» عنوان : Soil-Structure Interaction for Building Structures
» عنوان : اندرکنش خاک سازه بر سازه
تعداد صفحات : ۲۹۲
The response of a structure to earthquake shaking is affected by interactions between three linked systems: the structure, the foundation, and the soil underlying and surrounding the foundation (FEMA, 2009). Soil-structure interaction analysis evaluates the collective response of these systems to a specified ground motion. The terms Soil-Structure Interaction (SSI) and Soil-Foundation-Structure Interaction(SFSI) are both used to describe this effect in the literature. In this report, the foundation is considered part of the structure, and the term SSI has been adopted. This report presents a synthesis of the body of knowledge contained in SSI literature, which has been distilled into a concise narrative and harmonized under a consistent set of variables and units. Specific techniques are described by which SSI phenomena can be simulated in engineering practice, and recommendations for modeling seismic soil-structure interaction effects on building structures are provided. 1.1 Background and Objectives Problems associated with the practical application of SSI for building structures are rooted in a poor understanding of fundamental SSI principles. Soil-structure interaction topics are generally not taught in graduate earthquake engineering courses, so most engineers attempting SSI in practice must learn the subject on their own. Unfortunately, practice is hindered by a literature that is often difficult to understand, and codes and standards that contain limited guidance. Most articles rely heavily on the use of wave equations in several dimensions and complex arithmetic to formulate solutions and express results. Moreover, nomenclature is often inconsistent, and practical examples of SSI applications are sparse. This gives rise to the present situation in which soil-structure interaction is seldom applied, and when it is, modeling protocols vary widely and are not always well conceived. Although the NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures has provided guidance for consideration of SSI effects in forced-based procedures for several decades, these procedures have not found significant use in practice. Practical application of SSI gained momentum following publication of FEMA 440, Improvement of Inelastic Seismic Analysis Procedures (FEMA, 2005), which provided the design community with procedures for incorporating the effects of soil-structure interaction in nonlinear static pushover-type analyses. These procedures were eventually adopted into ASCE/SEI 41-06,Seismic Rehabilitation of Existing Buildings (ASCE, 2007). Because they were developed for nonlinear static analysis, however, they were not directly applicable to response history analysis, which requires more careful consideration of specific components of soil-foundation interaction and the manner by which input ground motions should be applied to structural models. In 2009, the National Institute of Standards and Technology (NIST) initiated the Task Order 69221 Project entitled “Improved Procedures for Characterizing and Modeling Soil-Structure Interaction for Performance-Based Seismic Engineering.” The purpose of this project was to develop consensus guidance for implementing soil-structure interaction in response history analyses, such that input ground motions accurately reflect the input at the base of structures, and that structural models include elements that account for the geotechnical and foundation conditions associated with the building under consideration. Work also included an extensive review of available research on soil-structure interaction, evaluation of existing SSI guidelines for static-type analyses, and development of recommendations for improvement where necessary.