in situ experimental tests on masonry panels strengthened with textile reinforced mortar composites

Abstract Textile Reinforced Mortar (TRM) composites are a retrofitting techniques used for strengthening masonry structures. The system is composed of dry fibers grids embedded in two layers of inorganic matrix. The paper describes the results of an in-situ experimental campaign on ancient masonry panels reinforced with different TRM systems. The tests were performed in a building located in Finale Emilia (north of Italy) built at the beginning of the last century. Four diagonal compressive tests were performed on unreinforced and reinforced walls. The walls were strengthened with different configurations: two panels were reinforced with a TRM systems composed of a lime mortar and two different types of glass fiber grids and twist steel bars used as anchors; one panel was reinforced with a layer of TRM on one side and a Near Surface Mounted (NSM) system on the other one. The results of the tests are described and a complete mechanical characterization of the reinforcement systems and of the masonry was performed to analyze the experimental results and validate simple analytical models

new italian guidelines for design of externally bonded fabric reinforced cementitious matrix frcm systems for repair and strengthening of masonry and concrete structures

Abstract The paper summarizes the main features of a standardization activity carried out in Italy by the Ministry of Public Works, to which two of the authors have taken part, for the homologation and the acceptance of Fabric-Reinforced Cementitious Matrix (FRCM) composites. During the last years, such composite materials have becoming increseangly popular in the civil engineering field for strengthening existing constructions, even if difficulties can occur in their mechanical characterization that is strongly affected by different and complex failure mechanisms. The American ACI 549.4R-13 is currently the only available guideline for design and construction of these systems. In this framework, the paper describes the Italian proposals for the homologation process of FRCM materials as well as for the design of strengthening interventions with these composites. Comparisons with the American guideline are also reported together with some considerations regarding the different partial safety factors

Ancient masonry arches and vaults strengthened with TRM, SRG and FRP composites: Numerical analyses

[EN] The two arches and the three vaults experimentally described in Carozzi et al. (2017) are here analyzed with a novel robust FE lower bound limit analysis code, suitable to predict active failure mechanisms, lines of thrust and collapse loads in absence and presence of TRM, SRG and FRP reinforcement. The approach relies into a discretization into rigid-infinitely resistant quadrilateral elements for masonry, interfaces between contiguous elements exhibiting limited strength and perfectly bonded rigid-plastic trusses representing the reinforcement. For masonry, a No Tension Material NTM model can be adopted to compare with classic Heyman¿s results, but also a limited compressive and tensile strength with a cohesive frictional behavior in shear may be accounted for in a relatively simple fashion, i.e. in principle with the possibility to model shear sliding and compression crushing. Debonding and delamination of the reinforcement are considered in a conventional way, assuming trusses with a limited tensile strength derived from either experimental data available or consolidated formulas from the literature. With the knowledge of the exact position of the hinges provided by limit analysis, 2D FE static analyses with non-linearity and softening concentrated exclusively on hinges are carried out, to simply extend the knowledge beyond collapse loads estimation towards a prediction of initial stiffness and ultimate displacements. In all cases, promising agreement with experiments is observed.Part of the analyses were developed within the activities of Rete dei Laboratori Universitari di Ingegneria Sismica - ReLUIS for the research program funded by the Dipartimento di Protezione Civile.Bertolesi, E.; Milani, G.; Carozzi, FG.; Poggi, C. (2018). Ancient masonry arches and vaults strengthened with TRM, SRG and FRP composites: Numerical analyses. Composite Structures. 187:385-402. https://doi.org/10.1016/j.compstruct.2017.12.021S38540218

Multimodal lung cancer screening using the ITALUNG Biomarker Panel and Low Dose Computed Tomography. Results of the ITALUNG biomarker study

Asymptomatic high-risk subjects, randomized in the intervention arm of the ITALUNG trial (1406 screened for lung cancer), were enrolled for the ITALUNG biomarker study (n = 1356), in which samples of blood and sputum were analysed for plasma DNA quantification (cut off 5ng/ml), loss of heterozygosity and microsatellite instability. The ITALUNG biomarker panel (IBP) was considered positive if at least one of the two biomarkers included in the panel was positive. Subjects with and without lung cancer diagnosis at the end of the screening cycle with LDCT (n = 517) were evaluated. Out of 18 baseline screen detected lung cancer cases, 17 were IBP positive (94%). Repeat screen-detected lung cancer cases were 18 and 12 of them positive at baseline IBP test (66%). Interval cancer cases (2-years) and biomarker tests after a suspect Non Calcific Nodule follow-up were investigated. The single test versus multimodal screening measures of accuracy were compared in a simulation within the screened ITALUNG intervention arm, considering screen-detected and interval cancer cases. Sensitivity was 90% at baseline screening. Specificity was 71%% and 61% for LDCT and IBP as baseline single test, and improved at 89% with multimodal, combined screening. The positive predictive value was 4.3% for LDCT at baseline and 10.6% for multimodal screening. Multimodal screening could improve the screening efficiency at baseline and strategies for future implementation are discussed. If IBP was used as primary screening test, the LDCT burden might decrease of about 60%

Calibration of end-debonding strength model for FRP-reinforced masonry

The adherence between Fiber Reinforced Polymers (FRP) reinforcements and masonry is investigated in this paper. Debonding is, in fact, one of the dominant failure modes in the reinforcement of masonry structures by means of FRP materials. Relationships are proposed in design recommendations in order to evaluate the debonding load on the basis of the fracture energy concept. Corrective coefficients are also suggested in order to take into account the effect of bond length and width on the bond strength. In this work experimental double lap push-pull shear tests results are first presented and combined with experimental outcomes from the literature in order to create an enlarged database. An analytical model for the load transfer mechanism between the reinforcement and the substrate is then proposed. Besides, a refined fracture energy based model for the bond strength is suggested taking into account the effect of bond length and width. The experimental outcomes are first used to validate the analytical model for the load transfer mechanism. The enlarged database is then analyzed to achieve a refined statistical calibration of the experimental coefficients of the bond strength model and to highlight the variation of the maximum transmitted force with respect to mechanical properties of the substrate

Mechanical and bond properties of FRP anchor spikes in concrete and masonry blocks

Fibre Reinforced Polymer (FRP) materials are extensively used to retrofit masonry and reinforced concrete structures. Failure occurs in most cases due to composite debonding from the substrate. The use of FRP anchor spikes was thus proposed to reduce premature debonding failure. In this work, the results of an extensive experimental program on the bond behaviour between the FRP anchor spikes and the substrate are first presented. They include both the mechanical characterization of carbon and glass FRP anchor spikes and pull-out tests from concrete and masonry blocks. In pull-out specimens, FRP anchor spikes are embedded into the block (embedded anchor spikes) or fanned-out on the substrate surface (fanned-out anchor spikes) with an epoxy resin. For different specimen configurations and materials, the bond behaviour of the FRP anchor is analysed. The mostly observed failure modes were the tensile failure of the anchor spikes, the debonding of the anchor spikes from the substrate or a combination of both. Nonlinear finite element simulations were finally performed to understand the bond behaviour between FRP anchors spikes and concrete substrate