### Abstract

The main mode of shear failure of concrete beams and
slabs occurs, when the concrete has cracked and
reinforcement is no longer able to keep the concrete
blocks together or the concrete fails at the compression
side, when the structure becomes a mechanism and fails.
This failure occurs by rotation of the concrete blocks
between cracks.
The principle of the rotation calculation model treats
only the mode of failure just presented. In this
principle the rotational equilibrium at the crack of the
beam is studied. Here the estimation of the crack angle
is decisive. In this report, a new approach to the
approximative calculation of the crack angle is
presented. The formula for the crack angle is modelled as
a function of the structural shape of the cross section,
the ratio between shear force and bending moment and the
amount of shear reinforcement. The constants for the
approximative formula of the crack angle in the case of
prestressed structures have been determined here on the
basis of test results, including a wide variation range
of parameters. Other formulae needed in the practical
calculation of the shear capacity of prestressed concrete
structures have also been presented here.
When using this method the same calculation formulae can
be used for pure shear, for combined shear and bending
and for pure bending.
The results of the calculations in the case of
prestressed hollow core slabs and prestressed I-beams
have been compared to test results. The comparison shows
a close agreement between calculations and test results.
At the end of the report the main parts of the further
research program have been presented.

Original language | English |
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Place of Publication | Espoo |

Publisher | VTT Technical Research Centre of Finland |

Number of pages | 19 |

ISBN (Print) | 951-38-1469-6 |

Publication status | Published - 1982 |

MoE publication type | D4 Published development or research report or study |

### Publication series

Series | Valtion teknillinen tutkimuskeskus. Tutkimuksia - Research Reports |
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Number | 76 |

ISSN | 0358-5077 |

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## Cite this

Sarja, A., & Nykyri, P. (1982).

*Rotational model for the determination of the shear capacity of reinforced and prestressed concrete structures*. VTT Technical Research Centre of Finland. Valtion teknillinen tutkimuskeskus. Tutkimuksia - Research Reports, No. 76