A summary of existing knowledge and practice on various nondestructive and near nondestructive methods for evaluating the cross-sectional loss of prestressing steel strands embedded in concrete bridges was completed as Phase I of the project and published as NCHRP Web Document 23
. A Phase II was designed to develop or modify promising techniques; however, no such techniques emerged and the contract was concluded on the completion of Phase I.
Prestressed concrete bridges are relatively new compared with reinforced concrete and steel bridges, and, generally, their performance has been good. However, incidents of deterioration and failure have been reported in various countries. Concerns for the condition and safety of prestressed concrete bridges in the United States arise from these failures and some observed deterioration. Determination of load-carrying capacity is possible only with a reliable evaluation of the integrity of the prestressing steel in concrete bridges. No economical field method exists for determining the condition of prestressing steel. Considerable research to address this problem has been performed over the past 15 years but has yielded limited practical results. New technologies or modifications of previously investigated technologies were needed for developing reliable, cost-effective field methods for evaluating the condition of prestressing steel in bridges.
The objective of this research was to develop and demonstrate method(s) for evaluating the condition of prestressing steel in pretensioned and post-tensioned concrete in-service bridge superstructures to determine load-carrying capacity.
Research was intended to identify one or more field methods to detect and measure loss in cross-sectional area of prestressing steel due to corrosion or fracture. Under Phase I of the project, the research team reviewed and summarized existing knowledge and practice. Based on the findings of Phase I, recommendations were to be made for modifying existing methods or developing new methods. The project concluded after the completion of Phase I. As anticipated, no technologies, new or existing at the time, appeared advanced enough to invest the minimal resources available to the NCHRP into this project. The Phase I report that summarizes the technologies examined has been published in portable document format (PDF) as NCHRP Web Document 23
. (A free copy of Adobe Acrobat Reader is available at https://www.adobe.com