Wireless-based identification and model updating of a skewed highway bridge for structural health monitoring

Vibration-based monitoring was performed on a short-span skewed highway bridge on the basis of wireless measurements. By means of operational modal analysis, highly accurate modal results (frequencies and mode shapes) were extracted by using a self-developed wireless acquisition system, for which the performance was verified in the field. In order to reproduce the experimental modal characteristics, a refined finite element model was manually tuned to reduce the idealization errors and then updated with the sensitivity method to reduce the parametric errors. It was found that to build a reliable Finite element (FE) model for application in structural health monitoring, the effects of superelevation and boundary conditions of a skewed bridge should be taken into account carefully

Experimental characterisation of dynamic properties of an all-FRP truss bridge

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordFibre Reinforced Polymers (FRPs) have increasingly been utilised for construction of pedestrian bridges due to high strength- and stiffness-to-weight ratios, low maintenance costs and quick installation. Their relatively low mass and stiffness make these bridges potentially susceptible to vibration serviceability problems, which increasingly govern the design. Currently, the wider application of FRPs in civil engineering is hindered by the lack of experimental insight in dynamic performance of as-built structures. This paper presents an experimental investigation on a 25, m long glass-FRP truss footbridge in Italy. Ambient vibration tests were conducted to identify the dynamic properties. The peak-picking method and stochastic subspace identification approach were employed for modal parameter identification. The two methods produced very consistent results. Eight vibration modes were identified in the frequency range up to 10, Hz. Two lateral flexural vibration modes having natural frequencies of 5.8 and 9.6, Hz were identified, as well as two vertical flexural modes (at 7.5 and 8.1, Hz) and four torsional modes (at 2.1, 2.7, 4.8 and 9.3, Hz). Damping ratios for all modes up to 10, Hz except the eighth mode were above 1.2%.Engineering and Physical Sciences Research Council (EPSRC

Bulk Mediated Surface Diffusion: Non Markovian Desorption with Finite First Moment

Here we address a fundamental issue in surface physics: the dynamics of adsorbed molecules. We study this problem when the particle's desorption is characterized by a non Markovian process, while the particle's adsorption and its motion in the bulk are governed by a Markovian dynamics. We study the diffusion of particles in a semi-infinite cubic lattice, and focus on the effective diffusion process at the interface $z = 1$. We calculate analytically the conditional probability to find the particle on the $z=1$ plane as well as the surface dispersion as functions of time. The comparison of these results with Monte Carlo simulations show an excellent agreement.Comment: 16 pages, 7 figs. European Physical Journal B (in press

Urinary Sodium Profiling in Chronic Heart Failure to Detect Development of Acute Decompensated Heart Failure

OBJECTIVES This study sought to determine the relationship between urinary sodium (U-na) concentration and the pathophysiologic interaction with the development of acute heart failure (AHF) hospitalization. BACKGROUND No data are available on the longitudinal dynamics of U-na concentration in patients with chronic heart failure (HF), including its temporal relationship with AHF hospitalization. METHODS Stable, chronic HF patients with either reduced or preserved ejection fraction were prospectively included to undergo prospective collection of morning spot U-na samples for 30 consecutive weeks. Linear mixed modeling was used to assess the longitudinal changes in U-na concentration. Patients were followed for the development of the clinical endpoint of AHF. RESULTS A total of 80 chronic HF patients (71 +/- 11 years of age; an N-terminal pro-B-type natriuretic peptide [NT-proBNP] concentration of 771 [interquartile range: 221 to 1,906] ng/l; left ventricular ejection fraction [LVEF] 33 +/- 7%) prospectively submitted weekly pre-diuretic first void morning U-na samples for 30 weeks. A total of 1,970 U-na samples were collected, with mean U-na concentration of 81.6 +/- 41 mmol/l. Sodium excretion remained stable over time on a population level (time effect p = 0.663). However, interindividual differences revealed the presence of high (88 mmol/l U-na [n = 39]) and low (73 mmol/l U-na [n = 41]) sodium excreters. Only younger age was an independent predictor of high sodium excretion (odds ratio [OR]: 0.91; 95% confidence interval [CI]: 0.83 to 1.00; p = 0.045 per year). During 587 +/- 54 days of follow-up, 21 patients were admitted for AHF. Patients who developed AHF had significantly lower U-na concentrations (F-[1.80] = 24.063; p <0.001). The discriminating capacity of U-na concentration to detect AHF persisted after inclusion of NT-proBNP and estimated glomerular filtration rate (eGFR) measurements as random effects (p = 0.041). Furthermore, U-na concentration dropped (U-na = 46 +/- 16 mmol/l vs. 70 +/- 32 mmol/l, respectively; p = 0.003) in the week preceding the hospitalization and returned to the individual's baseline (U-na = 71 +/- 22 mmol/l; p = 0.002) following recompensation, while such early longitudinal changes in weight and dyspnea scores were not apparent in the week preceding decompensation. CONCLUSIONS Overall, U-na concentration remained relatively stable over time, but large interindividual differences existed in stable, chronic HF patients. Patients who developed AHF exhibited a chronically lower U-na concentration and exhibited a further drop in U-na concentration during the week preceding hospitalization. Ambulatory U-na sample collection is feasible and may offer additional prognostic and therapeutic information. (C) 2019 by the American College of Cardiology Foundation

Selective abdominal venous congestion induces adverse renal and hepatic morphological and functional alterations despite a preserved cardiac function

Venous congestion is an important contributor to worsening renal function in heart failure and the cardiorenal syndrome. In patients, it is difficult to study the effects of isolated venous congestion on organ function. In this study, the consequences of isolated abdominal venous congestion on morphology and function of the kidneys, liver and heart were studied in a rat model. Twelve shamoperated (SHAM) male Sprague Dawley rats were compared to eleven inferior vena cava-constricted (IVCc) rats for twenty-one weeks. Abdominal venous pressure was significantly higher in the IVCc versus SHAM group (p < 0.0001). Indices of liver and kidney weight, function and morphology, inflammation as well as collagen deposition were significantly increased in the IVCc compared to SHAM group, (p < 0.05). Echocardiographic and hemodynamic parameters were largely unaffected by abdominal venous congestion. In this rat model of isolated abdominal venous congestion, retrogradely conducted glomerular hypertension without a concomitant change in glomerular filtration rate was observed. Adverse short-term hepatic morphological alterations were developed which explain the observed organ function dysfunction. Importantly, cardiac function remained comparable between both groups. This study provides relevant insight in the pathophysiology of abdominal congestion on organ function

Dynamics of viscoelastic membranes

We determine both the in-plane and out-of-plane dynamics of viscoelastic membranes separating two viscous fluids in order to understand microrheological studies of such membranes. We demonstrate the general viscoelastic signatures in the dynamics of shear, bending, and compression modes. We also find a screening of the otherwise two-dimensional character of the response to point forces due to the presence of solvent. Finally, we show that there is a linear, hydrodynamic coupling between the in-plane compression modes of the membrane and the out-of-plane bending modes in the case where the membrane separates two different fluids or environments

Some advances in extensive bridge monitoring using low cost dynamic characterization

Dynamic measurements will become a standard for bridge monitoring in the near future. This fact will produce an important cost reduction for maintenance. US Administration has a long term intensive research program in order to diminish the estimated current maintenance cost of US$7 billion per year over 20 years. An optimal intervention maintenance program demands a historical dynamical record, as well as an updated mathematical model of the structure to be monitored. In case that a model of the structure is not actually available it is possible to produce it, however this possibility does not exist for missing measurement records from the past. Current acquisition systems to monitor structures can be made more efficient by introducing the following improvements, under development in the Spanish research Project “Low cost bridge health monitoring by ambient vibration tests using wireless sensors”: (a) a complete wireless system to acquire sensor data, (b) a wireless system that permits the localization and the hardware identification of the whole sensor system. The applied localization system has been object of a recent patent, and (c) automatization of the modal identification process, aimed to diminish human intervention. This system is assembled with cheap components and allows the simultaneous use of a large number of sensors at a low placement cost. The engineer’s intervention is limited to the selection of sensor positions, probably based on a preliminary FE analysis. In case of multiple setups, also the position of a number of fixed reference sensors has to be decided. The wireless localization system will obtain the exact coordinates of all these sensors positions. When the selection of optimal positions is difficult, for example because of the lack of a proper FE model, this can be compensated by using a higher number of measuring (also reference) points. The described low cost acquisition system allows the responsible bridge administration to obtain historical dynamic identification records at reasonable costs that will be used in future maintenance programs. Therefore, due to the importance of the baseline monitoring record of a new bridge, a monitoring test just after its construction should be highly recommended, if not compulsory

Prospects for the Improvement of Energy Performance in Agroindustry Using Phase Change Materials

This work was partially supported by the Fundação para a Ciência e Tecnologia, UIDB/00066/2020 (CTS – Center of Technology and Systems).The use of Phase Change Materials (PCMs), able to store latent heat, represents an opportunity to improve energy efficiency in the agroindustry by means of thermal energy storage. PCMs provide higher energy density then sensible heat storage mediums, thus paving the way to multiple applications, like supporting the integration of renewables or allowing for new storage architectures, decentralized and directly installed in the chain production equipment, creating e.g. the opportunity to recover and value low-grade operational heat sub-products. Such new and decentralized architecture, not currently applied in agroindustry, is proposed in this work. A chocolate tempering machine using an organic PCM is conceived and analyzed using ANSYS Fluent software for computational fluid dynamics simulations, comparing the main aspects in the storage capacity and discharging process with a conventional sensitive heat storage solution that uses water. PCMs allows improving the stored energy, keeping the chocolate in the working temperature after being tempered for more than four times longer than using only hot water. If the PCMs are charged by renewables, the self-consumption ratio can be improved while providing energy flexibility to the user.authorsversionpublishe