TBDY Section 5.4.2. Modeling Beams and Columns - Beams and columns shall be modeled as frame (bar) finite elements . Nonlinear behavior is defined in the end element finite plastic deformation zones ' in 5.3.1 according stacked plastic behavior with a model or 5.3.2 according to the spread plastic behavior can be modeled by models. The use of the stacked plastic hinge model can generally be considered sufficient in practice. - All six degrees of freedom shall be taken into account at the joints of columns and beams. If slabs are modeled as rigid diaphragms, those that correspond to rigid movement of these degrees of freedom will be removed. - In columns and beams, plastic hinges may be placed just outside the column-beam junction, in other words at the ends of the clear span of columns or beams. However, it should be taken into account that plastic hinges may also occur in beam openings due to the effect of vertical loads. - Reinforced concrete columns and beams shall be modeled as linear elements along the length between the plastic joints at the ends . The effective section stiffness of these elements will be determined according to 5.4.5 .