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responded in a fairly similar manner, confirming the effectiveness of the criteria developed for
generating the structures. The maximum top displacement of the structures, within the same group,
shows a slight increase as the concrete strength increases. This is consistent with the load-displacement
curves generated under static loading. The higher strength concrete experiences slightly more
softening beyond a certain strain, in the initial ascending branch of the curve. This is partially
attributable to the cracking of the concrete cover. In all instances, the maximum top displacement of
the structures in the R and RS groups are greater than those structures of the same concrete strengths in
the E group.
N80R N100R N120R
FIGURE 4
SAMPLE PLASTIC HINGE LOCATIONS
(SHADED AREAS ARE PLASTIC HINGING IN THE WALL)
The plastic hinges formed in the different structures show that the number of column hinges generally
increases with increasing concrete strength. This is attributable to the higher strain levels in the steel,
due to the increase in strength and modulus of elasticity of the concrete. Although the strong-column
weak-beam provision of the code was satisfied in the design, the 120 MPa concrete structures in the R
group show substantially more hinging in the columns, as shown in Figure 4. The use of high yield
steel in the beams and normal grade steel in the columns of the R structures has an adverse effect in
terms of increased number of column hinges. The RS group, which used high yield steel in the
columns, had fewer column hinges, even at high levels of loading. On the other hand, the spread of
inelasticity in the shear wall is unaffected by the change in concrete strength. The use of normal grade
steel with high strength concrete does not cause undesirable consequences in the wall. For the beams,
at twice the design PGA, yielding has occurred in almost all cases. This is both expected and desirable
at this level of loading.
To study local effects, the curvature ductility demand of a number of beams at different locations in
the structure, was calculated. The maximum curvature ductility demand in the beams is shown in
Table 6.