EQUATIONS THAT DESCRIBE THE GEOMETRY OF SUPERADOBE DOMED STRUCTURES

Abstract

"Superadobe" is a method for the construction of self-built shelters that has three main advantages: It’s economical, it’s easy to execute by common people, and produces buildings with good structural behavior against natural events such as earthquakes, floods, fire and high winds [1]. It consists in filling polypropylene sacks with a moist mixture of clay, sand, gravel and lime/cement; placing and compacting one on top of another in the form of concentric rings of decreasing radii and describing a double curvature monolith. (Similar to a paraboloid). The construction of these domed monoliths follow a simple geometrical pattern based on the use of compasses, hence the form, and other building characteristics can be parametric. This is, a system of equations for these building’s physical dimensions can be derived, based on initial parameters. These equation’s variables can be divided into independent ('constructive') and dependent ('observable'), and by defining the values of the independent parameters (sack dimensions, radius of base (internal compass), radius of roof (external compass), radius of skylight, dimensions of openings, mean material specific weight, mean material elastic modulus, mean friction coefficient between rows, etc.), resulting dimensions and mechanical behaviors, such as building height, interior habitable area, proportion of rows that rest upon the previous, or total building weight, maximum shear force amongst all rows, axial stresses, etc. can be determined. This article deals with the resulting geometrical dimensions of the building, given corresponding initial parameters. If we were to set some dependent variables as fixed values, we could solve the system of equations for the missing independent parameters. This would allow for example, to set design values for building weight and height, and to determine the unknown values for the corresponding radiuses and necessary sack dimensions which will produce a building that meets this pre requisites. This paper briefly explains a geometrical model of Superadobe domed structures.