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TABLE 6
MAXIMUM CURVATURE DUCTILITY DEMAND IN BEAMS
Model
EC8-1
EC8-2
EC8-3
0.4g
3 11
373
2.33
E- group
0.8g
7 15
703
6.09
0.4g
1 68
1.63
165
R - group
0.8g
399
383
3.05
RS - group
0.4g
1 71
1 68
167
0.8g
3.87
3.90
3.12
It is interesting to note that the maximum curvature ductility demand, given in Table 7, occurred in the
normal strength concrete structure and the equivalent stiffness HSC structures. The ductility demand at
a PGA of O.Sg is already on the high side, but is within achievable ductility capacity of well-detailed
members. For the R and RS structures, the ductility demand is significantly less compared to those of
E group. Since the R and RS group structures use high yield steel in the beams, the strain that defined
yield is much higher compared to normal strength steel; hence, a higher yield curvature and
consequently, a lower ductility demand was observed.
TABLE
CALCULATED COLLAPSE PGA, YIELD PGA AND RESPONSE MODIFICATION
Model
N35
N80
N100
N120
N80R
N1GOR
N120R
N80RS
NIOORS
N120RS
EC8-1
0.841
0.870
0.868
0.893
0.934
0.958
0.984
0.963
0.959
0.997
Mg)
EC8-2
0.950
0.982
0.954
0.970
0.864
0.911
0.939
0.901
0.918
0.958
EC8-3
0.902
0.871
0.847
0.869
0.980
0.898
0.876
0.980
0.869
0.853
EC8-1
0.150
0.107
0.106
0.105
0.100
0.111
0.117
0.101
0.114
0.121
Me)
EC8-2
0.150
0.107
0.106
0.105
0.100
0.111
0.117
0.101
0.114
0.121
EC8-3
0.150
0.107
0.106
0.105
0.100
0.111
0.117
0.101
0.114
0.121
EC8-1
5.61
8.13
8.19
8.50
9.34
8.63
8.41
9.53
8.41
8.24
Rorq
EC8-2
6.33
918
900
9.24
8.64
8.21
8.03
8.92
8,05
7.92
EC8-3
6.01
8.14
7.99
8.28
9.80
8.09
7.49
9.70
7.62
7.05
For simplicity, the response modification factor (R in US practice and q in European practice) is
defined as the ratio of the ground acceleration of the earthquake that caused the attainment of the
ultimate limit state, to that of the earthquake corresponding to the yield limit state. Of all the structures
considered, the normal strength structure has the lowest response modification factor. This is
attributable to it having a much larger level of overstrength, compared to the other structures. The extra
steel reinforcement, provided for gravity loading in the normal strength concrete, has affected its
energy dissipation capacity in the inelastic range. The behaviour factor for structures in the E group is
almost constant. On the other hand, the behaviour factor generally decreases with increasing concrete
strength for both the R and RS structures (with very few exceptions). Comparison of the calculated
behaviour factors suggest that, in terms of structural ability to respond in the inelastic range, the 80
MPa concrete is the most effective for the given structural configuration.