Mehmet Celebi
2008
<div class="NLM_paragraph">Earlier papers have described how observed data from classical accelerometers deployed in structures or from differential<span> </span>GPS<span> </span>with high sampling ratios deployed at roofs of tall buildings can be configured to establish<span> </span>seismic<span> </span>health monitoring of structures. In these configurations, drift ratios<sup>1</sup><span> </span>are the main parametric indicator of damage condition of a structure or component of a structure.</div><div class="NLM_paragraph"><br data-mce-bogus="1"></div><div class="NLM_paragraph">Real‐time<span> </span>measurement<span> </span>of displacements are acquired either by double integration of accelerometer time‐series data, or by directly using<span> </span>GPS.<span> </span>Recorded sensor data is then related to the performance level of a building. Performance‐based design method stipulates that for a building the amplitude of relative displacement of the roof of a building (with respect to its base) indicates its performance.</div><div class="NLM_paragraph"><br data-mce-bogus="1"></div><div class="NLM_paragraph">Usually, drift ratio is computed using relative displacement between two consecutive floors. When accelerometers are used, a specific<span> </span>software<span> </span>is used to compute displacements and drift ratios in realtime by double integration of accelerometer data from several floors. However, GPS‐measured relative displacements are limited to being acquired only at the roof with respect to its reference base. Thus, computed drift ratio is the average drift ratio for the whole building. Until recently, the validity of<span> </span>measurements<span> </span>using<span> </span>GPS<span> </span>was limited to long‐period structures<span> </span><span class="equationTd inline-formula"><span id="MathJax-Element-1-Frame" class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML" overflow="scroll" altimg="eq-00001.gif"><mi>(</mi><mi mathvariant="normal">T</mi><mtext>&gt;1&#x2009;</mtext><mi mathvariant="normal">s</mi><mi>)</mi></math>"><span id="MathJax-Span-1" class="math"><span><span id="MathJax-Span-2" class="mrow"><span id="MathJax-Span-3" class="mi">(</span><span id="MathJax-Span-4" class="mi">T</span><span id="MathJax-Span-5" class="mtext">>1 </span><span id="MathJax-Span-6" class="mi">s</span><span id="MathJax-Span-7" class="mi">)</span></span></span></span></span></span><span> </span>because<span> </span>GPS<span> </span>systems readily available were limited to 10–20 samples per seconds (sps) capability. However, presently, up to 50 sps differential<span> </span>GPS<span> </span>systems are available on the market and have been successfully used to monitor drift ratios [1,2]—thus enabling future usefulness of<span> </span>GPS<span> </span>to all types of structures. Several levels of threshold drift ratios can be postulated in order to make decisions for inspections and/or occupancy.</div><div class="NLM_paragraph"><br data-mce-bogus="1"></div><div class="NLM_paragraph">Experience with data acquired from both accelerometers and<span> </span>GPS<span> </span>deployments indicates that they are reliable and provide pragmatic alternatives to alert the owners and other authorized parties to make informed decisions and select choices for pre‐defined actions following significant events.</div>
application/pdf
10.1063/1.2963922
en
American Institute of Physics
Seismic monitoring to assess performance of structures In near‐real time: Recent progress
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