Analysis and modelling of the seismic behaviour of high ... - Ingegneria

4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS
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referred to as the elastic slope for the accelerogram. Calculation of the slope
for the rest of the accelerograms using the same procedure and calculation
of the median slope. The slope of this median line is referred to as the elastic
slope, Se.
c. Performance of a non-linear time history analysis of the structure
subjected to one of the accelerograms. Plotting of this point, called ∆1, on the
graph.
d. Increase of the amplitude of the accelerogram and repeat step c. This
may be done by multiplying the accelerogram by a constant, which increases
the spectral ordinates of the accelerogram by 0.1g. Plotting of this point as
∆2. Repetition of step 4 until the structure will be a mechanism or the
maximum rotation capacity of the components will be reached. When this
condition is reached, ∆i is the global drift capacity for this accelerogram.
e. Choice of another accelerogram and repetition of steps c through d
this for each accelerogram. The median capacity for global collapse is the
median value of the calculated set of drift limits.
The factors that affect the curve of the Incremental Dynamic Analysis (IDA)
are P-∆ effects, increment used for the analysis, ground motions used, strain
hardening ratio, shifting of fundamental period due to non-linearity, higher
mode effects, and shifting of maximum story drift location.
The accelerograms employed are characterized by strong motion duration of 10
sec with rise and decay periods of 2,5 and 5,0 secs respectively as shown Table
4.6. The generation of the spectrum compatible accelerograms was done
according to the method provided by Clough and Penzien (1993). At the end of the
generation process, in order to remove the drift in terms of displacement and
velocity in all the accelerograms, the method of the linear baseline correction
proposed by Meskouris (2000) was applied.
∆tr [sec] ∆tsm [sec] ∆td [sec]
2,5 10,0 5,0
Table 4.6. Rise, decay and strong motion durations
employed for the generation of the accelerograms
The generated spectrum compatible accelerograms were three and they were
referred to as A-03, A-12 and A-14. It is important to underline that the
accelerogram employed for the pseudo-dynamic tests on the prototype structure
was sorted out basing on the possible values and localization of the damage
induced into the structure at the collapse limit state. The selection of the
accelerogram was done considering the following parameters: