Civil Engineering Reference
In-Depth Information
Figure 6.36
Effect of 45
◦
and 0
◦
steel bars on pinching mechanism in cracked RC 2-D element (in
negative direction of a pure shear cycle)
In the reverse loading stage under negative shear stress from point B to point C (Figure
6.35b) both the vertical and horizontal cracks are open. The second drawing in Figure 6.36(b)
shows that the horizontal compressive stress
σ
H
is resisted by the compressive stress in the
horizontal steel bars, while the third drawing shows the vertical tensile stress
σ
V
to be resisted
by a tensile stress in the vertical bar. Both the compressive stress in the horizontal steel bar
and the tensile stress in the vertical steel bar contribute to the negative shear stress in the 45
◦
direction. As a result, the shear stress increases proportionally to the shear strain, and the large
shear stiffness in the BC segment in Figure 6.35(b) is sustained until the yielding of steel bars
at point C. The large stiffness of the BC segment and the horizontal CD segment creates a
fully rounded and robust hysteretic loop without the pinched shape.
Mohr circles
The smeared strains, the applied stresses, the smeared concrete stresses, and the smeared
steel stresses at the four points (A, B, C and D) chosen in Figure 6.35(a) and (b) have been
calculated by CSMM and are represented by Mohr circles for panels CA3 and CE3 (Mansour
