Principal Investigator(s) and
Institution(s)
Mehmet Çelebi, U.S. Geological Survey
Nicholas P. Jones, Consultant
Objective
The acquisition of structural response data during earthquakes is essential to confirm and
develop methodologies for analysis, design, repair and retrofitting of earthquake
resistant structural systems. Particularly for urban environments in seismically active
regions, acquisition of response data from structures including lifelines such as bridges,
by using seismic instrumentation, is one of the basic requirements for a thorough
investigation of the effects of earthquakes on the structures. In order to understand the
structural responses thoroughly, it is necessary to record ground motions at the
free-field in the vicinity of the structures, in addition to structural arrays which
should include sensors for soil-structure interaction (SSI) effects. The New Madrid area,
the location of the 1811 - 1812 New Madrid earthquakes, is a seismically active region
requiring earthquake hazard mitigation programs including those related to investigation
of strong shaking of structures and the potential for ground failures in the vicinity of
structures.
The objective of this task is to develop a detailed and executable scheme for seismic
instrumentation of the Cape Girardeau cable-stayed bridge across the Mississippi River
between Missouri and Illinois, which is currently under construction. The instrumentation
will be deployed on and in the vicinity of the new bridge.
Approach
Early planning of seismic instrumentation schemes is a necessity in order to cover
installation of basic hardware during the construction phases (such as conduits and cables
to interconnect the sensors to recorders and conduits for deployment of downhole
accelerometers). In addition to other objectives which may require special purpose
instruments and hardware, for seismic engineering studies, three other objectives are
sought. In planning for the overall scheme, it is important to clearly identify these
objectives:
1. Instrumentation of the superstructure and pier foundations.
2. Instrumentation of the free-field in the vicinity of the structure including those
related to downhole measurements and horizontal spatial arrays to assess the differential
motions at the piers of the long span structure.
3. Ground failure arrays in the vicinity of the structure.
The scope of this task is limited to detailing the seismic instrumentation covering the
first two objectives only. In developing the instrumentation scheme, geotechnical
considerations related to the bridge will be taken into account. It is important to note
also that the proposed instrumentation is for strong-motion recording and not for
low-amplitude weak motions. For low-amplitude weak motions, which are outside the scope of
this task, special purpose temporary deployment schemes should be adopted.
The actual acquisition of hardware for instrumentation will be done via funding allocated
under related project Task F2-2.
Through this task, the USGS will:
Prepare the instrumentation design (scheme and detailed plans for implementation). In
carrying out this subtask, only state-of-the-art hardware will be considered;
Develop the itemized list of hardware;
Solicit vendor quotations in accordance with purchase procedures set by the FHWA project
contract officer and MCEER project manager; and provide technical consulting support to
the Missouri Department of Transportation (MoDOT) during the installation of the system.
It is assumed that MoDOT will be responsible for the actual hardware
installation/construction.
USGS, as part of its earthquake hazard reduction program, in addition to carrying out the
above tasks in designing and deployment of instrumentation, will also establish a
mechanism and appropriate agreements with MoDOT and the FHWA to maintain the instruments,
retrieve, process, and disseminate strong-motion response data following events in the
future.
In addition, a consultant (Dr. Jones) will be employed to conduct an independent review
and check of the final instrumentation design prepared under item 1 above.
Anticipated Start Date and Duration
January 1, 1999 - 24 months
9/24/99 |