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Evaluating the new CAN/CSA-S806-12 torsion provisions for concrete beams with FRP reinforcements

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Abstract

Recently, the Canadian Standards Association proposed the first and only torsion design provisions for the case of beams with fiber reinforced polymer (FRP) reinforcements within the Canadian standard “Design and construction of building structures with fiber-reinforced polymers” (CAN/CSA-S806-12). The evaluation of the shear provisions of this code has shown more accurate and consistent shear predictions compared with other codes. The purpose of this study is to evaluate the torsion provisions of the CAN/CSA-S806-12. Such evaluation is performed considering the available experimental database from four different studies examining over 20 concrete beams with FRP or mixed (i.e. FRP and steel) reinforcements, tested under torsion. The cracking and ultimate torque as well as the failure mode predicted using the CAN/CSA-S806-12 were compared with the experimentally observed ones. The CAN/CSA-S806-12 was found to be overly conservative. Thus, modifications were proposed to the current CAN/CSA-S806-12, which were found to provide slightly better results.

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Abbreviations

ε L :

Longitudinal strain in the tensile reinforcements

Θ :

The angle of inclination of the diagonal compressive stress with respect to the longitudinal axis of the element

A c :

Total area of concrete cross section (mm2)

A L :

The longitudinal reinforcement resisting the torsion (mm2)

A o :

Enclosed area inside the shear flow path (mm2)

A oh :

Enclosed area inside the centerline of the outermost closed stirrup (mm2)

A t :

The area of transversal reinforcement resisting the torsion (mm2)

C :

Clear cover to the closed stirrup (mm)

E L :

Young’s Modulus of longitudinal reinforcement (MPa)

E steel :

Young’s modulus of steel taken as 200 GPa

E t :

Young’s modulus of transversal reinforcements in (MPa)

\(f^{\prime}_{\text{c}}\) :

Concrete compressive strength (MPa)

f Ft :

Design strength of the FRP bar which shall be less than 0.4 f Fu or 1200 (MPa)

f Fu :

Ultimate strength of the FRP bar which shall be less than 0.005E t in (MPa)

F lc :

Force carried by compressive longitudinal reinforcements (N)

F lt :

Force carried by tensile longitudinal reinforcements (N)

f y :

Yield stress of the steel reinforcements (MPa)

p c :

Perimeter of the concrete section (mm)

P h :

Perimeter of centerline of the outermost closed stirrup (mm)

S :

The spacing between stirrups (mm)

T:

The depth of the beam (mm)

T :

Ultimate torsional strength of the cross section (N mm)

T cr :

Cracking torsion of the cross section (N mm)

t w :

Wall thickness of idealized hollow section that is assumed to be not greater than either the ratio of A oh/p h or two times the minimum C (mm)

x :

The dimension of the short side of the cross section (mm)

y :

The dimension of the long side of the cross section (mm)

σ cr :

Concrete stress at cracking

α :

The stress torsion factor, which is calculated as the ratio between the T cr and the Σx 2 × y × σ cr term.

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Acknowledgments

The financial support of the Science and Technology Development Fund (STDF) of Egypt, Short Term Fellowship Project ID 6482 is gratefully acknowledged (Dr Ahmed Deifalla). In addition, valuable technical advice from Professor Rahal Khaldoun, University of Kuwait during the development of this paper is highly appreciated.

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Authors and Affiliations

  1. Department of Structural Engineering, Cairo University, Giza, Egypt

    M. M. Hassan

  2. Department of Civil Engineering, The Britisch University in Egypt, P.O. Box 43, El Shorouk City, 11837, Egypt

    A. Deifalla

  3. Institut für Angewandte Mechanik, Technische Universität Braunschweig, Bienroder Weg 87, 38106, Brunswick, Germany

    A. Deifalla

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  1. M. M. Hassan
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Correspondence to A. Deifalla.

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Hassan, M.M., Deifalla, A. Evaluating the new CAN/CSA-S806-12 torsion provisions for concrete beams with FRP reinforcements. Mater Struct 49, 2715–2729 (2016). https://doi.org/10.1617/s11527-015-0680-9

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  • DOI: https://doi.org/10.1617/s11527-015-0680-9

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