1,721,153 research outputs found
Green public procurement applied to partially precast reinforced concete slabs
Full text linkTo build environmentally friendly public constructions, authorities impose tailoring concrete mixtures with a
minimum content of recycled materials. To satisfy this green public procurement (GPP) in frame structures,
whose mass is mainly distributed on horizontal diaphragms, it is necessary to draw attention to the slabs of
floors. As ready-mixed concrete with recycled materials is not easily available on the market, partially prefabricated
one-way slabs, composed by both cast-in-situ concrete and precast plates (generally called predalles)
were investigated. Only the precast concrete of predalles contained recycled materials, such as supplementary
cementitious materials (SCM) in place of CEM I, recycled concrete aggregate (RCA) and rubber to replace stone
aggregate, and recycled steel fibers (RSF). These materials were used to cast full-scale one-way slabs, subsequentially
tested in three-point bending. A three-stage model, based on the equivalence between the traditional
rebar and RSF, was also introduced to predict the load-deflection responses of the slabs. As results, both numerical
and experimental analyses revealed the effectiveness of RSF, which can be added to concrete mixtures to
compensate the loss of flexural strength that the substitution of virgin materials produces. Thus, if large quantities
of SCM, RCA, rubber, and RSF are in the concrete of predalles, slab can satisfy both GPP and the mechanical
performances, though the cast-in-situ concrete does not contain any recycled material
Ruolo dei meccanismi di aderenza e di frattura nella fase di esercizio degli elementi di conglomerato armato
No full textSul comportamento di elementi semplicemente tesi in conglomerato cementizio armato placcati
No full textOptimization of hybrid reinforcement in precast concrete linings using numerical analysis
No full textConcrete mixtures reinforced with a combination of steel rebar and fibers, i.e., Hybrid Reinforced Concretes (HRC), are frequently used in segmental precast tunnel linings. As massive cross-sections are usually adopted in these structures, only the minimum reinforcement is necessary to prevent the brittle failure. To study the brittle/ductile behavior of HRC tunnel segments in bending, the flexural responses of Lightly Reinforced Concrete (LRC) and that of Fiber-Reinforced Concrete (FRC) elements are modelled and combined herein. By means of this combination, the minimum reinforcement of HRC segments can be determined with a new design-by-testing procedure, in which the ductility index DI should be equal to zero. As a result, the minimum hybrid reinforcement can be defined through a linear combination of the minimum area of rebar and the minimum fiber volume fraction of LRC and FRC segments, respectively
Fiber volume fraction and ductility index in fiber-reinforced concrete round determined panels
No full textDue to the high scatter affecting the post-cracking response of Fiber-Reinforced Concrete Beams (FRC-B) in bending, new Fiber-Reinforced Concrete Round Determined Panels (FRC-RDP) are tested. Accordingly, the introduction of a model to predict the flexural response of FRC-RDP is of practical interest. Similarly to FRC-B, the response of centrally loaded FRC-RDP can be described by the Ductility Index (DI), which defines the deflection-softening or the deflection-hardening behavior. Since DI is proportional to the difference between ultimate and effective cracking loads, the brittle/ductile transition corresponds to DI equal to zero. Moreover, a linear increment of DI with the amount of fibers can be theoretically and experimentally found for both beams and panels. Through this general relationship, the minimum amount of fibers for ductile response can be determine
Tailoring HPFRC with materials from end of life tires HPFRC ottenuti con materiali provenienti dagli pneumatici a fine vita
No full textThe disposal of waste tires is a serious worldwide environmental issue, as the impact of construction industry,
which is the first consumer of raw materials. Accordingly, the main purpose of this article is to tailor High-Performance
Fiber-Reinforced Concrete (HPFRC) by using recycled steel fibers form end of life tires. The assessment of the
environmental impact and the mechanical behavior of different HPFRC mixtures is carried out through the Eco-Mechanical
index (EMI). By means of EMI, which allows to simultaneously displaying both ecological and mechanical properties,
it is possible to select the HPFRC with the best performances. In particular, it is possible to evaluate the content of
recycled fibers that can compensate the reduction of strength produced by the substitution of stone aggregates with rubber.
/ Lo smaltimento degli pneumatici a fine vita è un grave problema ambientale, come l'impatto dell'industria delle costruzioni, che è il
maggiore consumatore di materie prime. Di conseguenza, lo scopo principale di questo articolo è quello di introdurre un calcestruzzo
fibro-rinforzato ad alte prestazioni (HPFRC) utilizzando fibre di acciaio riciclate dei pneumatici fuori uso. La valutazione dell'impatto
ambientale e del comportamento meccanico delle diverse miscele di HPFRC viene effettuata tramite l'indice eco-meccanico (EMI).
Mediante l’EMI, che consente di visualizzare contemporaneamente le proprietà ecologiche e meccaniche, è possibile selezionare
l'HPFRC con le migliori prestazioni. In particolare, è possibile individuare il contenuto di fibre riciclate in grado di compensare la
riduzione della resistenza prodotta dalla sostituzione di aggregati di lapidei con gomma
The work of fracture in the eco-mechanical performances of structural concrete
No full textthe elastic approach of eco-mechanical performances of concrete is presented. In particular the fracture energy aspects are investigated, taking into account aggregates and fibre
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