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原文传递 EVALUATION OF ROCKY POINT VIADUCT CONCRETE BEAM.

题名：	EVALUATION OF ROCKY POINT VIADUCT CONCRETE BEAM.
作者：	Cramer-SD; Covino-BS Jr.; Holcomb-GR; Bullard-SJ; Russell-JH; Dahlin-CM; Summers-CA; Laylor-HM; Soltesz-SM
关键词：	Cathodic-protection; Chloride-content; Chloride-migration; Coastal-engineering; Concrete-; Concrete-cover-depth; Construction-management; Corrosion-; Design-; Deterioration-by-environmental-action; High-performance-concrete; Oregon-; Properties-of-materials; Reinforced-concrete-bridges; Reinforcing-bars; Service-life; Silica-fume; Stainless-steel; Viaducts-
摘要：	This study was intended to determine why it was necessary to replace the Rocky Point Viaduct (1954-1994), on the Oregon coast south of Port Orford, after a period of service that was much shorter than that of many other reinforced concrete bridges on the Oregon coast; to identify construction practices that may have contributed to its early failure; and to identify evaluation methods that are most effective for characterizing bridge condition. A 14.3 m (47 ft) section of concrete Beam A1 and bridge deck between the north abutment and pier 1 was removed from the seaward side of the Viaduct for evaluation of: (1) concrete properties; (2) reinforcing bar (rebar) corrosion; and (3) chloride migration in the concrete. The harsh environment at the site was an important factor in the premature failure of the Viaduct. This led to substantial salt penetration of the concrete to the depth of the shear stirrups and square rebar. The severity of chloride penetration of the concrete was such that neither the original concrete cover nor subsequent efforts to repair the structure and prevent further corrosion could mitigate its effects on rebar corrosion. Shear stirrups had inadequate concrete cover for the severity of the environment. Early corrosion damage could be predicted from chloride depth profiles, concrete cover depths, and the rebar corrosion threshold. Application of the patch concrete merely delayed, but not for long, the occurrence of highly corrosive conditions around shear stirrups and the square rebar. Other efforts at preventing further corrosion damage were ineffective. Chloride profiling, using concrete powder samples taken at small depth increments, is one of the most powerful techniques the Oregon Department of Transportation (DOT) has for assessing the condition of bridges on the Oregon coast. The other is half-cell potential mapping. Impressed Current Cathodic Protection (ICCP) over a period equivalent to 15 years service at Oregon coastal bridge conditions resulted in significant extraction of chloride from around the outer rebar. Bridge construction practices should consider, in addition to quality concrete and adequate cover, the aggressiveness of the site environment, including meteorological conditions and washing and sheltering that affect chloride deposition. Assessment of site environmental conditions would be useful to bridge design to assure a structure would achieve the desired service life. Site environments could be characterized by one of the following: measurement of atmospheric corrosion rates for mild steel; measurement of salt deposition rates; or chloride profiling an existing or nearby structure. Chloride profiles for coastal bridges and a knowledge of corrosig600
总页数：	2000/06. pp162 (Phots., Figs., Tabs., Refs., 6 App.)
报告类型：	科技报告