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MATERIAL MATTERS Continued from page 15 integrates all aspects of SHM, including structural integrity monitoring, corrosion rate monitoring, and corrosion protection and prevention monitoring (e.g., CP monitoring), into one system. All hard- ware components (sensors, corrosion probes, anodes, reference electrodes, and \ZINÅK KWV\ZWT MY]QXUMV\ IZM QVKWZXW- rated into one centralized system; and monitoring and performance data are merged into one comprehensive report, accessible via the Internet through a Web-based user interface, that provides all essential information regarding the health of the structure. The intelligent [\Z]K\]ZM KWVKMX\ Q[ ]VQY]M +PMIQ\IVQ says, because it presents synchronized information about a structure—weather KWVLQ\QWV[ \ZINÅK TWILQVO KWZZW[QWV IK- tivity, corrosion protection functional- ity—that provides a complete picture for analyzing and understanding structural health. This concept was used to develop a SHM program for the Crusell Bridge, a landmark bridge in Helsinki, Finland that crosses the bay separating the western residential area of Jätkäsaari and the Ruoholahti district. The 25-m wide bridge, designed by WSP Finland and KWV[\Z]K\ML Ja ;SIV[SI WNÅKQITTa WXMVML in June 2011. It features two independent steel pylons that rise 49 m above sea level and two asymmetrical cable-stayed spans that total 143 m in length, with the lon- gest span measuring 92 m. The bridge's superstructure is constructed from longi- tudinally post-tensioned prestressed concrete beams and perpendicular beams that are a composite of steel and concrete. Cheaitani comments that the critical KWZZW[QWV ZQ[S QLMV\QÅML NWZ \PM +Z][MTT Bridge is corrosion of the superstruc- ture's reinforcing steel stemming from chlorides in road deicing salts. Although the structure spans the bay, the water is brackish with a low salt content and the durability assessment indicated a low risk of corrosion of the bridge piers. The complete substructure is coated to pro- tect the steel against corrosion. A CP system was not installed. The bridge's SHM program integrates a total of 92 different electrical, electro- KPMUQKIT IVL ÅJMZ WX\QK [MV[WZ[ _PQKP are installed in various locations on the bridge's deck, pylons, and expansion joint. "Structural intelligence was used in this exercise because placing sensors in the wrong location or putting the wrong sensor on the structure will give you in- formation that you don't need. It's not cost effective," Cheaitani says. The cor- rosion monitoring portion of the SHM program includes two corrosion measure- ment assemblies located at each end of the bridge deck that are comprised of a multi-depth, ladder-type corrosion rate sensor and seven corrosion potential sen- sors (reference electrodes) strategically placed in regards to the structure's geom- etry and exposure to factors that promote corrosion. The potential value of the steel rein- forcement bar in the concrete is measured by the electrochemical corrosion poten- tial sensors vs. manganese dioxide (MnO2 ) reference electrodes, and the corrosion rate is periodically measured using the galvanostatic pulse method. Data from the corrosion sensors are collected at se- lected intervals by a data management system, stored in a database, and synchro- nized with the other SHM data during analysis so that everything happening on the bridge can be viewed in real time on the Web-based user interface. Because the data are automatically coordinated and presented regularly, signs of corro- sion activity and structural deterioration can be detected promptly and provide early warnings of potential structural failure. Contact Atef Cheaitani, Savcor Group, Ltd.—e-mail: Atef.Cheaitani@savcor.com.au. Bibliography Cheaitani, A., and T. Laurila. "Latest Trends in Corrosion Control for New Reinforced Concrete Structures and a New Concept for Intelligent Structures." CORROSION 2012, paper no. C2012- 0001531. Houston, TX: NACE Interna- tional, 2012. 16 MATERIALS PERFORMANCE November 2012 NACE International, Vol. 51, No. 11