Rotational model for the determination of the shear capacity of reinforced and prestressed concrete structures

Asko Sarja, Pekka Nykyri

Research output: Book/ReportReport


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 languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages19
ISBN (Print)951-38-1469-6
Publication statusPublished - 1982
MoE publication typeD4 Published development or research report or study

Publication series

SeriesValtion teknillinen tutkimuskeskus. Tutkimuksia - Research Reports


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