João Carlos Souza has a primer up on ArchiNet on how to identify problems in concrete buildings based on crack patterns. Putting aside some bad translation from Portuguese to English* it’s quite good and can help identify damage when used as intended.
Mr. Souza does not explicitly state the assumptions that went into his visual glossary of cracking, but they can be seen in is diagrams: he’s talking about modern** buildings with two-way slabs*** and spandrel beams. If the building has columns reinforced in non-standard ways as was permitted by code in as late as the 1920s, or has low-strength concrete as was common through the 1940s, or has one of the strange patented rebar systems that were in use through the 1910s, this guide may be inaccurate.
Those problems don’t mean that the guide is useless, of course. There are an enormous number of buildings which meet the unstated assumptions and for which it would serve as a good start on field investigation. The lesson, as always, is to start with the building at hand and then see which tool is appropriate for analysis.
* “Material retraction” instead of “shrinkage,” and “repression at the foundation” instead of “settlement” are not terrible and do not make it impossible to get the author’s meaning, but discussing engineering in non-technical language is difficult enough without using non-standard terminology.
** Or at least modernish concrete buildings that follow the basic construction and design patterns in use for the last fifty years or so.
*** Actually, this is a bit unclear. His diagrams for “Cracks on slabs due to insufficient positive reinforcement” and “Cracks on slabs due to excessive overload” clearly show flat-slab construction, but the small axonometric of the building seems to show beams on the right side more closely spaced than the columns. There’s a form of flat-slab construction that has beams on the column lines, but it’s unpopular because it combines the negative aspects of two-way construction with the negative aspects of beam and one-way slab construction.
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