No abstract

No abstract

No abstract

No abstract

Ground Penetration Radar (GPR) as a non-destructive (NDT)-method can be applied to obtain detailed information about the inner structure and condition of bridges without damaging the structure. In this paper the capabilities and limitations of the application of the fast inspection technique GPR will be demonstrated. In addition to GPR investigations, geoelectrical measurements, coring and petrophysical investigations have been carried out. The investigated railway bridge in Oleśnica is a typical European masonry arch bridge (age, construction and span length). It shows typical damage to the masonry arches such as increasing salt concentration, destruction, material losses and longitudinal cracks. Radar measurements were carried out with two main objectives: (1) Identification of basic geometric dimensions of the bridge and identification of construction details; (2) Evaluation of the condition of the masonry, such as mechanical damage (e.g. cracks) or variation of the moisture content. Radar antennas of different frequencies (having different penetration depths) have been used to estimate the thickness of the walls. Because of the high attenuation in the inner masonry structure the measurements have not produced satisfying results, but the radar measurements have been successfully applied to investigate the moisture distribution in the masonry. These results have been verified by coring and through geoelectrical measurements. Cracks were studied at two testing areas at one wing wall of the bridge using an automatic 2D radar scanning system. The radar data were processed using advanced data processing tools like FT-SAFT reconstruction and data fusion. The processing sequence allowed the creation of high-resolution depth sections (C-Scans).

No abstract

No abstract

roded reinforcing mesh. In indoor slabs, delamination typically appears as a single, shallow, horizontal, near-surface separation oriented parallel to the finished surface. Delamination may affect areas as small as a few square inches to more than 100 ft 2 and occurs at a depth ranging from very shallow [ 1 ⁄16 in. or (1.6 mm)] to 3 ⁄4 in. (20 mm) or deeper in the outdoor slabs (2, 3).Jana (2) has summarized the common causes of delamination as (a) the use of air entrainment in a concrete slab receiving a handtrowel finish; (b) machine-trowel finishing a lightweight aggregate concrete slab; (c) premature finishing of a slab before the cessation of bleeding; (d) top-down stiffening or surface crusting of a concrete slab under hot, windy, or dry weather conditions, especially if the slab is undergoing slow and prolonged bleeding; (e) prolonged finishing operations on an outdoor air-entrained concrete slab or on a slab receiving a mineral or metallic surface hardener; ( f ) corrosion of reinforcing steel in concrete due to chloride ingress or carbonation; and (g) cyclic freezing and thawing of a poorly or non-air-entrained concrete slab at critically saturated conditions.No matter what the underlying cause, delamination is a nuisance in in-service concrete slabs. Delaminations grow over time and may eventually develop into large planes of separation that result in surface peeling and spalling. In concrete bridge decks, delamination is regarded as an indirect indication of severe steel rebar corrosion, and thus the extent of delamination measures the severity of deck deterioration. To take timely preventive measures and to avoid the high cost of bridge deck demolition and reconstruction, early detection of delaminations is necessary. Bridge owners and highway agencies have long been conducting so-called traditional deck surveys including visual ones, electromechanical sounding, hammer sounding (i.e., metal tapping), and chain drag (ASTM D4580-03) for routine inspection and identification of delaminated zones in bridge decks (and rigid pavements). More sophisticated nondestructive testing (NDT) techniques such as ground-penetrating radar and impact echo (IE) have been recently adopted by some transportation agencies (4). Among other NDT techniques, activepassive infrared thermography has demonstrated great potential for detection of shallow delaminations (ASTM D4788-03). Implementing such advanced techniques offers several advantages over the common practice of traditional surveys, including reducing the number of necessary cores and the cost associated with the coring operation, obtaining a more objective condition assessment, detecting deterioration at its early stages of development, and full coverage of the test deck with minimal or no traffic interruption. The ultimate anticipated value-added is a reduction in the overall life-cycle costs.