The Design of Modern Steel Bridges - TEDI

120 The Design of Modern Steel Bridges
Figure 5.13 Tension field due to shear stress.
Figure 5.14 Post-buckling behaviour under bending stress
in the boundary members due to the pulling-in forces in the plate. In the
post-buckling stage, the stiffness of the plate against shearing deformation
ranges from 0.75 to 0.90 times the shear modulus G, depending upon the
flexural stiffness of the boundary members. In a vertically stiffened web plate
of a girder, the pulling-in forces on the two sides of intermediate vertical
stiffeners balance, leaving only vertical compression to be resisted by them.
But the flexural stiffness of the flanges has a significant influence on the
magnitude and pattern of the tension field.
A plate subjected to pure bending stresses also has significant post-buckling
capacity. As the applied stresses reach the elastic critical value, buckles appear
in the compressive part of the plate. With further increase in loading, the
distribution of the bending stresses changes, with no further compressive stress
in the buckled portion, but the rest of the plate continues to resist the increase
in loading, as shown in Fig. 5.14.