On Minimum Reinforcement in Concrete Structures

Levi, F. A.

doi:10.1061/(asce)0733-9445(1985)111:12(2791)

Cited by 17 publications

(5 citation statements)

References 1 publication

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“…In particular, for lightly reinforced concrete structures, this model has to be used together with that already introduced by (Chiaia et al) [1] for the evaluation of the minimum amount of steel rebars. In fact, according to (Levi) [11], the criteria used to establish the minimum reinforcement percentages may regard both the ultimate limit state of the structure (i.e. the reinforcement must be dimensioned so that at the onset of cracking, the tensile stresses acting on the rebars will be prevented from exceeding the elastic limit of steel) and the serviceability conditions (i.e.…”

Section: Introductionmentioning

confidence: 99%

Crack Patterns in Reinforced and Fiber Reinforced Concrete Structures

Chiaia¹,

Fantilli²,

Vallini³

2008

TOBCTJ

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The cracking phenomenon of members made of traditional reinforced concrete (RC) or by combining steel fibers and traditional reinforcing bars (R/FRC) is analyzed in this paper. Referring to the tensile zone of a beam subjected to bending moment and axial load, a unique block model is introduced to predict crack widths, crack lengths and crack distances. The proposed approach, based on the nonlinear behaviour of the cracked cement-based material in tension, and on the bond-slip interaction between rebars and concrete, provides crack patterns similar to those observed in different experimental campaigns. Cracks in R/FRC beams are generally narrower, and originate at small distances, than those observed in RC beams having the same geometry and reinforcement ratio. This is entirely due to the presence of fibers, here considered through the Reinforcing Index, which is the product of volume percentage and fiber aspect ratio. However, the beneficial effect of fiber-reinforcement vanishes with the increase of structural dimension. Thus, in the case of massive structures, it appears necessary a direct calculation of the crack width, even in the presence of fibers.

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Section: Introductionmentioning

confidence: 99%

Crack Patterns in Reinforced and Fiber Reinforced Concrete Structures

Chiaia¹,

Fantilli²,

Vallini³

2008

TOBCTJ

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“…This should guarantees a ductile behaviour of the segment provided by the fibres in the event of cracking (Chiaia et al, 2009a,b;Fantilli et al, 2016a,b). Such procedure is consistent with the safety format and ductility requirements used for traditional reinforced concrete (Levi 1985). A reliability analysis was performed to calibrate the partial safety factor applied to f R in the design of transient loading situations of FRC segments subjected to bending.…”

Section: Procedures and Assumptionsmentioning

confidence: 99%

Safety format for the flexural design of tunnel fibre reinforced concrete precast segmental linings

Cugat

Cavalaro

Bairán

et al. 2020

Tunnelling and Underground Space Technology

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Fibre reinforced concrete (FRC) is increasingly used in tunnel segmental linings constructed with tunnel boring machines. Several codes include the FRC as a structural material and specific guidelines cover the design of FRC precast segmental linings. All of these consider the traditional limit state format, applying partial safety factors to the loads (γ L ) and material strengths (γ M ). Often, the γ M applied to the residual tensile strength of FRC is assumed the same as for concrete in compression. However, the variability in the determination of the residual tensile strength may be several times bigger than that of the compressive strength. In this context, the application of the same γ M should be revised as it could lead to reliability indexes lower than the established for traditional reinforced concrete structures. The objective of this paper is to estimate safety factors for the residual flexural response of FRC used in tunnels segments, considering the variability of the material in both the material characterisation test and in the real-scale structure. After a study about the influence of the element size on the variability, an evaluation of the structural reliability of the segmental linings made with FRC is performed using the FORM method and a database of real-scale test results compiled from existing literature. Based on that, values of γ M are proposed according to different failure consequences levels and relative economic costs required to increase the structural safety.

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“…The moment-curvature diagram (M -χ) presented in Figure 2b includes different reinforcement configurations (infracritical, critical and supracritical) [23]. Notice that by imposing M u ≥ M cr , only critical and supracritical reinforcement configurations are allowed according to the design philosophy from the MC 2010.…”

Section: Design Procedures Based On the MC 2010mentioning

confidence: 99%

Design of FRC tunnel segments considering the ductility requirements of the Model Code 2010

Fuente

Cavalaro

et al. 2015

Tunnelling and Underground Space Technology

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Fibre reinforced concrete (FRC) is used to improve the mechanical response of precast segments for tunnels. The structural use of the material has been regulated by national codes and, recently, by the Model Code 2010 (MC 2010, hereinafter). In this regard, it is necessary to update the philosophy applied to the design of tunnel segments in compliance with the most recent guidelines, evaluating their applicability and repercussion. The objective of this paper is to present a critical analysis of the design of FRC segments according to the ductility requirements from the MC 2010; an alternative approach is proposed that is compatible with the condition found in some tunnels. The repercussions of both approaches are evaluated for the Metro Line 9 from Barcelona using results obtained in an experimental program with full-scale segments. The study suggests that the alternative approach may be applied under certain conditions, leading to a reduction in the fibre consumption. Keywords: Barcelona Metro Line, Cracking bending moment, design, ductility, FRC, precast segments.Tunnelling and Underground Space Technology 2 INTRODUCTIONFibre reinforced concrete (FRC) is a composite material used to improve the mechanical response of precast segments for tunnels [1][2][3][4], enhancing their ductility and fire resistance as well as their mechanical performance during transient load stages. Due to these advantages, the use of structural fibres contributes to the replacement of traditional passive reinforcement, accelerating the production process and increasing the competitiveness of the FRC. Proof of this are the numerous experiences in which precast FRC segments have been used in highway (RT), railway (RWT), metro (MT), water supply (WTT), gas transport (GPT) and service (ST) tunnels. Table 1 [4][5][6] summarizes some of the main applications already in service or under construction.The structural use of fibres has been regulated by the national codes in Germany in 1992 [7], Italy in 2006 [8] and Spain in 2008 [9], for instance. More recently, recommendations about the design of FRC structures were also included in the MC 2010 [10], with constitutive equations [11][12] and models for the Service Limit State and Ultimate Limit State (SLS and the ULS, respectively). An increase in the use of FRC in tunnels segments has been observed as a result of that [13]. In this regard, it is necessary to update the philosophy applied to the design of tunnel segments in compliance with the particular requirements proposed in the MC 2010, evaluating its applicability and repercussions.The objective of this paper is to present a critical analysis of the design of FRC segments according to the ductility requirements from the MC 2010 and to propose an alternative approach more compatible with the conditions found in practice. First, the design procedure from the MC 2010 is analysed and adapted to FRC segmented linings. Then, the alternative approach is presented. The applicability and repercussion of both approaches in terms of fibre ...

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On Minimum Reinforcement in Concrete Structures

Cited by 17 publications

References 1 publication

Crack Patterns in Reinforced and Fiber Reinforced Concrete Structures

Crack Patterns in Reinforced and Fiber Reinforced Concrete Structures

Safety format for the flexural design of tunnel fibre reinforced concrete precast segmental linings

Design of FRC tunnel segments considering the ductility requirements of the Model Code 2010

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