Heuristic dimensioning criteria for timber elements in bending in the 18th and 19th centuries

This article investigates the heuristic rules adopted in the 18thcentury in dimensioning wooden elements. Data related to cross section and span are possibly collected for the first time in a table format in the L´Architecture pratique, published in 1691 by Pierre Bullet. The focus is on the design criteria of elements in bending adopted before the formalization of structural mechanics theory by Claude-Louis Navier. In particular, this study aims at investigating the rules that have been guiding carpenters in beam dimensioning. The treatise by Bullet had been reprinted many times and had been widely circulated. In the following decades, many other authors reported the same values in a table format. The wide acceptance of the treatise prompted the author to study the table in depth and to make an attempt in finding a rule that could fit the relationship between data. For this purpose, several attempts have been made based on the supposed knowledge of the 18thand 19thcentury carpenters. The analysis considered both the rule by Galileo Galilei and plainer interpretation attempts between the data sets. Heuristic dimensioning rules reported in the most popular architectural treatises based mainly on geometric proportions were also considered. In addition, both ultimate and serviceability limit state verifications according to Eurocode 5 have been performed to compare traditional and current timber design codes.