ROTATION CAPACITY OF REINFORCED CONCRETE BEAMS
by Metodi Andreev1
Summary
The plastic rotation capacity of a RC member is a decisive influence factor
for the redistribution of internal forces in statically indeterminate RC beams. The
value of the plastic rotation is dependent on many influence factors such as material
properties, cross section and system geometry.
In Eurocode 2 the allowable plastic rotation of a RC hinge is given only
depending on the ductility class of the steel and the neutral axis depth factor at
ultimate state xu d .Other influences like the concrete ultimate compressive strain,
type of steel (Phisical yielding steel PYS or Conditional yielding steel CYS), shape
of the bending moment diagram or the shear slenderness are not taken into account.
In this dissertation provides a detailed overview of the material models for
concrete and steel, methods for determining the length of the plastic hinges and
rotation capacity of RC beams.
In the theoretical part of the dissertation is developed a method of
determining the rotation capacity in the vicinity of selected plastic hinge in RC
beam with T and Г – shaped cross-section, as used the kinematic method for plastic
analysis. To determine the rotation span of the considered plastic hinge is used the
Langer’s model. Expressions are obtained for determining the rotation capacity
taking into account the bending for long ( q  6,0  7 ,0 ) and the bending and shear
for medium-length ( 2,0  2,5  q  6,0  7 ,0 ) beams. To account for the influence
of shear at D V  M areas in medium-length beam was developed model based on
the truss analogy. With the help of the developed computer program carried out a
number of numerical parametric tests by which was investigated the influence of:
- the type of concrete and steel as well as various parameters characterizing
their    diagrams;
- creep of concrete;
- compression reinforcement and its position along the height of the cross
section;
- shear forces.
Finally conclusions are drawn about the influence of the studied parameters
on the magnitude of the rotation capacity.
---------------------------------------------------------------------------------------------------Metodi Andreev , eng., Department of Reinforced Concrete Structures, UACEG, 1
Hristo Smirnenski Blvd., Sofia