Nondestructive evaluation of prestressed concrete bridges using impulse response: Fid-Bau Portal

Nondestructive evaluation of prestressed concrete bridges using impulse response

Davis, A.G. / Petersen, C.G.

The Impulse Response nondestructive stress wave test method is presented for the evaluation of concrete conditions in pre-stressed and post-tensioned bridge units, such as pre-stressed hollow core beam bridge decks and post-tensioned box girders. The first case refers to pre-stressed concrete hollow core beam bridges decks, which are frequent on state highways in the USA. These bridges span between 15 and 35 m normally, with beam widths of 900 to 1200 mm. The beams are assembled with longitudinal grouted keyways and transverse cross bolts at 1/3 and 2/3 distance along the beams. Bridge deck performance can deteriorate over time because of loss of interaction at the grouted keyways, as well as corrosion of pre-stressing wires and cross bolts. The authors carried out a preliminary nondestructive testing survey on a 3-beam deck from an existing bridge, re-assembled in the University of Illinois Structural Laboratory. This study confirmed that the s'MASH Impulse Response NDT method could detect deterioration in the bridge system, and further tests were then performed in the field on an 11-beam bridge deck in the Chicago area. The test approach used and the results of the testing are discussed in this article. The second application concerns the evaluation of concrete quality in internally posttensioned box girders, either cast in place or pre-cast. In the case history presented here, s'MASH Impulse Response testing located deficiencies in the girder concrete such as poor compaction and delamination, as well as loss of post-tensioning caused by patching of partial exposures after post-tensioning and formwork stripping.