On the efficiency of flat slabs strengthening against punching using externally bonded fibre reinforced polymers

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Abstract

One possibility for strengthening existing flat slabs consists on gluing fibre reinforced polymers (FRPs) at the concrete surface. When applied on top of slab–column connections, this technique allows increasing the flexural stiffness and strength of the slab as well as its punching strength. Nevertheless, the higher punching strength is associated to a reduction on the deformation capacity of the slab–column connection, which can be detrimental for the overall behaviour of the structure (leading to a more brittle behaviour of the system). Design approaches for this strengthening technique are usually based on empirical formulas calibrated on the basis of the tests performed on isolated test specimens. However, some significant topics as the reduction on the deformation capacity or the influence of the whole slab (accounting for the reinforcement at mid-span) on the efficiency of the strengthening are neglected. In this paper, a critical review of this technique for strengthening against punching shear is investigated on the basis of the physical model proposed by the Critical Shear Crack Theory (CSCT). This approach allows taking into account the amount, layout and mechanical behaviour of the bonded FRP’s in a consistent manner to estimate the punching strength and deformation capacity of strengthened slabs. The approach is first used to predict the punching strength of available test data, showing a good agreement. Then, it is applied in order to investigate strengthened continuous slabs, considering moment redistribution after concrete cracking and reinforcement yielding. This latter study provides valuable information regarding the differences between the behaviour of isolated test specimens and real strengthened flat slabs. The results show that empirical formulas calibrated on isolated specimens may overestimate the actual performance of FRP’s strengthening. Finally, taking advantage of the physical model of the CSCT, the effect of the construction sequence on the punching shear strength is also evaluated, revealing the role of this issue which is also neglected in most empirical approaches.
Original languageUnknown
Pages (from-to)366-377
JournalConstruction and Building Materials
Volume73
Issue numberNA
DOIs
Publication statusPublished - 1 Jan 2014

Keywords

    Cite this

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    title = "On the efficiency of flat slabs strengthening against punching using externally bonded fibre reinforced polymers",
    abstract = "One possibility for strengthening existing flat slabs consists on gluing fibre reinforced polymers (FRPs) at the concrete surface. When applied on top of slab–column connections, this technique allows increasing the flexural stiffness and strength of the slab as well as its punching strength. Nevertheless, the higher punching strength is associated to a reduction on the deformation capacity of the slab–column connection, which can be detrimental for the overall behaviour of the structure (leading to a more brittle behaviour of the system). Design approaches for this strengthening technique are usually based on empirical formulas calibrated on the basis of the tests performed on isolated test specimens. However, some significant topics as the reduction on the deformation capacity or the influence of the whole slab (accounting for the reinforcement at mid-span) on the efficiency of the strengthening are neglected. In this paper, a critical review of this technique for strengthening against punching shear is investigated on the basis of the physical model proposed by the Critical Shear Crack Theory (CSCT). This approach allows taking into account the amount, layout and mechanical behaviour of the bonded FRP’s in a consistent manner to estimate the punching strength and deformation capacity of strengthened slabs. The approach is first used to predict the punching strength of available test data, showing a good agreement. Then, it is applied in order to investigate strengthened continuous slabs, considering moment redistribution after concrete cracking and reinforcement yielding. This latter study provides valuable information regarding the differences between the behaviour of isolated test specimens and real strengthened flat slabs. The results show that empirical formulas calibrated on isolated specimens may overestimate the actual performance of FRP’s strengthening. Finally, taking advantage of the physical model of the CSCT, the effect of the construction sequence on the punching shear strength is also evaluated, revealing the role of this issue which is also neglected in most empirical approaches.",
    keywords = "Internal forces redistribution, Continuous slabs, Construction sequence, Flat slabs, Critical Shear Crack Theory, Fibre reinforced polymer strengthening, Punching shear",
    author = "Ramos, {Ant{\'o}nio Manuel Pinho}",
    year = "2014",
    month = "1",
    day = "1",
    doi = "10.1016/j.conbuildmat.2014.09.084",
    language = "Unknown",
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    pages = "366--377",
    journal = "Construction and Building Materials",
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    T1 - On the efficiency of flat slabs strengthening against punching using externally bonded fibre reinforced polymers

    AU - Ramos, António Manuel Pinho

    PY - 2014/1/1

    Y1 - 2014/1/1

    N2 - One possibility for strengthening existing flat slabs consists on gluing fibre reinforced polymers (FRPs) at the concrete surface. When applied on top of slab–column connections, this technique allows increasing the flexural stiffness and strength of the slab as well as its punching strength. Nevertheless, the higher punching strength is associated to a reduction on the deformation capacity of the slab–column connection, which can be detrimental for the overall behaviour of the structure (leading to a more brittle behaviour of the system). Design approaches for this strengthening technique are usually based on empirical formulas calibrated on the basis of the tests performed on isolated test specimens. However, some significant topics as the reduction on the deformation capacity or the influence of the whole slab (accounting for the reinforcement at mid-span) on the efficiency of the strengthening are neglected. In this paper, a critical review of this technique for strengthening against punching shear is investigated on the basis of the physical model proposed by the Critical Shear Crack Theory (CSCT). This approach allows taking into account the amount, layout and mechanical behaviour of the bonded FRP’s in a consistent manner to estimate the punching strength and deformation capacity of strengthened slabs. The approach is first used to predict the punching strength of available test data, showing a good agreement. Then, it is applied in order to investigate strengthened continuous slabs, considering moment redistribution after concrete cracking and reinforcement yielding. This latter study provides valuable information regarding the differences between the behaviour of isolated test specimens and real strengthened flat slabs. The results show that empirical formulas calibrated on isolated specimens may overestimate the actual performance of FRP’s strengthening. Finally, taking advantage of the physical model of the CSCT, the effect of the construction sequence on the punching shear strength is also evaluated, revealing the role of this issue which is also neglected in most empirical approaches.

    AB - One possibility for strengthening existing flat slabs consists on gluing fibre reinforced polymers (FRPs) at the concrete surface. When applied on top of slab–column connections, this technique allows increasing the flexural stiffness and strength of the slab as well as its punching strength. Nevertheless, the higher punching strength is associated to a reduction on the deformation capacity of the slab–column connection, which can be detrimental for the overall behaviour of the structure (leading to a more brittle behaviour of the system). Design approaches for this strengthening technique are usually based on empirical formulas calibrated on the basis of the tests performed on isolated test specimens. However, some significant topics as the reduction on the deformation capacity or the influence of the whole slab (accounting for the reinforcement at mid-span) on the efficiency of the strengthening are neglected. In this paper, a critical review of this technique for strengthening against punching shear is investigated on the basis of the physical model proposed by the Critical Shear Crack Theory (CSCT). This approach allows taking into account the amount, layout and mechanical behaviour of the bonded FRP’s in a consistent manner to estimate the punching strength and deformation capacity of strengthened slabs. The approach is first used to predict the punching strength of available test data, showing a good agreement. Then, it is applied in order to investigate strengthened continuous slabs, considering moment redistribution after concrete cracking and reinforcement yielding. This latter study provides valuable information regarding the differences between the behaviour of isolated test specimens and real strengthened flat slabs. The results show that empirical formulas calibrated on isolated specimens may overestimate the actual performance of FRP’s strengthening. Finally, taking advantage of the physical model of the CSCT, the effect of the construction sequence on the punching shear strength is also evaluated, revealing the role of this issue which is also neglected in most empirical approaches.

    KW - Internal forces redistribution

    KW - Continuous slabs

    KW - Construction sequence

    KW - Flat slabs

    KW - Critical Shear Crack Theory

    KW - Fibre reinforced polymer strengthening

    KW - Punching shear

    U2 - 10.1016/j.conbuildmat.2014.09.084

    DO - 10.1016/j.conbuildmat.2014.09.084

    M3 - Article

    VL - 73

    SP - 366

    EP - 377

    JO - Construction and Building Materials

    JF - Construction and Building Materials

    SN - 0950-0618

    IS - NA

    ER -