granite powder can refine the microstructure of mortar owing to the hydration promotion and the pore filling effect.•The chloride diffusion coefficient is highly correlated with capillary pore characteristics.
Granite powder (GP) and active mineral admixture including ground granulated blast furnace slag (GGBFS), metakaolin (MK) and fly ash (FA) were used to partially replace granite manufactured sand (GMS) and cement to prepare manufactured sand mortar (MSM). Synergistic effect of four mineral admixtures in MSM on mechanical properties, water absorption properties and chloride permeability was studied. Combined with the analysis of cementitious materials hydration and pore characteristics, the synergistic mechanism of four mineral admixtures was comprehensively expounded. The results show that although the synergy of GP can improve the performance of MSM, the replacement of cement by GGBFS and FA leads to the increase of water absorption and chloride diffusion coefficient and the decrease of mechanical properties. Synergistic effect of GP, GGBFS, FA and MK is greater than that of the three of them due to the complementarity of particle size and chemical composition of the four materials, which ends the situation of MSM performance reduction.
Fluid viscous dampers have been widely applied to reduce the effects of vibrations in civil engineering structures. A good understanding of the dynamical behavior of these devices is required to ...analyze structures equipped with fluid viscous dampers. The simple Kelvin–Voigt and Maxwell rheological models do not have enough parameters to suitably capture the frequency dependence of device parameters, so other models representing some generalizations of the basic Kelvin–Voigt and Maxwell models have been developed. This paper deals with parameter identification for basic and generalized Kelvin–Voigt and Maxwell models for fluid viscous dampers. The identification procedure gives the best mechanical parameters by minimizing a suitable objective function that represents a measure of difference between analytical and experimental applied forces. For this purpose, the particle swarm optimization is adopted. Results are obtained under various test conditions, comparing the agreement of various models with experimental data. Finally, a numerical investigation is performed on a simple one degree of freedom structure, equipped with fluid viscous dampers and subject to a real seismic motion.
•This work is concerned with linear piezoelectric bimorphs under random vibrations.•The base motion is modeled as modulated and filtered white Gaussian noise.•A semi-analytical procedure is developed ...for the probabilistic analysis.•Mean and standard deviation of the generated electrical energy are estimated.
This paper proposes a comprehensive method for the electromechanical probabilistic analysis of piezoelectric energy harvesters subjected to modulated and filtered white Gaussian noise (WGN) at the base. Specifically, the dynamic excitation is simulated by means of an amplitude-modulated WGN, which is filtered through the Clough-Penzien filter. The considered piezoelectric harvester is a cantilever bimorph modeled as Euler-Bernoulli beam with a concentrated mass at the free-end, and its global behavior is approximated by the fundamental vibration mode (which is tuned with the dominant frequency of the dynamic input). A resistive electrical load is considered in the circuit. Once the Lyapunov equation of the coupled electromechanical problem has been formulated, an original and efficient semi-analytical procedure is proposed to estimate mean and standard deviation of the electrical energy extracted from the piezoelectric layers.
AbstractDuring the last years, several mechanics-based macromodels have been proposed to assess the cyclic response of infilled RC frames. However, the uncertainties behind the assumptions on damage ...and failure mechanisms compromise the reliability of such approaches. For this reason, this paper proposes a new data-driven hysteresis model for the cyclic response of infilled RC frames. The infill panel is schematized as a single-degree-of-freedom element, whose constitutive law is given by the proposed hysteresis model. The model combines a degrading Bouc–Wen element with a slip-lock element, which is introduced specifically to reproduce the pinching effect due to crack openings in the masonry panel. The parameters governing the model have clear physical meanings and are calibrated on the basis of an experimental data set of cyclic responses of single-story single-bay RC infilled frames. The calibrations are carried out by means of a genetic algorithm–based optimization. Analytical correlation laws linking the model parameters with geometric and mechanical properties of the RC infilled frame are proposed and validated by blind validation tests. Results show adequate accuracy of the model in reproducing the cyclic response of infilled frames characterized by significantly different geometrical and mechanical features. The model is defined by a smooth analytical hysteresis law, with great advantages regarding numerical stability and computational effort. This makes it suitable for dynamic and stochastic simulations.
Adrenergic pathways represent the main channel of communication between the nervous system and the immune system. During inflammation, blood monocytes migrate within tissue and differentiate into ...macrophages, which polarize to M1 or M2 macrophages with tissue-damaging or -reparative properties, respectively. This study investigates whether the β-adrenergic receptor (β-AR)-blocking drug propranolol modulates the monocyte-to-macrophage differentiation process and further influences macrophages in their polarization toward M1- and M2-like phenotypes. Six-day-human monocytes were cultured with M-CSF in the presence or absence of propranolol and then activated toward an M1 pro-inflammatory state or an M2 anti-inflammatory state. The chronic exposure of monocytes to propranolol during their differentiation into macrophages promoted the increase in the M1 marker CD16 and in the M2 markers CD206 and CD163 and peroxisome proliferator-activated receptor ɣ expression. It also increased endocytosis and the release of IL-10, whereas it reduced physiological reactive oxygen species. Exposure to the pro-inflammatory conditions of propranolol-differentiated macrophages resulted in an anti-inflammatory promoting effect. At the molecular level, propranolol upregulated the expression of the oxidative stress regulators NRF2, heme oxygenase-1 and NQO1. By contributing to regulating macrophage activities, propranolol may represent a novel anti-inflammatory and immunomodulating compound with relevant therapeutic potential in several inflammatory diseases.
•Axial force-bending moment interaction diagrams for circular RC sections are derived.•A closed-form formulation is proposed for solid and hollow circular cross-sections.•A simple design procedure ...for the longitudinal reinforcement is also presented.
This paper proposes a simple closed-form approximation of the axial force-bending moment interaction diagram for solid and hollow circular reinforced concrete (RC) cross-sections with an arbitrary number of layers of longitudinal reinforcement. The implemented nonlinear material models are those of the European building code. Specifically, the parabola-rectangular strain-stress relation and the stress-block model are considered for the concrete in compression. On the other hand, the elastic-perfectly plastic behavior is assumed for the reinforcing steel bars. The proposed semi-exact closed-form approximation involves one parameter only, which is calibrated by means of a numerical optimization procedure taking into account a large database of cross-sections. Moreover, an efficient procedure is developed for the design of the outer layer of longitudinal reinforcement in solid or hollow circular RC cross-sections under combined axial force and bending moment (the mechanical ratio of any other layers of longitudinal reinforcement is considered as known function of the mechanical ratio of the outer layer of longitudinal reinforcement). Finally, several numerical examples are included to demonstrate the accuracy of the approximated axial force-bending moment interaction diagram and the effectiveness of the derived design procedure.
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