Soil–structure interaction in yielding systems

Abstract

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.

Performance-based seismic design of flexible-base multi-storey buildings considering soil–structure interaction

“…In this study, an iterative method was used to calculate appropriate strength demands F tot (defined as the sum of the storey strengths) for the SSI systems to achieve a prescribed ductility  t , while maintaining the initial pattern of the strength distribution. It should be noted that storey ductility does not increase monotonically when reducing the strength [9], which means that there could be more than one strength satisfying a given ductility. In this case, only the highest strength was considered [39].…”

“…It has been generally accepted that the predominant period of the site motion plays an important role in SSI analyses [8,9]. Beneficial SSI effects have been found for structures with natural periods higher than the site period, whereas detrimental effects are observed in structures whose periods are shorter than the site period.…”

Estimation of inelastic displacement demands of flexible-based structures on soft soils

“…To take into account the nonlinear behaviour of the structural system, either a nonlinear EFSDOF or an equivalent linear EFSDOF oscillator can be used to simplify the SSI procedures. In additional to T ssi and ξ ssi , a nonlinear EFSDOF oscillator is characterised by an effective ductility ratio of μ ssi defined as (Avilés and Pérez-Rocha, 2003):…”

Revisions to Code Provisions for Site Effects and Soil-Structure Interaction in Mexico

“…By equating the maximum plastic deformation of an elastoplastic replacement oscillator with that developed in the SSI system under monotonic loading, the system ductility is found as (Avilés & Pérez-Rocha, 2003) Fig. 8.…”