A recent restoration project on a 100-year-old, limestone-clad building provided an opportunity to evaluate the efficacy of certain non-destructive evaluation (NDE) techniques in identifying corrosion-related distress of embedded cramp anchors. After decades of service, progressive corrosion of the anchors had caused limestone delaminations and spalls, and presented a life-safety risk when fragments of limestone became dislodged and fell from the façade. Adding to this risk, it became clear early in the investigation that for certain areas of corrosion damage, stone cracking was not apparent on the surface or was otherwise difficult to detect. In an attempt to identify these pre-emergent cracks and delaminations, a range of NDE methods was considered to supplement the traditional techniques of visual identification and sounding. Of the NDE techniques implemented (i.e., ultrasonic pulse velocity surveys, infrared thermographic scans), infrared thermographic scans proved to be the more effective diagnostic tool to locate pre-emergent cracking and delamination sites, and showed promise as an early detection technique for similar buildings.
A recent restoration project on a 100-year-old, limestone-clad building provided an opportunity to evaluate the efficacy of certain non-destructive evaluation (NDE) techniques in identifying corrosion-related distress of embedded cramp anchors. After decades of service, progressive corrosion of the anchors had caused limestone delaminations and spalls, and presented a life-safety risk when fragments of limestone became dislodged and fell from the façade. Adding to this risk, it became clear early in the investigation that for certain areas of corrosion damage, stone cracking was not apparent on the surface or was otherwise difficult to detect. In an attempt to identify these pre-emergent cracks and delaminations, a range of NDE methods was considered to supplement the traditional techniques of visual identification and sounding. Of the NDE techniques implemented (i.e., ultrasonic pulse velocity surveys, infrared thermographic scans), infrared thermographic scans proved to be the more effective diagnostic tool to locate pre-emergent cracking and delamination sites, and showed promise as an early detection technique for similar buildings.
The occurrence of distortions within facade elements in the form of leaning, bowed and vertically displaced wall construction is common in older structures. Quite often these conditions are identified by building owners and serve as the primary focus of investigations to assess their significance. Quantifying the severity and extent of these displacements is integral to these evaluations. Various surveying methods are available to assist the investigator in determining planar distortions, ranging from simple plumb bob and level surveys to digital electronic surveying techniques. This paper focuses on the use of electronic surveying techniques as a diagnostic tool in assessing planar distortions and displacement in three dimensions on building facades. A case study is presented as a typical application where planar displacements within a building facade needed to be assessed. To provide context for selection, use, and interpretation of various survey techniques, a project is reviewed in detail from initial identification of displacements, review/selection of an appropriate survey technique, manipulation, and interpretation of survey data, assessing the significance of the data relative to the case study building, and review of repair program parameters.
The occurrence of distortions within facade elements in the form of leaning, bowed and vertically displaced wall construction is common in older structures. Quite often these conditions are identified by building owners and serve as the primary focus of investigations to assess their significance. Quantifying the severity and extent of these displacements is integral to these evaluations. Various surveying methods are available to assist the investigator in determining planar distortions, ranging from simple plumb bob and level surveys to digital electronic surveying techniques. This paper focuses on the use of electronic surveying techniques as a diagnostic tool in assessing planar distortions and displacement in three dimensions on building facades. A case study is presented as a typical application where planar displacements within a building facade needed to be assessed. To provide context for selection, use, and interpretation of various survey techniques, a project is reviewed in detail from initial identification of displacements, review/selection of an appropriate survey technique, manipulation, and interpretation of survey data, assessing the significance of the data relative to the case study building, and review of repair program parameters.
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