### Abstract

Part I of the present thesis deals with crack formation in
reinforced concrete and the phenomenon of tension stiffening in
concrete tension rods reinforced with deformed bars.Two physical
models are presented for uniaxial tension, and they are modified
for application on beams subjected to pure flexure.In the first
model, the yield zone model, it is assumed that the mean crack
distance is a descending function of the reinforcement stress in a
crack. Furthermore it is assumed that in certain zones between the
cracks the concrete is carrying its full effective tensile
strength, i.e. the concrete is yielding.In the second model, the
concrete crack stress model, the mean crack distance is assumed to
be constant from the very initiation of cracking. In this model it
is assumed that there is a certain transmission of concrete
tensile stresses in the cracks.The stress-strain diagrams and mean
crack widths predicted by the models are compared with
experimental data from tests on tension rods as well as flexural
beams.In the light of the simple assumptions made and the random
nature of cracking, the accordance between the models and the test
data is quite good.Part II of the present thesis deals with
deformations in reinforced concrete disks subjected to pure
shear.A physical model for the shear stress-shear strain behaviour
of disks, including tension stiffening, is proposed.In the disk
model it is assumed that the tensile principal stress in the
concrete decreases linearly from the initiation of cracking until
a certain load level. At any load level the model can predict the
shear strains of the disk and the inclination of the crack system.
When regarding tension stiffening this latter parameter will be a
function of the load level.The model is compared with experimental
data, and in the light of the simple assumptions, quite good
accordance is found.Part III of the thesis deals with the
deformations of a beam symmetrically loaded by two concentrated
forces. In the shear-flexure beam model it is assumed that the
load is carried by means of a stringer system and a diagonal
stress field in the shear spans. In the shear spans the principal
tensile stress of the concrete is assumed to decrease linearly
from the initiation of cracking until a certain load level. The
deflections of the points of application of the loads is
determined, as is the inclination of the cracks. As was the case
in the disk model, this latter parameter will be a function of the
applied load.The model is compared with experimental data, and
surprisingly good accordance is obtained.

Original language | English |
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Number of pages | 133 |
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Publication status | Published - 1997 |

## Cite this

Christiansen, M. B., & Nielsen, M. P. (1997).

*Modelling Tension Stiffening in Reinforced Concrete Structures: - Rods, Beams and Disks*.