Elevated slabs made of hybrid reinforced concrete: Proposal of a new design approach in flexure

Facconi, Luca; Plizzari, Giovanni; Minelli, Fausto

doi:10.1002/suco.201700278

Cited by 28 publications

(24 citation statements)

References 26 publications

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“…• ductility requirements often impose the presence of conventional reinforcement, especially in linear [40] elements but also in elevated slabs; rebars may take additional stresses due to FRC creep that are negligible in most cases. • When FRC is adopted for substituting secondary reinforcement for stress redistribution, creep has a minor influence since FRC is not necessary for equilibrium.…”

Section: Discussionmentioning

confidence: 99%

“…Other cases that are of increasing interest in recent years are elevated two-ways slabs [39,40], due to the smaller reinforcement ratio needed. Here fibers can substitute most of the traditional reinforcement and, due to the high degree of redundancy, these structures allow a significant stress redistribution.…”

Section: Shear In Linear Elements With Rebars As Bending Reinforcementmentioning

confidence: 99%

“…3 and 4) for the expected failure mode, as slabs are very stiff structures and then deformability is usually low. Therefore, a minimum ''anti-collapse'' reinforcement is generally present along the lines connection columns; recent studies clearly evidenced that an optimized reinforcement requires the addition of further rebars to provide resistance to peak moments present on the columns [40] (Fig. 7).…”

Section: Shear In Linear Elements With Rebars As Bending Reinforcementmentioning

confidence: 99%

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Structural effects of FRC creep

Plizzari

Ros

2018

Mater Struct

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Research studies in the last 20 years allowed to obtain reliable rules for designing structures made of fiber reinforced concrete (FRC). However, design aspects like the long-term behavior of FRC, especially when synthetic fibers are adopted, require further research. Long-term behavior includes aging and creep. Aging represent the change of fiber properties into the concrete environment, which may reduce the structural bearing capacity; when present, it is an important issue for the structural safety, especially when fibers are the only reinforcement. Aging of fibers must be proven by experimental tests. Creep is a complex phenomenon, roughly considered by building codes even for traditional reinforced concrete (RC) structures. The introduction of fibers do not change anything in concrete matrix and, before cracking, in the material concrete creep behavior is not expected any change. After cracking, the structural effect of FRC creep depends on the degree of structural redundancy and on the presence of rebars since creep produces a stress redistribution in the structure or from FRC to the rebars. When FRC postcracking resistance is necessary for equilibrium requirements, in structures with cracked sections in service conditions the structural deferred response has to be analyzed by considering the FRC creep behavior. When FRC is used for resisting secondary actions and rebars are present for equilibrium requirements, the response of a FRC element (with rebars and fibers) will be identical to a conventional RC; FRC contributes by controlling the crack development under both short and long term loading.

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Section: Discussionmentioning

confidence: 99%

Section: Shear In Linear Elements With Rebars As Bending Reinforcementmentioning

confidence: 99%

Section: Shear In Linear Elements With Rebars As Bending Reinforcementmentioning

confidence: 99%

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Structural effects of FRC creep

Plizzari

Ros

2018

Mater Struct

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“…However, field applications of UHPC are still limited since the preparation of UHPC normally requires high fiber volume fraction (≥2%) and fine powders, which leads to complexity in preparation, construction and high costs 8 . In addition, if steel fibers are used as the sole or primary reinforcement, significantly increased fiber dosage will be required in the whole structure to resist high stresses acting only in localized areas 5 . As a result, hybrid reinforced UHPC containing steel bars and fibers are being studied and applied to obtain efficient structural performance with reduced fiber contents.…”

Section: Introductionmentioning

confidence: 99%

Analytical approach for the design of flexural elements made of reinforced ultra‐high performance concrete

Yao

Mobasher

Wang

et al. 2020

Structural Concrete

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The increasing demands of sustainable design and construction with economical sections, reduced cover, and more efficient time schedule require more flexibility in the design methodologies. The development of ultra‐high performance concrete (UHPC) have gained increasing interests as an attractive option for structural members with lightweight and superior performances. Concrete members reinforced with steel bars and fibers, generally known as hybrid reinforced concrete (HRC), offer a feasible solution in terms of reducing reinforcing materials and achieving desired structural performance. This paper proposes an analytical model to predict the flexural behavior of hybrid reinforced UHPC with steel reinforcements. Moment–curvature solutions are derived for reinforced sections based on parameterized tension‐compression constitutive models. The approach is applicable to customized cross section and derivation of T‐section is demonstrated. The moment–curvature response is further simplified as a tri‐linear model, which is used for the development of full‐range displacement solutions in analytical form. The proposed model is validated with the experimental data from literature covering a range of materials and member sizes. The full‐range solutions may provide insights into the serviceability design approach based on the criterion of maximum crack width or allowable deflection.

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“…The improvement of the tensile behavior of concrete due to the use of fibers can be exploited to enhance the ultimate and the serviceability performance of different kinds of structures [19]. Several research studies have proven the ability of fibers to partially or even totally replace conventional steel reinforcement in structures characterized by a significantly high degree of redundancy, such as slab-on-grade and elevated slabs [20]. Other authors have shown the possibility of partially replacing either the flexural or the shear reinforcement in concrete beams [21].…”

Section: Introductionmentioning

confidence: 99%

Experimental Tests on Fiber-Reinforced Alkali-Activated Concrete Beams Under Flexure: Some Considerations on the Behavior at Ultimate and Serviceability Conditions

2019

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Alkali-activated concrete (AAC) is an alternative concrete typology whose innovative feature, compared to ordinary concrete, is represented by the use of fly ash as a total replacement of Portland cement. Fly ash combined with an alkaline solution and cured at high temperature reacts to form a geopolymeric binder. The growing interest in using AACs for structural applications comes from the need of reducing the global demand of Portland cement, whose production is responsible for about 9% of global anthropogenic CO2 emissions. Some research studies carried out in the last few years have proved the ability of AAC to replace ordinary Portland cement concrete in different structural applications including the construction of beams and panels. On the contrary, few experimental results concerning the structural effectiveness of fiber-reinforced AAC are currently available. The present paper presents the results of an experimental program carried out to investigate the flexural behavior of full-scale AAC beams reinforced with conventional steel rebars, in combination with fibers uniformly spread within the concrete matrix. The experimental study included two beams containing 25 kg/m3 (0.3% in volume) of high-strength steel fibers and two beams reinforced with 3 kg/m3 (0.3% in volume) of synthetic fibers. A reference beam not containing fibers was also tested. The discussion of the experimental results focuses on some aspects significant for the structural behavior at ultimate limit states (ULS) and serviceability limit states (SLS). The discussion includes considerations on the flexural capacity and ductility of the test specimens. About the behavior at the SLS, the influence of fiber addition on the tension stiffening mechanism is discussed, together with the evolution of post-cracking stiffness and of the mean crack spacing. The latter is compared with the analytical predictions provided by different formulations developed over the past 40 years and adopted by European standards.

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Elevated slabs made of hybrid reinforced concrete: Proposal of a new design approach in flexure

Cited by 28 publications

References 26 publications

Structural effects of FRC creep

Structural effects of FRC creep

Analytical approach for the design of flexural elements made of reinforced ultra‐high performance concrete

Experimental Tests on Fiber-Reinforced Alkali-Activated Concrete Beams Under Flexure: Some Considerations on the Behavior at Ultimate and Serviceability Conditions

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