Numerical analysis of reinforced concrete circular columns strengthening with CFRP under concentric and eccentric loadings

The purpose of this study is to explore the numerical behavior of circular Reinforced Concrete (RC) short columns with different degrees of confinement with Carbon Fiber Reinforced Polymer (CFRP) (0%, 25%, 50%, and 100%) wraps under concentric and eccentric loading. The numerical analysis carried out by using an improved Concrete Damage plasticity (CDP) model implemented in ABAQUS software for finite element (FE) analysis. The FE model simulated a total of twenty-four numerical specimens. The findings were matched to published experimental test results in the literature. The findings of the FE model and the experimental data were good similar. As a consequence, the model was found to be valid. The numerical results shows that as load eccentricity increased, the load carrying capacity of columns decreased for unconfined specimens, whereas the decline in strength for confined specimens becomes limited as the degrees of confinement ratio increased. In addition, increasing the CFRP confinement ratio improves the column's load-bearing capability at the same load eccentricity

Nouvelle approche de modélisation de milieux poreux. Application à l'os trabéculaire

Dans de nombreux domaines tels que la science des matériaux ou l'imagerie médicale, il est intéressant d'évaluer les propriétés mécaniques d'une structure. Pour ce faire, l'analyse par éléments finis est souvent utilisée. Cependant, son application à des milieux poreux complexes est limitée, car le nombre d'éléments nécessaires pour représenter la structure interne est très grand. Dans cette communication, nous proposons une nouvelle approche par éléments finis qui prend en compte la topologie de la structure étudiée. Pour cela, nous implémentons et améliorons une technique récente basée sur le squelette 3D, permettant de caractériser des milieux poreux complexes. Chaque travée de la structure interne peut alors être représentée par une chaîne de poutres rectilignes auxquelles sont attribuées les propriétés de l'arche. Cette approche permet de réduire considérablement le temps de calcul nécessaire à la simulation mécanique par éléments finis tout en présentant une bonne adéquation avec une technique de référence. Nous avons évalué cette technique sur des vecteurs de test, puis appliqué notre méthode sur des échantillons d'os trabéculaire afin d'en quantifier précisément l'élasticité. Ce nouveau procédé de modélisation donne de meilleurs résultats de rigidité par rapport aux techniques à éléments poutre existantes sur des vecteurs de test. Cette tendance se confirme également lors de son application à l'étude de la microarchitecture de l'os trabéculaire

A new anisotropy index on trabecular bone radiographic images using the fast Fourier transform

BACKGROUND: The degree of anisotropy (DA) on radiographs is related to bone structure, we present a new index to assess DA. METHODS: In a region of interest from calcaneus radiographs, we applied a Fast Fourier Transform (FFT). All the FFT spectra involve the horizontal and vertical components corresponding respectively to longitudinal and transversal trabeculae. By visual inspection, we measured the spreading angles: Dispersion Longitudinal Index (DLI) and Dispersion Transverse Index (DTI) and calculated DA = 180/(DLI+DTI). To test the reliability of DA assessment, we synthesized images simulating radiological projections of periodic structures with elements more or less disoriented. RESULTS: Firstly, we tested synthetic images which comprised a large variety of structures from highly anisotropic structure to the almost isotropic, DA was ranging from 1.3 to 3.8 respectively. The analysis of the FFT spectra was performed by two observers, the Coefficients of Variation were 1.5% and 3.1 % for intra-and inter-observer reproducibility, respectively. In 22 post-menopausal women with osteoporotic fracture cases and 44 age-matched controls, DA values were respectively 1.87 ± 0.15 versus 1.72 ± 0.18 (p = 0.001). From the ROC analysis, the Area Under Curve (AUC) were respectively 0.65, 0.62, 0.64, 0.77 for lumbar spine, femoral neck, total femoral BMD and DA. CONCLUSION: The highest DA values in fracture cases suggest that the structure is more anisotropic in osteoporosis due to preferential deletion of trabeculae in some directions

Global Retinoblastoma Presentation and Analysis by National Income Level.

Importance: Early diagnosis of retinoblastoma, the most common intraocular cancer, can save both a child's life and vision. However, anecdotal evidence suggests that many children across the world are diagnosed late. To our knowledge, the clinical presentation of retinoblastoma has never been assessed on a global scale. Objectives: To report the retinoblastoma stage at diagnosis in patients across the world during a single year, to investigate associations between clinical variables and national income level, and to investigate risk factors for advanced disease at diagnosis. Design, Setting, and Participants: A total of 278 retinoblastoma treatment centers were recruited from June 2017 through December 2018 to participate in a cross-sectional analysis of treatment-naive patients with retinoblastoma who were diagnosed in 2017. Main Outcomes and Measures: Age at presentation, proportion of familial history of retinoblastoma, and tumor stage and metastasis. Results: The cohort included 4351 new patients from 153 countries; the median age at diagnosis was 30.5 (interquartile range, 18.3-45.9) months, and 1976 patients (45.4%) were female. Most patients (n = 3685 [84.7%]) were from low- and middle-income countries (LMICs). Globally, the most common indication for referral was leukocoria (n = 2638 [62.8%]), followed by strabismus (n = 429 [10.2%]) and proptosis (n = 309 [7.4%]). Patients from high-income countries (HICs) were diagnosed at a median age of 14.1 months, with 656 of 666 (98.5%) patients having intraocular retinoblastoma and 2 (0.3%) having metastasis. Patients from low-income countries were diagnosed at a median age of 30.5 months, with 256 of 521 (49.1%) having extraocular retinoblastoma and 94 of 498 (18.9%) having metastasis. Lower national income level was associated with older presentation age, higher proportion of locally advanced disease and distant metastasis, and smaller proportion of familial history of retinoblastoma. Advanced disease at diagnosis was more common in LMICs even after adjusting for age (odds ratio for low-income countries vs upper-middle-income countries and HICs, 17.92 [95% CI, 12.94-24.80], and for lower-middle-income countries vs upper-middle-income countries and HICs, 5.74 [95% CI, 4.30-7.68]). Conclusions and Relevance: This study is estimated to have included more than half of all new retinoblastoma cases worldwide in 2017. Children from LMICs, where the main global retinoblastoma burden lies, presented at an older age with more advanced disease and demonstrated a smaller proportion of familial history of retinoblastoma, likely because many do not reach a childbearing age. Given that retinoblastoma is curable, these data are concerning and mandate intervention at national and international levels. Further studies are needed to investigate factors, other than age at presentation, that may be associated with advanced disease in LMICs

Travel burden and clinical presentation of retinoblastoma: analysis of 1024 patients from 43 African countries and 518 patients from 40 European countries

BACKGROUND: The travel distance from home to a treatment centre, which may impact the stage at diagnosis, has not been investigated for retinoblastoma, the most common childhood eye cancer. We aimed to investigate the travel burden and its impact on clinical presentation in a large sample of patients with retinoblastoma from Africa and Europe. METHODS: A cross-sectional analysis including 518 treatment-naïve patients with retinoblastoma residing in 40 European countries and 1024 treatment-naïve patients with retinoblastoma residing in 43 African countries. RESULTS: Capture rate was 42.2% of expected patients from Africa and 108.8% from Europe. African patients were older (95% CI -12.4 to -5.4, p<0.001), had fewer cases of familial retinoblastoma (95% CI 2.0 to 5.3, p<0.001) and presented with more advanced disease (95% CI 6.0 to 9.8, p<0.001); 43.4% and 15.4% of Africans had extraocular retinoblastoma and distant metastasis at the time of diagnosis, respectively, compared to 2.9% and 1.0% of the Europeans. To reach a retinoblastoma centre, European patients travelled 421.8 km compared to Africans who travelled 185.7 km (p<0.001). On regression analysis, lower-national income level, African residence and older age (p<0.001), but not travel distance (p=0.19), were risk factors for advanced disease. CONCLUSIONS: Fewer than half the expected number of patients with retinoblastoma presented to African referral centres in 2017, suggesting poor awareness or other barriers to access. Despite the relatively shorter distance travelled by African patients, they presented with later-stage disease. Health education about retinoblastoma is needed for carers and health workers in Africa in order to increase capture rate and promote early referral

The global retinoblastoma outcome study : a prospective, cluster-based analysis of 4064 patients from 149 countries

DATA SHARING : The study data will become available online once all analyses are complete.BACKGROUND : Retinoblastoma is the most common intraocular cancer worldwide. There is some evidence to suggest that major differences exist in treatment outcomes for children with retinoblastoma from different regions, but these differences have not been assessed on a global scale. We aimed to report 3-year outcomes for children with retinoblastoma globally and to investigate factors associated with survival. METHODS : We did a prospective cluster-based analysis of treatment-naive patients with retinoblastoma who were diagnosed between Jan 1, 2017, and Dec 31, 2017, then treated and followed up for 3 years. Patients were recruited from 260 specialised treatment centres worldwide. Data were obtained from participating centres on primary and additional treatments, duration of follow-up, metastasis, eye globe salvage, and survival outcome. We analysed time to death and time to enucleation with Cox regression models. FINDINGS : The cohort included 4064 children from 149 countries. The median age at diagnosis was 23·2 months (IQR 11·0–36·5). Extraocular tumour spread (cT4 of the cTNMH classification) at diagnosis was reported in five (0·8%) of 636 children from high-income countries, 55 (5·4%) of 1027 children from upper-middle-income countries, 342 (19·7%) of 1738 children from lower-middle-income countries, and 196 (42·9%) of 457 children from low-income countries. Enucleation surgery was available for all children and intravenous chemotherapy was available for 4014 (98·8%) of 4064 children. The 3-year survival rate was 99·5% (95% CI 98·8–100·0) for children from high-income countries, 91·2% (89·5–93·0) for children from upper-middle-income countries, 80·3% (78·3–82·3) for children from lower-middle-income countries, and 57·3% (52·1-63·0) for children from low-income countries. On analysis, independent factors for worse survival were residence in low-income countries compared to high-income countries (hazard ratio 16·67; 95% CI 4·76–50·00), cT4 advanced tumour compared to cT1 (8·98; 4·44–18·18), and older age at diagnosis in children up to 3 years (1·38 per year; 1·23–1·56). For children aged 3–7 years, the mortality risk decreased slightly (p=0·0104 for the change in slope). INTERPRETATION : This study, estimated to include approximately half of all new retinoblastoma cases worldwide in 2017, shows profound inequity in survival of children depending on the national income level of their country of residence. In high-income countries, death from retinoblastoma is rare, whereas in low-income countries estimated 3-year survival is just over 50%. Although essential treatments are available in nearly all countries, early diagnosis and treatment in low-income countries are key to improving survival outcomes.The Queen Elizabeth Diamond Jubilee Trust and the Wellcome Trust.https://www.thelancet.com/journals/langlo/homeam2023Paediatrics and Child Healt

A Review-Behavior of Reinforced Concrete Exterior Beam-Column Connections under Cyclic Loading

In many seismically active regions worldwide, massive reinforced concrete (RC) structures built before the 1970s existed. These older RC buildings, in countries having seismic history, were designed for gravity loads only. Anyway, the beam-column connections influence the structures where the functions of connection shortage by transport the forces like shear, moment, and torsion through the beam to the column. Also, it could behave in a ductile manner to help the structure resist the seismic, as simulate the seismic loading by high and low cyclic loading. Due to the failure of external joints more than the internal beam-column joints, this review focuses on the behavior of exterior beam-column joints under cyclic loading, consequently simulated the behavior under an earthquake and the reinforcement detailed

Streamers in seismic engineering

W artykule przedstawiono przegląd strimerów sejsmicznych wykorzystywanych w badaniach sejsmiki inżynierskiej. Znajdują one zastosowanie przede wszystkim w badaniach podłoża gruntowego szlaków komunikacyjnych. Pomiary takimi urządzeniami można również wykonywać w innych celach badawczych, lecz w warunkach terenowych o płaskim lub słabo zmiennym ukształtowaniu. Obecnie strimery sejsmiczne używane są w warunkach, gdzie długość i liczba profili pomiarowych zmuszają do wielokrotnego rozstawiania i składania sprzętu sejsmicznego. Autorzy definiują pojęcie strimera sejsmicznego. Opracowano klasyfikacje ze względu na rodzaje konstrukcji i sposoby mocowania czujników w strimerach. Scharakteryzowano i zilustrowano zasadę działania oraz opisano obecne stadium i kierunek rozwoju technologii strimerów. Przedstawione zostały możliwe konfiguracje strimerów sejsmicznych wraz z pojazdami ciągnącymi i źródłami sejsmicznymi wykorzystywanymi w pomiarach. Zaprezentowano przykłady strimerów sejsmicznych stosowanych w sejsmice inżynierskiej, ze szczegółowymi ich opisami. Dokonano porównania konstrukcji wybranych strimerów sejsmicznych.This paper presents a detailed overview of land streamers used in seismic engineering. They are commonly implemented in ground reconnaissance along communication routes. Other surveys can be also carried out with this systems, nevertheless field condition should be flat or moderately unchangeable. Nowadays land streamers are used when length and number of seismic profiles force us to make several changes in classical system set-up. Authors defined the term of land streamer. Classification is made due to construction and sensor handle. Characterization and illustration of land streamer principle of operation has been presented. Current direction of technical development was described. The authors presented possible configurations with different towing vehicles and seismic sources. Exemplary land streamers used in industry has been presented with a detailed description. Constructions of selected land streamers have been compered

An overview of technical parameters of geophones used in seismic engineering

W sejsmice inżynierskiej czujniki służą jako rejestratory drgań mechanicznych ośrodka geologicznego. W pracy przedstawiono ich klasyfikację. Do najbardziej powszechnych należą geofony, które stosuje się do badań geologiczno-inżynierskich, hydrogeologicznych, geotechnicznych, geomechanicznych oraz w górnictwie. Prawidłowy dobór ich parametrów technicznych ma znaczący wpływ na jakość uzyskanych danych oraz rozdzielczość metody. Najważniejszymi parametrami, które należy wziąć po uwagę to: częstotliwość własna, czułość, tłumienie, zniekształcenia harmoniczne i oporność cewki. Bardzo istotny jest również sposób przytwierdzenia geofonu do podłoża, ponieważ może on znacząco wpływać na odpowiedź impulsową układu pomiarowego. Światowi producenci geofonów oferują szeroki zakres urządzeń o różnych wartościach parametrów technicznych do jak najlepszej akwizycji danych w konkretnych zastosowaniach sejsmicznych. Dodatkowo, nowoczesne geofony trójskładowe mogą rejestrować jednocześnie w trzech kierunkach, co ułatwia identyfikację fal sejsmicznych i opis pola falowego. W artykule dokonano możliwie szerokiego przeglądu podstawowych parametrów technicznych geofonów czołowych producentów na świecie. Sformułowano kryteria doboru geofonów do badań sejsmicznych.Sensors are used in seismic engineering to record mechanical oscillations of geological medium. This paper presents a classification of the applied detectors. The most common are geophones which used in geological engineering, hydrogeology, geotechnical engineering and mining. Proper choice of the geophone technical parameters is essential for the obtained data quality and seismic resolution. The most important parameters are natural frequency, sensitivity, damping, harmonic distortion and coil resistivity. Geophone coupling to the ground is crucial because of its great impact on impulse response. The global producers of geophones offer a wide range of devices with different technical parameters in order to obtain the best seismic acquisition. Moreover, the newest three-component geophones record in three dimensions simultaneously. It simplifies wave identification and characterization of the wave field. This paper presents a possibly wide overview of geophone basic technical parameters produced by the leading geophysical companies worldwide. Criteria of their selection were formulated as well