Building Seismic Stability - Code Provisions vs. Inelastic Behavior

Published

June 30, 2024

Author(s)

Larry Fahnestock, Shitao Shi, Matthew Speicher

Abstract

In a building, seismic stability is provided when the internal restoring forces resist the effective earthquake forces plus the destabilizing effects of gravity that arise when the building displaces laterally. Although this concept can be succinctly stated, its implementation in building code provisions is not as straightforward. For example, many building codes simplify earthquake effects using static design forces that are reduced to consider the influence of inelastic response, and elastic analysis is used to proportion the building structural system. Although this approach has sound justification, it introduces confusion about incorporating the destabilizing effects of gravity, often called second-order or P-Δ amplification effects. Consideration of P-Δ effects varies around the world, but in the United States, the governing standard on loads stipulates a procedure to amplify structural demands using elastic lateral displacements. Although this simplified strategy, which does not consider inelastic lateral displacements that will occur during a large earthquake, typically leads to a modest increase in strength and stiffness of the building structural system, it is not fundamentally linked to enhanced earthquake performance. In addition, the situation is further complicated by other design requirements, such as drift limits and ductile detailing, that may significantly influence strength and stiffness of the building structural system and obscure the P-Δ amplification aspects of the design process. Recent research on seismic stability behavior and design of steel building systems illustrates the relative influence of key parameters and provides insight into considering P-Δ effects in a manner that is linked to inelastic earthquake response.

Proceedings Title

Proceedings of the 18th World Conference on Earthquake Engineering

Conference Dates

June 30-July 5, 2024

Conference Location

Milan, IT

Conference Title

18th World Conference on Earthquake Engineering

Pub Type

Conferences

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Keywords

seismic, building, stability, steel

Citation

Fahnestock, L. , Shi, S. and Speicher, M. (2024), Building Seismic Stability - Code Provisions vs. Inelastic Behavior, Proceedings of the 18th World Conference on Earthquake Engineering, Milan, IT, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956966 (Accessed April 30, 2025)