Vaulted Earthen Floor Systems for Low-Cost Housing Construction

Abstract

This thesis explores the viable geometries of earthen vaulted floor systems for low-cost residential construction. Typical structural floor systems consist of a reinforced concrete flat slab, which is problematic as concrete and steel are expensive, carbon-intensive materials. As urbanization rates increase globally, informal and structurally inadequate settlements become more ubiquitous as a result. Vaulted structural floor systems can be constructed from earthen bricks to reduce cost and environmental impact. This thesis aims to investigate equilibrium solutions of barrel-vaulted structures through the use of local earth materials in emerging economies, with a particular focus in Central and South America.

While artisans have been constructing vaults for centuries as roofing systems, this thesis investigates the highly indeterminate structural behavior and design of shell structures to broaden the scope of their application such that they can also serve as floor systems. Through the lower bound principles of masonry structural design, the spanning limits of this structural form are presented for adobe, compressed earth blocks (CEB), and compressed stabilized earthen brick (CSEB). The analysis of unreinforced masonry vaults is further explored in three dimensions through form finding methodologies that implement linear optimization to investigate viable load paths within a defined area under specified boundary conditions. The application of three-dimensional analysis introduces two-way behavior within the vault, decreasing the reaction forces, and ultimately reducing the cost of construction. This thesis shows the range of possible spans using unfired adobe, CEB, and CSEB for vaulted earthen floor systems in the residential sector.