Civil Engineering Reference
In-Depth Information
Smooth cyclic demand spectra have been formulated by Malhotra (2002) by using the cumulative
damage model for low-cycle fatigue of Coffi n (1954) and Manson (1954). The results of the extensive
parametric study showed that the number of cycles, and hence the cyclic demand, decreases as the
damping ratios increase. Damping ratios
ΞΎ
affect the cyclic demand spectra only for systems that are
of intermediate stiffness.
3.7 Use of Earthquake Databases
Contrary to the situation in the 1970s and earlier, high- quality strong - motion data are freely available.
Some sources of strong-motion data on the web are as follows:
(i) http://db.cosmos - eq.org : The web site of the Consortium of Organisations for Strong - Motion
Observation Systems (COSMOS) allows access to a relational database of strong ground- motion
parameters. Data are provided by the core members, i.e. US Geological Survey, California
Geological Survey, US Army Corps of Engineers and US Bureau of Reclamation, for several
earthquake - prone regions worldwide.
(ii) http://www.consrv.ca.gov/cgs/smip/ : The California Strong - Motion Instrumentation Program
(CSMIP) records the strong shaking, both free fi eld and in structures during earthquakes for
engineering use through a state-wide network of strong- motion instruments.
(iii) http://peer.berkeley.edu/smcat/ : The Pacifi c Earthquake Engineering Research Center (PEER)
database contains records of earthquakes publicly available from Federal, State, and private
providers of strong-motion data. The database includes earthquake strong motions from several
active regions worldwide.
(iv) http://www.isesd.cv.ic.ac.uk/esd : In this European Commission project site, acceleration time
histories are archived as uncorrected and corrected records, together with the corresponding
elastic response spectra. The acceleration time histories are from earthquakes in Europe and
adjacent areas.
(v)
http://www.k - net.bosai.go.jp : Kyoshin Net (K -NET) is a Japanese government project network,
which avails of strong-motion data on the Internet. Such data are obtained from observatories
deployed all over Japan.
There are many other sites, but the above provide a reasonable representation of the data freely
available for downloading. Such records, if presented in their raw format, require baseline correction
and fi ltering. Software for strong-motion processing is also abundant and is discussed below. Some of
the above-mentioned earthquake databases provide response spectra online. For example, the PEER
strong-motion site provides two types of search: earthquake or station characteristics and peak values
can be selected or parameters for the response spectra specifi ed as displayed in Figure 3.22 . Moreover,
earthquakes are archived on the basis of (i) source mechanism and distance, (ii) location and station,
(iii) site classifi cation, (iv) component, (v) date and time, and (vi) magnitude. Characteristics of low-
and high- pass fi lters are also specifi ed.
The results of the search for the 1995 Kobe earthquake are provided in Figure 3.23 . Three compo-
nents, i.e. two horizontal and one vertical, are available at 12 stations as shown in Figure 3.23 . The
source data were provided by the Conference on the Usage of Earthquakes (CUE), Railway Technical
Research Institute of Tokyo. The characteristics of high- pass and low - pass fi lters are included. Peak
ground values of acceleration (PGA), velocity (PGV) and displacement (PGD) are also provided. The
acceleration, velocity and displacement time histories for the Kakogawa vertical component are pro-
vided in Figure 3.24, along with the 5% damping response spectra.
The ASCII fi les are also available for each earthquake components; thus, the strong motions can be
used as input for structural assessment. Response spectra are also available in ASCII format for differ-
ent values of damping.
