This article presents a complete cost-optimized design for rectangular isolated footings (RIFs) under biaxial bending with a partially compressed contact area (PCCA) and an eccentric column, i.e., part of the base is in contact with the soil (generating compression), and the other part is not in contact with the soil (generating neither compression nor tension), and the soil pressure behaves linearly. The proposed model is presented by integration to find the moments in the critical sections, the bending shears in the critical sections and the punching shear acting on the RIF, and these are compared with those that must be resisted according to the standards (ACI 318-19) Some articles show complete designs for RIFs with a fully compressed contact area (FCCA) and an eccentric column, and other articles show only the minimum area (A_min) for RIFs with a PCCA and an eccentric column. The main contributions of this article are as follows: (1) the A_min is determined from the loads and moments, assuming that the loads and moments it resists must be greater than or equal to those acting on the RIF; (2) the minimum cost (C_min) is determined. Three numerical studies are described to demonstrate the advantages of this study over other models. The results indicate that, according to the studies presented in this article, savings of up to 45.99% for A_min and 93.62% for C_min can be achieved using the model proposed in this article (MPA); this occurs when the pressure acting on the foundation does not reach the maximum available soil pressure (p_max). Therefore, this paper could be of great use to engineers dedicated to the construction of foundations.

Las lagunas anaerobias realizan la remoción de materia orgánica en ausencia de oxígeno y deben diseñarse considerando lagunas facultativas o aireadas, con el fin de continuar con el tratamiento y a la vez re oxigenar el agua residual. El propósito del presente documento es determinar dos gráficas para calcular la eliminación de coliformes fecales. Se incluye un ejemplo de aplicación con el método tradicional adoptado por el Instituto Mexicano de Tecnología del Agua y la Comisión Nacional del Agua, posteriormente se utilizan las gráficas elaboradas previamente. Los resultados muestran los mismos valores calculados con el criterio tradicional.