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3. GROUND SHAKING PREDICTIONS FOR HONG KONG
Based on results presented in Lam et al (2002) and Chandler et al (2002b), Table 3 1 summarises the
5% damped response spectrum predictions for design-level earthquakes affecting Hong Kong,
comprising critical very far-field events (R=280km) The results have been based on CAM model for
rock sites and FASA scaling model for soil sites
TABLE 3.1
RECOMMENDED PARAMETERS FOR SEISMIC RESPONSE SPECTRA FOR HONG KONG
Return
Period
(years)
PE
750
years
Rock 1
RSV max
(mm/s)
Rock 2
RSD mx
(mm)
S-Factor
for Soil
RSV raax
Soil 3
RSV^
(mm/s)
S-Factor
for Soil
RSDan
Soil 4
RSDo^
(mm)
70
500
1000
2500
50%
10%
5%
2%
34
70
84
100
12
25
30
36
65
57
55
54
220
400
460
540
29
26
24
24
35
64
73
86
1 for periods T falling between CAM bedrock response spectrum comer periods TI and ^T 2 (refer Fig. 1.1)
2 for periods T = 5 0 sec (Fig. 11)
3 for penods T falling between TI and site period T s , TI = corner period on Soil RSV response spectrum (Fig 2 2)
4 results correspond to period T = site period T s , values quoted are for T s = 1.0 sec and can be scaled in proportion to T 5>
provided T s < X m T 2 : X m = 1 - (M-5)/6 [Lam and Chandler (2002)]
4. DRIFT PREDICTIONS FOR HONG KONG BUILDINGS
In the recently established displacement-based approaches for seismic assessment of buildings, for
example Priestley (1995), the overall drift demand at effective height of building (or at roof level) is
compared with the corresponding drift capacity curve in order to assess the degree of damage as well
as the factor of safety of the building This approach cannot however distinguish whether the drift is
uniformly distributed at each storey or is concentrated at a particular storey that may be caused, for
example, by the presence of a soft storey or by higher mode effects It is important to recognize that
local deformation associated with high inter-storey drift would cause significant damage to the nonstructural
(NS) components and high internal forces to develop in particular structural elements such as
columns and coupling beams In this section, which starts with the estimation of overall lateral seismic
drift demand, a prediction formula for maximum inter-storey drift demand of buildings with due
consideration of higher mode effects and potential soft storey effects will be presented.
The average building drift angle # a v g defined as the ratio between the roof seismic displacement and the
height of building can be estimated by the equation [Chandler et al (2002b)]
=165 RSD l
(41)
The maximum seismic inter-storey drift angle #max (due to the combined seismic vibration modes) can
be related to the effective first-mode displacement RSD\ using the following generic expression: