Bending Element Definition
Elements that are under the effect of a simple bending moment around any of their principal axes. In the elements under the effect of simple bending, the loads should act in the plane parallel to the principal axis passing through the shear center or the element should be supported against torsion at the load impact points and supports.
Flow Limit State
It is a situation where the cross section of the beam is dimensioned to remain stable until it becomes plastic under the effect of bending, if the local buckling of the pressure head and the lateral twisting buckling is prevented. In this case, the characteristic moment strength can be taken equal to the plastic moment strength.
The yield moment is the moment value when the uppermost fiber of the section under the influence of bending moment reaches the yield stress.
Plastic Moment is the moment value when all fibers of the section under the effect of bending moment reach the yield stress.
Lateral Torsional Buckling Limit State
The part of the beam in the pressure head area acts like an axially loaded pressure bar. If the stability of the pressure head is not sufficient, the beam section cannot reach its full bending capacity. In this case, similar to the pressure elements; General buckling or loss of stability in cross-sectional parts that may occur with local buckling determines the collapse limit state. This type of buckling of the pressure head is called lateral torsion buckling.
Design with ÇYTHYE 2018
9.2.1 - Flow Limit State
The characteristic bending moment strength M n for the yield limit state is calculated by equation 9.2.
9.2.2 Lateral Torsional Buckling Limit State
For the lateral torsion buckling limit state, the characteristic bending moment strength for 3 different failure limit conditions, the laterally unsupported length of the pressure head M n , the change due to L b and the effect of the moment correction coefficient C b are shown in the figure below.
a) If L b ≤ L p , this limit situation need not be taken into account.
b) If L p <L b ≤ L r , the characteristic bending moment strength M n is calculated by equation 9.3.
c) If L b > L r , the characteristic bending moment strength M n shall be determined by equation 9.4.
C b Coefficient: It is the positive contribution of bending moment propagation along the length between the points supported by the lateral stability connection in the case of lateral torsional buckling limit.
Design Under Combined Effect
It is the strength calculation made by taking into account the combined stresses created in the elements under bending and axial force.
Account details are available at Birleşik Etki Altında Tasarım .
Icons
C b : Moment correction coefficient defined by Equation 9.1
E: Structural steel modulus of elasticity
F y : Structural steel characteristic yield stress
I ts : Effective radius of inertia
J: Torsion constant
h o : Distance between center of gravity of cross section heads (= d -tf)
L b : Element length between the points where lateral displacement and cross-section twisting in the pressure head are prevented
L p : Laterally unsupported boundary length for the flow limit state
L r : Limit length in non-elastic lateral twist sprain
M n : Characteristic bending moment strength
M p : Plastic bending moment
W px : plastic strength moment about the x-axis
W ex : moment of elastic strength around the x-axis