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SUMMARYThe e ects of soil-structure interaction in yielding systems are evaluated, including both kinematic and inertial interaction. The concepts developed previously for interacting elastic systems are extended to include the non-linear behavior of the structure. A simple soil-structure system representative of codedesigned buildings is investigated. The replacement oscillator approach used in practice to account for the elastic interaction e ects is adjusted to consider the inelastic interaction e ects. This is done by means of a non-linear replacement oscillator deÿned by an e ective ductility together with the known e ective period and damping of the system for the elastic condition. To demonstrate the e ciency of this simpliÿed approach, extensive numerical evaluations are conducted for elastoplastic structures with embedded foundation in a soil layer over elastic bedrock, excited by vertically propagating shear waves. Both strength and displacement demands are computed with and without regard to the e ect of foundation exibility, taking as control motion the great 1985 Michoacan earthquake recorded at a site representative of the soft zone in Mexico City. Results are properly interpreted to show the relative e ects of interaction for elastic and yielding systems. Finally, it is demonstrated how to implement this information in the context of code design of buildings.

The Manual of Civil Structures (MOC), a model design code in Mexico, has been in the process of being updated, and the new version of this code was published in 2008. A major update from the 1993 version was performed in the chapter for the seismic design of building structures. This paper summarizes the most relevant changes of this building code and their relation to research efforts conducted within Mexico and worldwide to improve the seismic design of building structures. One goal is to make the guidelines as transparent as possible to users, so that the design process will be clearer to structural engineers.

SUMMARYA numerical solution for evaluating the effects of foundation embedment on the effective period and damping and the response of soil-structure systems is presented. A simple system similar to that used in practice to account for inertial interaction effects is investigated, with the inclusion of kinematic interaction effects for the important special case of vertically incident shear waves. The effective period and damping are obtained by establishing an equivalence between the interacting system excited by the foundation input motion and a replacement oscillator excited by the free-field ground motion. In this way, the use of standard free-field response spectra applicable to the effective period and damping of the system is permitted. Also, an approximate solution for total soil-structure interaction is presented, which indicates that the system period is insensitive to kinematic interaction and the system damping may be expressed as that for inertial interaction but modified by a factor due to kinematic interaction. Results involving both kinematic and inertial effects are compared with those obtained for no soil-structure interaction and inertial interaction only. The more important parameters involved are identified and their influences are examined over practical ranges of interest. 1998 John Wiley & Sons, Ltd.

In order to explain damage and observed ground motions in Mexico City during the 1985 Michoacán earthquake, simultaneous consideration must be given to source, path, and site conditions. This is clear from teleseismic records and local vertical displacements. Incident waves had an important part of energy in the frequency band of 0.3-1 Hz. Damage distribution and observed motion in the lake bed zone cannot be satisfactorily explained using one-dimensional theory. The effects of lateral irregularities are required. To assess its effects we describe the stratigraphic setting of the valley and discuss some features of damage distribution with results for one- and two-dimensional wave propagation models. These are useful to establish on quantitative basis the importance of lateral heterogeneity.