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The resistant shear force of 13 buildings severely damaged by the 1985 Mexico City earthquake was determined by static and dynamic analyses. The results of the static analysis suggest the advisability of increasing the shear base coefficient of the 1987 Mexico City building code RDF87 from 0.4 to 0.6 in the high seismicity zones of the area. The results of the dynamic analysis show that in order to obtain the same safety level, the maximum ordinate of the design spectrum should be larger than the base shear coefficient used with the static method, leading to a 0.8 maximum ordinate for Mexico City. When the resistant shear force is plotted as a function of the natural period of each building, the response spectrum obtained is very similar to the inelastic spectrum derived from the accelerograms, considering 5% critical damping, a ductility factor of 4 and degradation in resistance from 5% to 10%. Based on these results, new design spectra are proposed for use in the high seismicity zones in Mexico City.

This paper describes the study of a twelve floor concrete building with a waffle slab system located 300 meters from the accelerometer at Secretaria de Comunicaciones y Transportes (S.C.T) in Mexico City. First, the reduced seismic coefficient associated with the failure of the critical story is calculated by a linear dynamic analysis which reproduces the damage provoked by the 1985 earthquake to the real structure. Second, the ductility factor associated with the damaged stories is obtained through a step-by-step non-linear dynamic analysis. Finally, the peak value of the S.C.T. maximum ordinate for spectral response corresponding to 5 percent of critical damping was determined from this analysis.

We address the robust matching of lines between two views, when camera motion is unknown and dominant planar structures are viewed. The use of viewpoint noninvariant measures gives a lot of nonmatched or wrong matched features. The inclusion of projective transformations gives much better results with short computing overload. We use line features that can usually be extracted more accurately than points, and they can be used in cases where there are partial occlusions. In the first stage, the lines are matched to the weighted nearest neighbor using brightness and geometric-based image parameters. From them, robust homographies can be computed, which allows us to reject wrong matches and to add new good matches. When two or more planes are observed, the corresponding homographies can be computed and they can be used to obtain also the fundamental matrix, which gives constraints for the whole scene. The simultaneous computation of matches and projective transformations is extremely useful in many applications. It can be seen that the proposal works in different situations requiring only a simple and intuitive parameter tuning.