Experimental and numerical studies of inclined cables: free and parametrically-forced vibrations

Because of few experimental studies in the inclined cable literature, this paper is aimed at experimental modelling and investigating the linear free and nonlinear forced vibrations of sagged inclined cables, by discussing the relevant outcomes in the background of theoretical and numerical achievements. Attention is paid to the identification of cable hybrid modes due to system asymmetry, which gives rise to an avoidance phenomenon in the natural frequency spectrum, and to the investigation of some typical 3-D nonlinear dynamics involving the simultaneous parametric/external excitation due to a harmonically time-varying support movement. Large-amplitude out-of-plane/in-plane multi-modal interactions due to non-planar/planar internal resonances are experimentally observed and complemented by space-time numerical simulation of the associated, geometrically nonlinear, partial-differential equations of parametrically-forced cable motion. Overall, the experimental and numerical results highlight the fundamental linear/nonlinear dynamic characteristics of inclined cables, and the crucial role played by the asymmetry induced by cable inclination, in addition to the significant effects of cable sag and dynamic extensibility

Fibrous hamartoma of Infancy: An Italian multi-istitutional experience.

Fibrous hamartoma of infancy: an Italian multi-institutional experience. Carretto E, Dall'Igna P, Alaggio R, Siracusa F, Granata C, Ferrari A, Cecchetto G. Source Division of Paediatric Surgery, Department of Paediatrics, University of Padua, Padua, Italy. Abstract BACKGROUND: Fibrous hamartoma (FH) of infancy is a benign mesenchymal tumor, occurring as a superficial mass. Complete excision is curative. OBJECTIVE AND METHODS: The clinical features and treatment results of 18 children with FH are described. RESULTS: Local excision was the most common procedure. Surgery was radical in 10 patients, with microscopic residual disease in 6; all of them are alive with no evidence of disease 2 to 49 months after diagnosis. One patient, treated with a local reexcision for macroscopic residual disease (and chemotherapy for a synchronous desmoid fibromatosis) is well 83 months after diagnosis; the last patient, with a lesion of the labia majora, only underwent biopsy and is doing well, awaiting plastic surgery. LIMITATIONS: The results did not reach statistical significance due to difficulties in collecting cases. CONCLUSIONS: FH should be treated by complete excision; in our experience a nonradical excision was also able to achieve the cure. An aggressive approach should be avoided, as the overall prognosis is excellent. PMID: 16635660 [PubMed - indexed for MEDLINE

SURGERY IN MALIGNANT GERM CELL TUMORS OF CHILDHOOD. RESULTS OF THE SECOND ITALIAN COOPERATIVE STUDY TCG 98

Analysis of treatment and results of the patientsenrolled in the Italian TCG-98 Study, still open and comparison of data with those of the previous Studt TCG-9

Experimental and Analytical Investigation into the Effect of Ballasted Track on the Dynamic Response of Railway Bridges under Moving Loads

Ballasted tracks are among the most widespread railway track typologies. The ballast possesses multiple functions. Among them, it significantly affects the dynamic interaction between a rail bridge and a moving load in terms of damping and load distribution. These effects entail accurate modeling of the track-ballast-bridge interaction. The paper presents a finite-difference formulation of the governing equations of the track and the bridge, modeled as Euler-Bernoulli (EB) beams, and coupled by a distributed layer of springs representing the ballast. The two equations are solved under a moving load excitation using a Runge-Kutta family algorithm and the finite-difference method for the temporal and spatial discretization, respectively. The authors validated the mathematical model against the displacement response of a rail bridge with a ballasted substructure. In a first step, the modal parameters of the bridge, obtained from ambient vibration measurements, are used to estimate the bending stiffness of an equivalent EB beam representative of the tested bridge. In a second step, the authors estimated the coupling effect of the ballast by assessing the model sensitivity to the modeling parameters and optimizing the agreement with the experimental data. Comparing the bridge's experimental displacement responses highlights the ballast's significant effect on the load distribution and damping. The considerable difference between the damping estimated from output-only identification and that determined from the displacement response under moving load proves the dominant role of the ballast in adsorbing the vibrations transmitted to the bridge under the train passage and the different damping sources under high-amplitude excitation. The authors discuss the tradeoff between model accuracy and computational effort for a reliable estimation of ballasted tracks response under moving loads

Intensity and location of corrosion on the reliability of a steel bridge

Visual inspections generally represent the initial step of the safety assessment of bridges. In particular, steel railway bridges are particularly prone to corrosion phenomena. Therefore, visual inspections provide the geometric characterization of the conservation state of each structural member, in particular, the size reduction originating from the progress of corrosion. Nonetheless, the geometric definition of corrosion is not directly related to structural safety, depending on the damage location. The paper quantifies and discusses the uncertainties in the safety assessment of trussed bridges associated with the unknown effect of damage location on the stress distribution, given initial knowledge of the number and intensity of damaged members. Is it possible to preliminary assess the structural safety for typological structures without knowing the effect of damage location on the stress re-distribution? This paper discusses these aspects by randomly simulating damage scenarios in a finite element model of a historic steel bridge. The model, validated against the experimental modal parameters and measured deflection under train transit, is used for estimating bidimensional fragility curves as a function of the damage intensity and the number of damaged members. Finally, a safety domain can support the preliminary safety assessment of typological steel railway bridges

Congenital pancreatoblastoma: a case report

The literature describes 15 cases of congenital pancreatoblastoma (PB): 5 had prenatal diagnosis, none had metastases at diagnosis, 7 were associated with BeckwitheWiedemann syndrome (BWS). In 13 cases resection was radical, while in 2 there were macroscopic residues. Only one patient underwent chemotherapy after distant recurrence. All children are alive except one who died because of problems related to BWS. Our goal is to describe the approach adopted in an infant with congenital PB treated in our center. After a prenatal third semester diagnosis of abdominal anechoic lesion, the radiological investigations (ultrasound, MRI) performed at birth described a cystic lesion of unclear nature. We proceeded to laparoscopic exploration, transformed into open approach after the detection of a lesion located in the body of the pancreas; this lesion was resected, preserving the head and tail of pancreas. The histological diagnosis showed a completely excised PB. After excluding metastatic lesions, we decided to perform only careful follow-up without chemotherapy. The follow-up at 12 months is negative. Although PB is a malignant tumor that requires a multidisciplinary treatment, the congenital cases seem to have a less aggressive biological behavior. The treatment, therefore, in case of complete resection, could be only surgical, followed by a careful follow-up. These forms are often associated with congenital BWS, but in our case the patient did not have the typical characteristics of the syndrome

Physics-based models, surrogate models and experimental assessment of the vehicle–bridge interaction in braking conditions

The dynamics of roadway bridges crossed by vehicles moving at variable speed has attracted far less attention than that generated by vehicles travelling at constant velocity. Consequently, the role of some parameters and the combination thereof, as well as influence and accuracy of the modelling strategies, are not fully understood yet. Therefore, a large statistical analysis is performed in the present study to provide novel insights into the dynamic vehicle-bridge interaction (VBI) in braking conditions. To this end, an existing mid-span prestressed concrete bridge is selected as case study. First, several numerical simulations are performed considering alternative vehicle models (i.e., single and two degrees-of-freedom models) and different braking scenarios (i.e., soft and hard braking conditions, with both stationary and nonstationary road roughness models in case of soft braking). The statistical appraisal of the obtained results unfolds some effects of the dynamic VBI modelling in braking conditions that have not been reported in previous studies. Additionally, the use of machine learning techniques is explored for the first time to develop surrogate models able to predict the effect of the dynamic VBI in braking conditions efficiently. These surrogate models are then employed to obtain the fragility curve for the selected prestressed concrete bridge, where the attainment of the decompression moment is considered as relevant limit state. Whilst the derivation of the fragility curve using numerical simulations turned out to be almost unpractical using standard computational resources, the proposed approach that exploits surrogate models carried out via machine learning techniques was demonstrated accurate despite the dramatic reduction of the total elaboration time. Finally, the accuracy of the numerical (physics-based and surrogate) models is evaluated on a statistical basis through comparisons with experimental data

Identification and Model Update of the Dynamic Properties of the San Silvestro Belfry in L'Aquila and Estimation of Bell's Dynamic Actions

The authors investigated the dynamic behaviour of the San Silvestro belfry in L'Aquila (Italy). The 2009 earthquake in L'Aquila caused severe damages to the entire masonry complex. Extensive rehabilitation works, ended in 2019, repaired the structure and enhanced its seismic safety. In this paper, the authors discuss three aspects typical of masonry towers by interpreting the outcomes of Operational Modal Analysis carried out on December 2019: the interactions between the tower and the masonry complex, the dynamic effects of the bell, and the seismic reliability assessment of the tower. Specifically, the experimental mode shapes drive the estimation of an equivalent cross-section, whose principal axes of inertia match with the directions of oscillation of the mode shapes, and the parameters of an equivalent cantilevered beam roughly representative of the tower dynamics. In a second step, a two-degrees-of-freedom analytical model simulates the dynamic coupling between the tower and the more massive bell. The response of the system to a set of seven strong-motion earthquakes yields the assessment of the bell effects over the seismic performance of the masonry tower