Comportamiento diferido en estado fisurado de elementos de UHPFRC a flexotracción

[ES] En este trabajo se analiza el comportamiento a largo plazo de elementos de Hormigón de Ultra Alta Resistencia Reforzados con Fibras (en inglés UHPFRC) mediante una campaña experimental con tres tipos de probetas: cilíndricas (Ø100x200mm), prismáticas “R” (150x150x600mm) y prismáticas “S” (150x40x600mm). Se realizaron ensayos de retracción y de fluencia a flexión en estado fisurado, así como de caracterización tanto a resistencia a compresión como flexotracción. Las probetas cilíndricas se destinaron a retracción, fluencia en compresión y resistencia a compresión simple, en tanto que las prismáticas se destinaron a fluencia en flexión y resistencia a flexotracción. En las probetas R se realizó una entalla de 50 mm de profundidad y fueron prefisuradas hasta alcanzar un Crack Mouth Opening Displacement (CMOD) de 0,65mm. Las probetas S fueron prefisuradas sin entalla hasta alcanzar una pérdida de rigidez del 50%. Se montaron las probetas en los bastidores de fluencia en donde se mantuvo un nivel de carga del 50% de la resistencia residual obtenida del ensayo de prefisura para las probetas R y un nivel de carga entre el 68% y el 86% para las probetas S. Los ensayos de fluencia en flexión abarcaron 270 días, apreciándose una estabilizando más temprana para las probetas tipo S. De los resultados del ensayo de fluencia se calcularon los coeficientes y se compararon con los propuestos por distintos autores para el UHPFRC, dando como resultado que los valores de fluencia obtenidos de manera experimental son ligeramente menores que los propuestos quedando estos del lado de la seguridad.Los autores agradecen la financiación recibida desde el Ministerio de Economía y Competitividad a través de los Proyectos "BIA2012-35776 (FISNE)” y “BIA2016-78460- C3-1-R (BESHO/DEHMAR)”.Llano-Torre, A.; López, J.; Martí-Vargas, JR.; Serna, P. (2018). Comportamiento diferido en estado fisurado de elementos de UHPFRC a flexotracción. En HAC 2018. V Congreso Iberoamericano de hormigón autocompactable y hormigones especiales. Editorial Universitat Politècnica de València. 361-372. https://doi.org/10.4995/HAC2018.2018.6144OCS36137

Pull-out and push-in tests of bonded steel strands

Martí Vargas, JR. (2013). Pull-out and push-in tests of bonded steel strands. Magazine of Concrete Research. 65(18):1128-1131. doi:10.1680/macr.13.00061S112811316518Balázs LG .Bond Model with Non-Linear Bond-Slip Law, 1987, Politecnico di Milano, Italy, 395–430, Studi e Ricerche, Post-Graduate Course for Reinforced Concrete Structures, V.8/86.Balazs, G. L. (1992). Transfer Control of Prestressing Strands. PCI Journal, 37(6), 60-71. doi:10.15554/pcij.11011992.60.71Balazs, G. L. (1993). Transfer Length of Prestressing Strand as a Function of Draw-In and Initial Prestress. PCI Journal, 38(2), 86-93. doi:10.15554/pcij.03011993.86.93Balázs, G. L. (2007). Connecting Reinforcement to Concrete by Bond. Beton- und Stahlbetonbau, 102(S1), 46-50. doi:10.1002/best.200710109Carmo RNF .Ancoragem de Armaduras Pré-Esforçadas por Pré-Tensão. MSc thesis, 1999, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, Portugal, (in Portuguese).Faria, D. M. V., Lúcio, V. J. G., & Pinho Ramos, A. (2011). Pull-out and push-in tests of bonded steel strands. Magazine of Concrete Research, 63(9), 689-705. doi:10.1680/macr.2011.63.9.689Faria, D. M. V., Lúcio, V. J. G., & Ramos, A. P. (2011). Strengthening of flat slabs with post-tensioning using anchorages by bonding. Engineering Structures, 33(6), 2025-2043. doi:10.1016/j.engstruct.2011.02.039Faria, D. M. V., Lúcio, V. J. G., & Pinho Ramos, A. (2012). Post-punching behaviour of flat slabs strengthened with a new technique using post-tensioning. Engineering Structures, 40, 383-397. doi:10.1016/j.engstruct.2012.03.014Laldji S .Bond Characteristics of Prestressing Strand in Grout. MPhil thesis, 1987, University of Leicester, UK.Laldji, S., & Young, A. G. (1988). Bond between steel strand and cement grout in ground anchorages. Magazine of Concrete Research, 40(143), 90-98. doi:10.1680/macr.1988.40.143.90Lopes, S. M. R., & do Carmo, R. N. F. (2002). Bond of prestressed strands to concrete: transfer rate and relationship between transmission length and tendon draw-in. Structural Concrete, 3(3), 117-126. doi:10.1680/stco.2002.3.3.117Martí-Vargas, J. R., Serna-Ros, P., Fernández-Prada, M. A., Miguel-Sosa, P. F., & Arbeláez, C. A. (2006). Test method for determination of the transmission and anchorage lengths in prestressed reinforcement. Magazine of Concrete Research, 58(1), 21-29. doi:10.1680/macr.2006.58.1.21Marti-Vargas, J. R., Arbelaez, C. A., Serna-Ros, P., Navarro-Gregori, J., & Pallares-Rubio, L. (2007). Analytical model for transfer length prediction of 13 mm prestressing strand. Structural Engineering and Mechanics, 26(2), 211-229. doi:10.12989/sem.2007.26.2.211Palmer, K. D., & Schultz, A. E. (2011). Experimental investigation of the web-shear strength of deep hollow-core units. PCI Journal, 56(4), 83-104. doi:10.15554/pcij.09012011.83.10

Producción de ovino de carne en medio semiárido

Unpublishe

Creep and residual properties of cracked macro-synthetic fibre reinforced concretes

[EN] This study analysed the creep behaviour of five concretes incorporating 0.5% by volume of four macro-synthetic fibres (MSFs) and one steel fibre. After 28 d moist curing, prisms were pre-loaded up to a crack opening of 0.5 mm and held for 90 d in three different environments - ambient laboratory air, seawater at 45 degrees C and air flow at 45 degrees C. Sustained loads were then applied on three specimens from each group while the other prisms remained unloaded. The remaining residual capacity was evaluated by bending tests. It was concluded that the residual capacity of cracked MSF concretes is not affected by long-term loading.The authors wish to thank the technicians of ICITECH, where the experimental work was developed. The financial support of the project FISNE with reference BIA2012-35776, supported by the Spanish Ministry of Economy and Competiveness and the FEDER fund, is also gratefully acknowledged. The doctoral scholarship of M. E. Bossio was supported by the project EuroTANGO (European Commission - EACEA).Serna Ros, P.; Martí Vargas, JR.; Bossio, ME.; Zerbino, R. (2016). Creep and residual properties of cracked macro-synthetic fibre reinforced concretes. Magazine of Concrete Research. 68(4):197-207. https://doi.org/10.1680/macr.15.00111S19720768

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Evolution of Trypanosoma cruzi infection in resistant and susceptible mice. Evolución de la infección con Trypanosoma cruzi en cepas susceptibles y resistentes de ratones

Mice from ACA and A.Sn strains were equally susceptible (100% mortality) to intraperitoneal infection with 2000 blood trypomastigotes from Tulahuen strain of Trypanosoma cruzi, while A.Sw and HTI strains were resistant (100% survival). However mice from A.Sw and HTI strains showed significantly higher level of parasitemia than the susceptible strains. The histopathology of miocardial and skeletal muscle was evaluated in the susceptible and resistant strains of mice. In the first ten days post-infection no significant differences in tissue damage were observed. However in the third week of infection, while A.Sw and HTI mice showed recovery of tissue lessions, the susceptible A.Sn and ACA showed increased tissue damage although no blood forms and intracellular parasites were detected. Serum samples from infected mice were tested by dot-immunoradiometric assay, for reactivity against recombinant antigens 1,2,13,26,30,36 and SAPA of T. cruzi. All mice sera only reacted with clones 13 and SAPA, suggesting that this reactivity seems not to be involved in susceptibility or resistance to infection with Tulahuen strain of T. cruz

Temperature Gradients in Bridge Concrete I-Girders under Heat Wave

[EN] This paper presents an experimental research work to determine temperature gradients in concrete bridge girders under natural environmental conditions. Three AASHTO Type I-girders having different configurations (with and without wide top flanges) were considered in the experimental program. Temperature was monitored in the bridge girders to determine the vertical and transverse temperature gradients in a predeck placement condition. It was found that uneven heating of optimized bridge girder sections results in large nonlinear temperature gradients. The current AASHTO design standard, which only uses a nonlinear vertical but no transversal temperature gradient, was found inaccurate to predict both shape and magnitude of temperature gradients for the analyzed girders.This research is supported by the University of Arkansas at Fayetteville, Ton Duc Thang University, and Southern Plains Transportation Center. The authors are thankful to a number of graduate students for their help during the experimental program.Hagedorn, R.; Martí Vargas, JR.; Dang, C.; Hale, W.; Floyd, R. (2019). Temperature Gradients in Bridge Concrete I-Girders under Heat Wave. Journal of Bridge Engineering. 24(8):1-14. https://doi.org/10.1061/(ASCE)BE.1943-5592.0001454S11424

Non-motor symptoms burden, mood, and gait problems are the most significant factors contributing to a poor quality of life in non-demented Parkinson's disease patients: Results from the COPPADIS Study Cohort

[Objective] To identify factors related to a poor health-related and global quality of life (QoL) in a cohort of non-demented Parkinson's disease (PD) patients and compare to a control group.[Methods] The data correspond to the baseline evaluation of the COPPADIS-2015 Study, an observational, 5-year follow-up, multicenter, evaluation study. Three instruments were used to assess QoL: (1) the 39-item Parkinson's disease Questionnaire (PDQ-39), (2) a subjective rating of global QoL (PQ-10), and (3) the EUROHIS-QOL 8-item index (EUROHIS-QOL8). Multiple linear regression methods were used to evaluate the direct impact of different variables on these QoL measures.[Results] QoL was worse in PD patients (n = 692; 62.6 ± 8.9 years old, 60.3% males) than controls (n = 206; 61 ± 8.3 years old, 49.5% males): PDQ-39, 17.1 ± 13.5 vs 4.4 ± 6.3 (p < 0.0001); PQ-10, 7.3 ± 1.6 vs 8.1 ± 1.2 (p < 0.0001); EUROHIS-QOL8, 3.8 ± 0.6 vs 4.2 ± 0.5 (p < 0.0001). A high correlation was observed between PDQ-39 and Non-Motor Symptoms Scale (NMSS) (r = 0.72; p < 0.0001), and PDQ-39 and Beck Depression Inventory-II (BDI-II) (r = 0.65; p < 0.0001). For health-related QoL (PDQ-39), non-motor symptoms burden (NMSS), mood (BDI-II), and gait problems (Freezing Of Gait Questionnaire [FOGQ]) provided the highest contribution to the model (β = 0.32, 0.28, and 0.27, respectively; p < 0.0001); whereas mood and gait problems contributed the most to global QoL (PQ-10, β = -0.46 and −0.21, respectively; EUROHIS-QOL8, β = -0.44 and −0.23, respectively).[Conclusions] QoL is worse in PD patients than in controls. Mood, non-motor symptoms burden, and gait problems seem to be the most relevant factors affecting health-related and global perceived QoL in non-demented PD patients.Peer reviewe