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The near-surface mounted (NSM) technique with fiber reinforced polymer (FRP) reinforcement as strengthening system for concrete structures has been broadly studied during the last years. The efficiency of the NSM FRP-to-concrete joint highly depends on the bond between both materials, which is characterized by a local bond-slip law. This paper studies the effect of the shape of the local bond-slip law and its parameters on the global response of the NSM FRP joint in terms of load capacity, effective bond length, slip, shear stress, and strain distribution along the bonded length, which are essential parameters on the strengthening design. A numerical procedure based on the finite difference method to solve the governing equations of the FRP-to-concrete joint is developed. Pull-out single shear specimens are tested in order to experimentally validate the numerical results. Finally, a parametric study is performed. The effect of the bond-shear strength slip at the bond strength, maximum slip, and friction branch on the parameters previously described is presented and discussed ; This research was funded by the Spanish Government (MINECO), Project Ref. BIA2017-84975-C2-2-P

The use of mechanical anchorage systems can delay or prevent premature failure of RC structures with externally bonded fiber-reinforced polymer (EB-FRP) laminates. This work reports the results of an experimental program aimed at studying the bond behavior of a metallic anchorage plate, typically used for prestressed EB-FRP systems. The overall experimental program comprised 17 concrete prisms with carbon fiber–reinforced polymer (CFRP) laminates externally bonded to the concrete with mechanical anchorage at the end and to which different levels of normal stress were applied. Direct shear tests were carried out using two configurations: (1) steady-state tests, in which the laminate was pulled out from the block with increasing force and at constant temperature (20°C, 60°C, and 80°C); and (2) transient tests, in which the laminate was pulled out with constant force (0.36%, 0.45% and 0.54% of strain) and the temperature was gradually increased. Experimental results showed that the ultimate capacity of the mechanical anchorage can decrease by 44%–59% depending on the temperature and level of normal stress ; This work was supported by FEDER funds through the Operational Program for Competitiveness Factors—COMPETE and National Funds through the Portuguese Foundation for Science and Technology (FCT) under Project No. FRPLongDur POCI-01-0145-FEDER-016900 (FCT PTDC/ECM-EST/1282/2014) and partly financed by Project POCI-01-0145-FEDER-007633. The first author acknowledges Grant No. SFRH/BD/98309/2013 provided by FCT. The second author acknowledges the Spanish Government (Ministerio de Educación, Cultura y Deporte) for the José Castillejo grant ref. CAS16/00288

Structural adhesives are commonly used to bond Fibre Reinforced Polymer (FRP) materials to Reinforced Concrete (RC) structures so they can withstand service conditions. This paper presents an experimental study on the combined effect of sustained loading and service steady and cyclic temperatures on the thermophysical and mechanical properties of an epoxy adhesive. Four experimental series consisting of nine adhesive tensile dog-bone specimens were tested under sustained loading and temperatures ranging between 18 °C and 43 °C for a duration of 1000 h. Moreover, the residual properties of the adhesive have been evaluated through instantaneous tensile tests and Differential Scanning Calorimetry (DSC) after sustained loading tests. Results showed a significant increase in strain with time, a reduction in the mechanical properties, and an increase in the glass transition temperature and curing degree of the adhesive after the exposure at service conditions and sustained loading. From this work it could be concluded that the combination of sustained loading and service temperatures have a significant effect on the creep behaviour of the adhesive, and cyclic temperatures have a greater effect on the adhesive even though the average temperature is below the steady temperature. ; This work was supported by the Spanish Government (MINECO) [Project Ref. BIA2017-84975-C2-2-P]; the University of Girona [grant IFUdG2018/28 and MOB2019]; and the Generalitat de Catalunya [grant number 2019FI_B 00054]

This paper presents a study of the effect of high service temperature (near or beyond glass transition temperature (Tg) of structural epoxy adhesive) on the behavior of near-surface mounted (NSM) carbon fiber-reinforced polymer (CFRP)-strengthened reinforced concrete (RC) beams. The study includes experimental work as well as analytical and numerical analysis. To this end, fourteen beams have been tested up to failure in two different series. In series 1, specimens with three different CFRP areas have been tested at two different temperatures (i.e., 20 and 40 °C). In series 2, and with the aim of evaluating the effect of higher temperatures, only one CFRP area was tested under four different temperatures (i.e., 20, 60, 70, and 85 °C). Experimental results are evaluated in terms of load-deflections, failure modes, and bond performance. Furthermore, the experimental load-deflection curves are satisfactorily compared to both analytical predictions and finite element (FE) numerical simulations. In both cases, shrinkage and temperature effects on the short-term response of flexural elements have been accounted for. No significant reduction in stiffness and ultimate load was observed for specimens being tested up to 60 °C (in the range of epoxy Tg), showing FRP rupture failure in all of them. For specimens under 70 and 85 °C, the failure mode changed from FRP rupture to FRP end debonding and concrete crushing, respectively ; This research was funded by the Spanish Government (MINECO) [Project Ref. BIA2017-84975-C2-2-P]; the Generalitat de Catalunya [grant number 2019FI_B 00054] and the University of Girona [grant number IFUdG2018/28]

This paper presents a study into bond behaviour under sustained loading of Near-Surface Mounted (NSM) Carbon-Fibre Reinforced Polymers (CFRP) concrete joints, through an experimental programme and a numerical analysis. The experimental programme consisted of eight NSM CFRP-concrete pull-out specimens tested under sustained loading and laboratory conditions (20 °C and 55%HR) inside a climatic chamber. Previously, the instantaneous bond behaviour of the NSM CFRP-concrete joint was studied using 18 specimens tested until failure. Furthermore, the tensile behaviour of the adhesive under instantaneous and sustained loading was studied at different loading levels under the same environmental conditions. Finally, a numerical procedure was proposed to predict the bonded joint response under sustained loading. A creep coefficient and a strength reduction factor were applied to the instantaneous bond-slip law to simulate the degrading effect the sustained loading had on the behaviour of the bonded joint. Good agreement between the experimental and numerical results was obtained for the tested parameters, however, further research needs to be carried out in order to extrapolate this methodology to other cases ; This work was supported by the Spanish Government (MINECO) [Project Ref. BIA2017-84975-C2-2-P]; the University of Girona [grant number IFUdG2018/28]; and the Generalitat de Catalunya [grant number 2019FI_B 00054]

El pdf del artículo es la versión de autor. ; Vitamin D receptor (VDR) mediates the antitumoral action of the active vitamin D metabolite 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3). VDR expression is lost during colon cancer progression causing unresponsiveness to 1,25(OH)2D3 and its analogs. Previously, Snail1, an inducer of epithelial-to-mesenchymal transition (EMT), was reported to inhibit VDR expression. Here, we show that Snail2/Slug, but not other EMT inducers such as Zeb1, Zeb2, E47 or Twist1, represses VDR gene promoter. Moreover, Snail2 and Snail1 show additive repressing effect on VDR promoter. Snail2 inhibits VDR RNA and protein and blocks the induction of E-cadherin and an adhesive phenotype by 1,25(OH)2D3. Snail2 reduces the ligand-induced VDR transcriptional activation of a consensus response element and of the CYP24 promoter. Concordantly, Snail2 inhibits the induction of CYP24 RNA and p21CIP1, filamin A and vinculin proteins and the repression of c-MYC by 1,25(OH)2D3. Additionally, Snail2 abrogates β-catenin nuclear export and the antagonism of the transcriptional activity of β-catenin–T-cell factor complexes by 1,25(OH)2D3. SNAI2 expression is upregulated in 58% of colorectal tumors and correlates inversely with that of VDR. However, VDR downregulation is higher in tumors coexpressing SNAI2 and SNAI1 than in those expressing only one of these genes. Together, these data indicate that Snail2 and Snail1 cooperate for VDR repression in colon cancer. ; Ministerio de Ciencia e Innovación (SAF2007-60341, ISCIII-RETIC RD06/0020/0009); Comunidad de Madrid (S-GEN-0266-2006); European Union (MRTN-CT-2005-019496, NucSys). ; Peer Reviewed

16 pages, 11 figures. ; The active vitamin D metabolite 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3] has wide but not fully understood antitumor activity. A previous transcriptomic analysis of 1α,25(OH)2D3 action on human colon cancer cells revealed cystatin D (CST5), which encodes an inhibitor of several cysteine proteases of the cathepsin family, as a candidate target gene. Here we report that 1α,25(OH)2D3 induced vitamin D receptor (VDR) binding to, and activation of, the CST5 promoter and increased CST5 RNA and protein levels in human colon cancer cells. In cells lacking endogenous cystatin D, ectopic cystatin D expression inhibited both proliferation in vitro and xenograft tumor growth in vivo. Furthermore, cystatin D inhibited migration and anchorage-independent growth, antagonized the Wnt/β-catenin signaling pathway, and repressed c-MYC expression. Cystatin D repressed expression of the epithelial-mesenchymal transition inducers SNAI1, SNAI2, ZEB1, and ZEB2 and, conversely, induced E-cadherin and other adhesion proteins. CST5 knockdown using shRNA abrogated the antiproliferative effect of 1α,25(OH)2D3, attenuated E-cadherin expression, and increased c-MYC expression. In human colorectal tumors, expression of cystatin D correlated with expression of VDR and E-cadherin, and loss of cystatin D correlated with poor tumor differentiation. Based on these data, we propose that CST5 has tumor suppressor activity that may contribute to the antitumoral action of 1α,25(OH)2D3 in colon cancer. ; This work was supported by the Ministerio de Ciencia e Innovación (SAF2007-60341, SAF2006-00476, ISCIII-RETIC RD06/0020/0009, and RD06/0020/0020), Comunidad de Madrid (S-GEN-0266/2006), and the European Union (MRTN-CT-2005-019496, NucSys and Micoenvimet, FP7). The Instituto Universitario de Oncología and Hospital Universitario Central de Asturias tumor bank are supported by Obra Social Cajastur and Acción Transversal del Cáncer–RTICC. ; Peer reviewed