Yamile S. Rodriguez1, Giuliana Cardani2, Dario A. Coronelli2, and Thomas E. Boothby3
1)  Carrasquillo Associates
5113 Southwest Pkwy #250, Austin, TX 78735, USA
e-mail: ysr@carrasquilloassociates.com
2)  Dept. of Civil and Environmental Engineering, Politecnico di Milano
Piazza L. da Vinci, 32, Milano, Italy
e-mail: {giuliana.cardani,dario.coronelli}@polimi.it
3)  Department of Architectural Engineering, The Pennsylvania State University
104 Engineering Unit A, University Park, PA 16802
e-mail: teb2@psu.edu

Keywords: Lombardy, Romanesque, Gothic, Buttress, Proportions.

Abstract. A native system of brick construction flourished in Lombardy during the twelfth and thirteenth centuries [1]. The churches built according to this system have heavy-ribbed, quadripartite vaults, and usually have two aisle bays per nave bay. The use of iron tie rods was systematic during the construction and these features are still present. In this study, we investigate the proportions of the solid, trapezoidal buttresses characteristic of this system. These buttresses are built over the aisle vaults, rise above the level of the aisle roof, and extend to the ground outside the aisle walls. The buttresses at the Duomo di Milano have identical features. Based on an investigation of the buttresses at Milano and in the outlying regions of Lombardy, we find that they observe a specific, identifiable proportional rule. The dimensional rules for these buttresses resemble the proportions of a canonical equilateral triangle. This construction system paved the way for the adaptation of the gothic style in Italy: The Lombard system gave rise to the system used in the later, primarily gothic work at the Duomo of Milano. The system of vaulting was probably exported to Tuscany and adapted to the needs of Santa Maria Novella and later gothic works [2].