Deformation Problems in Reinforced Concrete

Research on deformation problems in reinforced concrete in Denmark has been scanty, due to the relatively high focus on strength problems during decades. In this project some important deformation problems are studied. The purpose is to model reinforced concrete in much the same way as the load carrying capacity problems have been modelled.
In uniaxial problems the crack formation model developed by David Holkmann Olsen is refined to make it possible to take into account tension stiffening effects. The uniaxial model then is extended to bending in beams.
In shear problems the diagonal compression field is used and in the linear-elastic cracked state the governing parameters are determined by minimization of the complementary elastic energy. Besides beams in bending and shear, disks in pure shear will be treated.
The results of these efforts has been partly published, see Publications.
Later is it attempted to use the same model for combined actions in beams, first of all combined bending and torsion, in which case the stiffness properties are important in lateral stability problems.
In a following phase stress calculation for complex stress states is dealt with. Focus will be on stresses in reinforcement near concentrated forces, a problem which arises in connection with anchorage of prestressing reinforcement. As a biproduct modelling of crack tip stress fields near sharp cracks are studied by using the same stress fields. This part of the project has been published, see Publications, Morten Bo Christiansen.
Finally, stress and stiffness determination is carried out in box girders by means of the models investigated. The importance of warping stresses and warping deformations are studied. The theory is thought to combine ideas of the Vlasov theory for thin-walled closed sections and ideas developed in the first phases of the project.