3.2 QA/QC of New Deckds

QA/QC of New Decks...

Quality Control (QC) is the implementation, measurement, and enforcement of sound construction practices and jobsite inspections to ensure construction quality. Quality Assurance (QA) is the inspection and testing of the completed product, in accordance with specifications intended to verify the quality of the completed structure.

Table 1. Bridge deck monitoring.

Vibratory Motion	Frequency Range	Sensor Type (with link to example)	Motion Measured	Application (with link to example)
Tilt, or Rotations	0-1Hz	Tiltmeter http://www.geomechanics.com/products/tiltmeters.htm Inclinometer http://www.slopeindicator.com/instruments/inclin-intro.html	Rotation from vertical in degrees, sometimes expressed as the sine of the angle of tilt	Monitoring long term movement of bridge decks http://www.bridgetest.com/
Motion due to earthquakes	0-200Hz	Accelerographs http://www.kinemetrics.com/etna.html http://www.kinemetrics.com/qdr.html Structural monitoring system http://www.kinemetrics.com/ oasis.html	Absolute acceleration, m/sec²	Monitor the performance of individual structures during earthquakes, such as piers, decks, and foundations http://www.kinemetrics.com /amoes.html Monitoring the performance of large structural systems http://www.kinemetrics.com/ structural.html http://www.kinemetrics.com/ namhae.html http://www.kinemetrics.com/ halkis.html
Strains due to motions	0-100Hz	Strain gages Bonded http://www.vishay.com/brands/ measurements_group/strain_gages/ mm.htm http://www.geokon.com/straingages. htm http://www.jptechnologies.com/ wsgages.html http://pages.prodigy.net/heatinc/ http://www.bridgetest.com/	Strain, mm/mm or in/in	Monitoring stresses in structural elements at critical location, steel and concrete Evaluate fatigue in structural elements
Motion due to ambient vibration to evaluate structural characteristics	1-100Hz	Vibration Monitoring http://www.kinemetrics.com/k2.html	Acceleration, m/sec² sometimes velocity, m/sec	Measure modal characteristics to "calibrate" the designers mathematical model ftp://ftp.kmi.com/pub/AppNotes/ appnote44.pdf

QC programs intended to address construction quality of decks routinely include (a) visually inspecting the forms and deck reinforcement at regular intervals during construction (and carefully repairing nicks and scratches found in epoxy-coated bars within the reinforcing cage with fresh epoxy); (b) careful field and laboratory testing of the quality of materials used in its construction; and (c) testing and inspection activities, both in the field and laboratory, associated with placing and curing the concrete. Results are carefully measured and archived as a permanent part of the job record and/or used to modify field (construction and inspection) practices and take corrective action while construction is still underway.

Quality control of construction practices and materials selection contributes to a deck that can last at least as long as its design life, from meticulous construction and inspection of the reinforcing cage to care in designing, mixing, placing, finishing and curing the concrete, along with proper monitoring during each of these processes. This quality-control series of activities is consistently practiced, in general, throughout most of the industry.

However, the quality assurance component, particularly as it relates to inspection of the internal condition of the deck after construction, generally receives much less attention and care, because it seems to be physically more difficult to do. In addition, when accuracy or reliability of QA inspections come into doubt, QA can often be viewed as an added construction cost with low, or indeterminate, perceived value. Well-written QA verification specifications in terms of the desired inspection outcomes and consequences related to noncompliance often become seemingly meaningless when inspection capabilities appear to fall short of expected results. This statement is particularly true when the inspection methods cannot be effectively critiqued or corrected, resulting in an inherent ineffectiveness in their ability to be used for enforcement or improvement of QA policies.

Ultimately, it is not how well a deck appears to have adhered to standard practice prior to completion that matters in the end. More importantly, the design elements intended to be built into the structure must actually exist internally once it is finished. In other words, excellent QC is not much good without adequate QA. The only way to ensure compliance to construction requirements is to construct and adopt a meaningful, high-quality QA program that undeniably verifies the deck has been properly built. This includes development and implementation of good specifications, backed by selection of appropriate inspection methods that are accurate and repeatable for verifying compliance, to inspire confidence in both the construction community and the owners that the QA program is sound.

QA Using Geophysical Methods