Intermediate Debonding in Frp Strengthened RC Beams: a Numerical Model

One of the most effective ways for improving the flexural strength of RC members consists in bonding FRP laminates at their soffit in order to upgrade the existing tensile strength. Strengthening RC beams by Externally Bonded FRP laminates is getting more and more common and various Codes of Standards have been issued in Europe, United States and Japan. In particular, the most up-to-date document has been released in Italy one year ago. A key problem to be faced when managing FRP strengthened beams deals with the possible premature failure due to debonding between the adhesive layer and concrete, which can occur at the beam end (end debonding) or in the cracked zone (intermediate debonding). In the present paper, a mechanical model considering non-linear stress-strain relationships for concrete, steel and FRP-to-concrete interface is presented, with the aim of simulating the behavior of RC beams strengthened by externally bonded FRP plates

Behavior and Strengthening of RC Beam-Column Joints: Experimental Program and First Results of the Research Activity in the Framework of DPC-ReLUIS Project (Research Line 2)

The 2005-2008 DPC-Reluis Project, funded by the Italian Department of Civil Protection (DPC), is made up of ten Research Lines (RL). RL 2 specifically focuses on the seismic performance of existing RC buildings and is, in turn, organised in nine different Tasks. In the paper, the design of the research activities being carried out within the Task 7 by the four involved Research Units (RU UNIBAS, RU UNIUD, RU UNISA, and RU UNINA) and some first results are reported. Main objective of Task 7 is to investigate on the experimental behaviour of beam-column joints without or with strengthening, thus providing a contribution to a more reliable evaluation of the seismic vulnerability of Reinforced Concrete existing buildings. To this purpose the main activities carried out have been devoted to design and set up of wide experimental programs on beam-column joints relevant to typical existing RC buildings having different Earthquake Resistant Design (ERD) level, to make a literature review of the state of the art on the subject, to perform numerical simulations based on some analytical models available in literature in order to fully understand the mechanical behaviour. Further, some results of the tests already carried out are reported, analysed and compared in order to understand the failure mechanism and evaluate the seismic performance of joints with and without ERD

Salt-Induced Deterioration on FRP-Brick Masonry Bond

In the past decades, several studies have shown how fiber reinforced polymer (FRP) composites are an effective technique to strengthen unreinforced brick masonry structures. However, very little is known about their durability against environmental aggression such as salt attack and freeze-thaw cycles, or elevated moisture content. This paper presents an investigation on influence of salt attack on the stress transfer between the FRP composite and the masonry substrate. In fact, it is well known that, in certain conditions, soluble salts crystallize within the pores of materials, leading to crystallization pressures that may overcome their tensile strength. To investigate this effect, FRP-masonry joints were subjected to salt crystallization cycles according to a conditioning procedure designed by the authors. After conditioning, direct shear tests were conducted on the masonry joints to investigate the interfacial bond between the substrate and the composite. Materials characterization was carried out in order correlate the results of the direct shear tests with the salt distribution within the specimens. For comparison, direct shear tests were conducted on FRP-masonry joints that were not subjected to any cycle and therefore used as control

Non-Zero Sum Games for Reactive Synthesis

In this invited contribution, we summarize new solution concepts useful for the synthesis of reactive systems that we have introduced in several recent publications. These solution concepts are developed in the context of non-zero sum games played on graphs. They are part of the contributions obtained in the inVEST project funded by the European Research Council.Comment: LATA'16 invited pape

Hygrothermal durability of bond in FRP-strengthened masonry

Fiber reinforced polymers (FRPs) are accepted as an efficient material for external strengthening of masonry structures. Previous researches have shown that the bond between FRP and the substrate plays an important role in the effectiveness of this strengthening technique. Extensive investigations have been devoted to the characterization of the short-term bond behavior, while its durability and long-term performance requires further studies. In this regard, a full experimental program for investigating the environmental durability of bond in FRP-strengthened masonry is crucial for understanding the degrading mechanisms. This paper presents the results of an experimental program aimed at investigating the hygrothermal durability of bond in FRP-strengthened bricks. Accelerated ageing tests were performed on the FRP-strengthened brick elements and the bond degradation was periodically investigated by visual inspection and by conventional single-lap shear bond tests. The changes in the properties of material constituents have also been monitored. The obtained results are presented and critically discussed.This work was developed within the framework of the RILEM Technical Committee "223-MSC: Masonry Strengthening with Composite Materials". The financial support from the project FP7-ENV-2009-1-244123-NIKER of the 7th Framework Program of the European Commission is gratefully acknowledged. The first author also acknowledges the financial support of the Portuguese Science Foundation (Fundacao de Ciencia e Tecnologia, FCT), through grant SFRH/BD/80697/2011

Modelling distributions of Aedes aegypti and Aedes albopictus using climate, host density and interspecies competition.

Florida faces the challenge of repeated introduction and autochthonous transmission of arboviruses transmitted by Aedes aegypti and Aedes albopictus. Empirically-based predictive models of the spatial distribution of these species would aid surveillance and vector control efforts. To predict the occurrence and abundance of these species, we fit a mixed-effects zero-inflated negative binomial regression to a mosquito surveillance dataset with records from more than 200,000 trap days, representative of 53% of the land area and ranging from 2004 to 2018 in Florida. We found an asymmetrical competitive interaction between adult populations of Aedes aegypti and Aedes albopictus for the sampled sites. Wind speed was negatively associated with the occurrence and abundance of both vectors. Our model predictions show high accuracy (72.9% to 94.5%) in validation tests leaving out a random 10% subset of sites and data since 2017, suggesting a potential for predicting the distribution of the two Aedes vectors

SPIRITS: Uncovering Unusual Infrared Transients with Spitzer

We present an ongoing, five-year systematic search for extragalactic infrared transients, dubbed SPIRITS—SPitzer InfraRed Intensive Transients Survey. In the first year, using Spitzer/IRAC, we searched 190 nearby galaxies with cadence baselines of one month and six months. We discovered over 1958 variables and 43 transients. Here, we describe the survey design and highlight 14 unusual infrared transients with no optical counterparts to deep limits, which we refer to as SPRITEs (eSPecially Red Intermediate-luminosity Transient Events). SPRITEs are in the infrared luminosity gap between novae and supernovae, with [4.5] absolute magnitudes between −11 and −14 (Vega-mag) and [3.6]–[4.5] colors between 0.3 mag and 1.6 mag. The photometric evolution of SPRITEs is diverse, ranging from 7 mag yr−1. SPRITEs occur in star-forming galaxies. We present an in-depth study of one of them, SPIRITS 14ajc in Messier 83, which shows shock-excited molecular hydrogen emission. This shock may have been triggered by the dynamic decay of a non-hierarchical system of massive stars that led to either the formation of a binary or a protostellar merger