Olga Río

Calculation of chloride diffusivity in concrete from migration experiments, in non steady-state conditions

Abstract Shortening of the testing time to characterize concrete resistance to chloride penetration was the main practical improvement of the so called “Rapid Chloride Permeability Test” developed by Whiting. Recently, numerous papers were published presenting results using this method already standarized by AASHTO, although the claims on its real meaning are also numerous. In a previous paper, a solution for calculating ionic diffusivity from a migration test performed under steady-state conditions was presented based in the known Nernst-Planck equation which models mass transport in electrolytes. Some simplifying assumptions were made in order to solve the particular case of concrete. In the present paper, a solution is presented for non-stationary conditions also assuming the same simplifying conditions. The solution refers to a mathematical expression similar to that of simple diffusion, but considering ZFΔE/RT as the multiplying factor. Results from preliminary tests are presented which confirm the promising procedure of accelerated diffusion tests. Finally, calculation of the diffusion coefficient from concrete electrical resistance values is justified.

Heuristic method to check the realisability of a graph into a rectangular plan

Abstract The problem of mapping a graph into rectangles so that they cover a rectangular plan is considered. The graph may represent the basic scheme of a house or of a building, in which different design requirements are collected. To cope with this problem the authors have chosen a three steps approach: determining whether a graph can be mapped in this way (first step); automatically generating some of its realisations (second step); then how a given plan can be reduced to the rectangular one is analysed (third step). A heuristic approach to the general solution of the first step is proposed. It is a problem with a practical application in areas such as architectural design or compacting of electronic circuits, to which no general solution has been found in the specialised bibliography.

A computer-based teaching tool for structural design

In this paper we will discuss the importance of computer-based simulation tools for the education of architects and civil engineers. We present our efforts to develop a program for the simulation of structures (CASDET). CASDET forms a microworld for planar structures. The program enables students to compose structures and to experiment interactively the effects of different geometry and load configurations (see Fig. 1). It tries to identify the proposed structure and controls its stability. Upon request of the student, it also processes displacements, internal forces (moments, shear forces, etc.) and reaction forces on supports. The students can then visualise the desired information by interacting directly with the structure or its members of interest. We present different methods with which students can visualise the results of their actions and discuss their implications in the educational context.