Page 559 - Forensic Structural Engineering Handbook

BUILDING FACADES 15.11

dimensions of typical wall components, displacements, crack widths, etc. Photographs and
detailed sketches of typical connections, anchors, and other relevant wall elements
observed at probe locations are helpful to document the as-built or existing configuration
of wall elements. These photographs and sketches are also used to confirm whether as-built
or existing conditions conform to the original construction documents.

Recording Procedures. Depending on the scope of the investigation, the volume of infor-
mation gathered can quickly become overwhelming. Organizing and cataloguing field notes,
photographs, samples, and any other information acquired is essential. Coordinated record-
ing procedures must be established and maintained throughout the investigation. Logical
and unambiguous nomenclature should be used to identify the date, time, and precise loca-
tion of conditions observed, and all other relevant information to avoid confusion and, in lit-
igation efforts, possible spoliation of evidence or interference with the chain of custody.

Sample Collection and Custody. Securing samples of visibly deteriorated or corroded ele-
ments and sometimes companion samples of undamaged elements is required for subsequent
laboratory testing. Since the opportunity to collect samples may be limited in the future, suf-
ficient samples should be taken during the close-up investigation. The quantity, locations, and
type of samples taken should be based on the nature of the failure and on the preliminary fail-
ure hypotheses developed. If the samples need to be statistically representative of the entire
subject wall or building, random samples may be required. Since purely random sample
selection is seldom possible due to limitations such as access restrictions or avoiding damage
associated with sample extraction, sample bias is almost always present. Sample bias should
be anticipated and fully understood so as to avoid inadvertently skewing the data.

Tools and Equipment. A wide variety of simple and more sophisticated investigation
tools is available to the facade investigator. The tools and equipments required to investi-
gate facade failures vary with the type of failure being investigated. However, certain tools
such as camera, flashlight, tape measure, binoculars, probe, hammer, knife, magnet, field
book, etc., are common to many investigations. Tools that are more sophisticated, provide
more accurate information, or are dedicated to a specific purpose may also be required.
Photographic equipment. A high-quality digital camera is a fundamental tool. A pro-
fessional photographer may be needed under certain conditions. A video camera may
be helpful if the conditions to be documented are rapidly changing.
Borescope. The fiberoptic borescope permits the investigator to view concealed spaces
such as wall cavities. The borescope’s small-diameter (6- or 8-mm) metal tube is
inserted through a small hole or joint. The device includes a power supply and light
source, as well as an eyepiece and camera mount (Fig. 15.6). In some cases a micro-
miniature camera can be used to capture digital still or video images.
Measuring devices. Simple measuring devices include a tape measure, plumb bob, and
optical crack comparator. More sophisticated devices such as a theodolite and electronic
distance-measuring (EDM) instrument are used to measure precise positions of visible
building facade areas relative to a reference point. High-precision global positioning
systems (GPS) and various inclinometors, accelerometers, and other devices can accu-
rately monitor building positions and movements. Computer-based laser distance mea-
suring equipment can be used to instantaneously measure wall surface positions and
profiles. Large quantities of data points can be integrated into CAD drawings to create
precise contour maps of the wall’s surface.
Moisture probe. Precise measurement and monitoring of moisture levels within walls
can be accomplished using humidity measuring systems developed for concrete. An