Shear strengthening of reinforced concrete beams strengthened using embedded through section steel bars

A new shear strengthening technique, designated as embedded through section (ETS), has been developed to retrofit existing reinforced concrete (RC) elements. This technique calls for holes to be drilled through the beam section; then bars of steel or FRP materials are introduced into these holes and bonded with adhesives to the surrounding concrete. When concrete cover has not the bond and strength requisites to guarantee a strengthening effectiveness for the Externally Bonded and Near Surface Mounted techniques, ETS strategy can be a competitive alternative since it mobilizes the beam’s concrete core which is, generally, free of damage. To explore the potentialities of the ETS technique for the shear strengthening of RC beams, an experimental program was carried out, composed of RC T-cross section beams shear strengthened by using steel bars. The influence on the shear strengthening efficiency of the inclination and shear strengthening ratio of ETS configurations was evaluated; the study also examined the interaction of ETS bars and existing steel stirrups. An increase of shear capacity up to 109% and 136% in the beams with and without internal stirrups, respectively, was obtained. Inclined ETS bars provided higher increase of shear resistance than vertical ones.The authors wish to acknowledge Elletipi S.r.l. (Ferrara, Italy) for supporting the experimental program, Interbau S.r.l. (Milano, Italy) for applying the ETS strengthening system and the ENDIF Geomatic Group (University of Ferrara, Italy) for monitoring the experimental program. The authors also wish to acknowledge the Engineering Department of the University of Ferrara for its financial support

The contribution of embedded through-section bars for the shear resistance of RC

In a recent experimental program, the performance of a novel shear strengthening technique, designated by Embedded Through-Section (ETS), was appraised by performing a series of beam bending tests composed of eight reinforced concrete (RC) beams. According to this strengthening technique, holes are opened through the beam’s section, with the desired inclinations, and bars are introduced into these holes and bonded to the concrete substrate with adhesive materials. The strengthening elements are composed of steel bars bonded to the surrounding concrete with an epoxy adhesive. Based on the obtained results, a significant increase in terms of ultimate load and deflection was registered, and the brittle shear failure more observed in the reference beams was converted in a flexural ductile failure more observed in the strengthened beams. To have a better assessment of the contribution of the ETS bars for the shear resistance of RC beams, material nonlinear analysis were performed with a FEM-based computer program. Finally, the applicability of the ACI 440 and 318 standard specifications for shear resistance were examined. A good agreement between the experimental, numerical and analytical values was obtained

Assessment of the effectiveness of NSM-CFRP flexural strengthening configuration for continuous RC slabs

The experimental programs for the flexural strengthening of reinforced concrete (RC) structures using the Near Surface Mounted (NSM) technique with Fiber Reinforced Polymer (FRP) laminates were, in general, conducted with simply supported beams. Therefore, there is a lack of experimental and theoretical studies on the moment redistribution of statically indeterminate RC elements strengthened with NSM technique. This work explores the influence of the amount of FRP in terms of load carrying capacity, ductility and moment redistribution capacity of continuous RC slab strips. In this way, two span slab strips strengthened in the hogging region were tested. The obtained results were used to assess the predictive performance of a finite element model in the simulation of the nonlinear behavior of the tested slabs. Finally, a parametric study is carried out to investigate the influence of the strengthening arrangement and FRP percentage in terms of load carrying capacity and moment redistribution capacity of continuous RC slab strips flexurally strengthened by the NSM technique.Fundação para a Ciência e a Tecnologia (FCT) - CUTINEMO - Carbon fiber laminates applied according to the near surface mounted technique to increase the flexural resistance to negative moments of continuous reinforced concrete structures” PTDC/ECM/73099/200

Estudo paramétrico do comportamento de faixas de laje contínuas de BA reforçadas à flexão segundo a técnica NSM

Os programas experimentais para o reforço à flexão de estruturas de betão armado (BA) segundo a técnica NSM (Near Surface Mounted, em língua inglesa) com laminados de CFRP (Carbon Fiber Reinforced Polymer, em língua inglesa) são, em geral, realizados com vigas simplesmente apoiadas. Deste modo, há uma carência de estudos experimentais e teóricos sobre a capacidade de redistribuição de momentos em elementos estruturais estaticamente indeterminados e reforçados segundo a técnica NSM. Este trabalho explora a influência da quantidade de CFRP no incremento da capacidade de carga, ductilidade e redistribuição de momentos em faixas de lajes contínuas de BA. Deste modo, faixas de laje de dois tramos foram reforçadas nas regiões de momentos negativos e positivos e posteriormente ensaiadas. Para avaliação do desempenho de modelo numérico, os resultados experimentais são comparados com os valores previstos pela análise efetuada com um programa de cálculo automático baseado no método dos elementos finitos (MEF). Por fim, um estudo paramétrico foi realizado para investigar a influência da configuração de reforço e da percentagem de CFRP no incremento da capacidade de carga e da redistribuição de momentos em faixas de lajes reforçadas segundo à técnica NSM.The experimental programs for the flexural strengthening of reinforced concrete (RC) structures using the Near Surface Mounted (NSM) technique with Carbon Fiber Reinforced Polymer (CFRP) laminates were, in general, conducted with simply supported beams. Therefore, there is a lack of experimental and theoretical studies on the moment redistribution of statically indeterminate RC elements strengthened with NSM technique. This work explores the influence of the amount of CFRP in terms of load carrying capacity, ductility and moment redistribution capacity of continuous RC slab strips. In this way, two span slab strips strengthened in the hogging and sagging regions were tested. Furthermore, for assessing the predictive performance of a FEM-based computer program, the experimental results are compared with values predicted by this software. Finally, a parametric study is carried out to investigate the influence of the strengthening arrangement and CFRP percentage in terms of load carrying capacity and moment redistribution capacity of continuous RC slab strips flexurally strengthened by the NSM technique

Model to simulate the behaviour of RC beams shear strengthened with ETS bars

To predict correctly the deformational and the cracking behavior of reinforced concrete elements failing in shear using a smeared crack approach, the strategy adopted to simulate the crack shear stress transfer is crucial. For this purpose, several strategies for modeling the fracture mode II were implemented in a smeared crack model already existing in the FEM-based computer program, FEMIX. Special development was given to a softening shear stress-shear strain diagram adopted for modeling the crack shear stress transfer. The predictive performance of the implemented constitutive model was assessed by simulating up to failure a series of eight beams tested to appraise the effectiveness of a new strengthening technique to increase the shear resistance of reinforced concrete beams. According to this strengthening technique, designated as Embedded Through-Section (ETS), holes are opened through the beam’s section, with the desired inclinations, and bars are introduced into these holes and bonded to the concrete substrate with adhesive materials. The strengthening elements are composed of steel bars bonded to the surrounding concrete with an epoxy adhesive. By using the properties obtained from the experimental programs for the characterization of the relevant properties of the intervening materials, and deriving from inverse analysis the data for the crack shear softening diagram, the simulations carried out have fitted with high accuracy the deformational and cracking behavior of the tested beams, as well as the strain fields in the reinforcements. The constitutive model is briefly described, and the simulations are presented and analyzed.Fundação para a Ciência e a Tecnologia (FCT

Decoding information for grasping from the macaque dorsomedial visual stream

Neurodecoders have been developed by researchers mostly to control neuroprosthetic devices, but also to shed new light on neural functions. In this study, we show that signals representing grip configurations can be reliably decoded from neural data acquired from area V6A of the monkey medial posterior parietal cortex. Two Macaca fascicularis monkeys were trained to perform an instructed-delay reach-to-grasp task in the dark and in the light toward objects of different shapes. Population neural activity was extracted at various time intervals on vision of the objects, the delay before movement, and grasp execution. This activity was used to train and validate a Bayes classifier used for decoding objects and grip types. Recognition rates were well over chance level for all the epochs analyzed in this study. Furthermore, we detected slightly different decoding accuracies, depending on the task's visual condition. Generalization analysis was performed by training and testing the system during different time intervals. This analysis demonstrated that a change of code occurred during the course of the task. Our classifier was able to discriminate grasp types fairly well in advance with respect to grasping onset. This feature might be important when the timing is critical to send signals to external devices before the movement start. Our results suggest that the neural signals from the dorsomedial visual pathway can be a good substrate to feed neural prostheses for prehensile actions

rTMS over the human medial parietal cortex impairs online reaching corrections

Indirect correlational evidence suggests that the posteromedial sector of the human parietal cortex (area hV6A) is involved in reaching corrections. We interfered with hV6A functions using repetitive transcranial magnetic stimulation (rTMS) while healthy participants performed reaching movements and in-flight adjustments of the hand trajectory in presence of unexpected target shifts. rTMS over hV6A specifically altered action reprogramming, causing deviations of the shifted trajectories, particularly along the vertical dimension (i.e., distance). This study provides evidence of the functional relevance of hV6A in action reprogramming while a sudden event requires a change in performance and shows that hV6A also plays a role in state estimation during reaching. These findings are in line with neurological data showing impairments in actions performed along the distance dimension when lesions occur in the dorsal posterior parietal cortex

Expression of γ-globin genes in β-thalassemia patients treated with sirolimus: results from a pilot clinical trial (Sirthalaclin)

Introduction: β-thalassemia is caused by autosomal mutations in the β-globin gene, which induce the absence or low-level synthesis of β-globin in erythroid cells. It is widely accepted that a high production of fetal hemoglobin (HbF) is beneficial for patients with β-thalassemia. Sirolimus, also known as rapamycin, is a lipophilic macrolide isolated from a strain of Streptomyces hygroscopicus that serves as a strong HbF inducer in vitro and in vivo. In this study, we report biochemical, molecular, and clinical results of a sirolimus-based NCT03877809 clinical trial (a personalized medicine approach for β-thalassemia transfusion-dependent patients: testing sirolimus in a first pilot clinical trial, Sirthalaclin). Methods: Accumulation of γ-globin mRNA was analyzed using reverse-transcription quantitative polymerase chain reaction (PCR), while the hemoglobin pattern was analyzed using high-performance liquid chromatography (HPLC). The immunophenotype was analyzed using a fluorescence-activated cell sorter (FACS), with antibodies against CD3, CD4, CD8, CD14, CD19, CD25 (for analysis of peripheral blood mononuclear cells), or CD71 and CD235a (for analysis of in vitro cultured erythroid precursors). Results: The results were obtained in eight patients with the β+/β+ and β+/β0 genotypes, who were treated with a starting dosage of 1 mg/day sirolimus for 24–48 weeks. The first finding of this study was that the expression of γ-globin mRNA increased in the blood and erythroid precursor cells isolated from β-thalassemia patients treated with low-dose sirolimus. This trial also led to the important finding that sirolimus influences erythropoiesis and reduces biochemical markers associated with ineffective erythropoiesis (excess free α-globin chains, bilirubin, soluble transferrin receptor, and ferritin). A decrease in the transfusion demand index was observed in most (7/8) of the patients. The drug was well tolerated, with minor effects on the immunophenotype, and an only side effect of frequently occurring stomatitis. Conclusion: The data obtained indicate that low doses of sirolimus modify hematopoiesis and induce increased expression of γ-globin genes in a subset of patients with β-thalassemia. Further clinical trials are warranted, possibly including testing of the drug in patients with less severe forms of the disease and exploring combination therapies. © The Author(s), 2022

The Gradient Anchorage Method for Prestressed CFRP Strips: from the Development to the Strengthening of an 18 M Long Bridge Girder

The external bonding of carbon fiber-reinforced polymer (CFRP) strips by two-component epoxy adhesive on the concrete surfaces of buildings and bridges is a retrofitting method accepted worldwide. The gradient anchorage (GA) is an anchoring method especially developed to anchor prestressed CFRP strips to concrete elements without a need for mechanical clamping after the installation phase. This method takes advantage of the adhesives property to undergo accelerated curing when heated. The results of more than fifteen years of research on the development of the gradient anchorage at the Swiss Federal Laboratories for Materials Science and Technology (Empa) are presented in this paper. The basic principles and application steps are explained, and the main results starting from the development of the technique up to the testing of real scale girders are described, and the new challenges posed by this innovative system are highlighted. The gradient anchorage is a valid alternative to a mechanically anchored system for prestressed FRP (P-FRP)