Mathematical Modeling for the Optimal Cost Design of Circular Isolated Footings with Eccentric Column

This article shows a model for the design of circular isolated footings and the column placed anywhere in the footing under minimum cost criteria. Some designs for obtaining the diameter, effective depth, and steel areas of the footing under biaxial bending assume the maximum and uniform pressure at the bottom of the footing supported on elastic soils. All these works consider the column placed at the center of the footing. Three numerical problems are given (each problem presents four variants) to determine the lowest cost to design the circular footings under biaxial bending. Problem 1: Column without eccentricity. Problem 2: Column with eccentricity in the direction of the X axis of one quarter of the diameter of the footing. Problem 3: Column placed at the end furthest from the center of the footing on the X axis. The results are verified by the balance of moments, one-way shear or shear and two-way shear or punching. The new model shows a saving of 17.92% in the contact area with soil and of 31.15% in cost compared to the model proposed by other authors. In this way, the proposed minimum cost design model for circular footings will be of great help for the design when the column is placed on the center or edge of the footing

Susceptibility to Pitting Corrosion of Ti-CP2, Ti-6Al-2Sn-4Zr-2Mo, and Ti-6Al-4V Alloys for Aeronautical Applications

Titanium alloys are used in different industries like biomedical, aerospace, aeronautic, chemical, and naval. Those industries have high requirements with few damage tolerances. Therefore, they are necessary to use materials that present fatigue, mechanical, and corrosion resistance. Although Ti-alloys are material with high performance, they are exposed to corrosion in marine and industrial environments. This research shows the corrosion behavior of three titanium alloys, specifically Ti CP2, Ti-6Al-2Sn-4Zr-2Mo, and Ti-6Al-4V. Alloys were exposed on two electrolytes to a 3.5 wt % H2SO4 and NaCl solutions at room temperature using cyclic potentiodynamic polarization (CPP) and electrochemical noise (EN) according to ASTM G61 and ASTM G199 standards. CPP technique was employed to obtain electrochemical parameters as the passivation range (PR), corrosion type, passive layer persistence, corrosion potential (Ecorr), and corrosion rate. EN was analyzed by power spectral density (PSD) in voltage. Results obtained revealed pseudopassivation in CPP and PSD exposed on NaCl for Ti-6Al-2Sn-4Zr-2Mo, indicating instability and corrosion rate lower. However, Ti-6Al-4V presented the highest corrosion rate in both electrolytes. Ti-6Al-2Sn-4Zr-2Mo revealed pseudopassivation in CPP and PSD in NaCl, indicating a passive layer unstable. However, the corrosion rate was lower in both solutions