Estimating floor spectra in multiple degree of freedom systems

Summary This paper deals with floor acceleration spectra, which are used for the seismic design and assessment of acceleration‐sensitive equipment installed in buildings. In design codes and in practice, not enough attention has been paid to the seismic resistance of such equipment. An ‘accurate’ determination of floor spectra requires a complex and quite demanding dynamic response history analysis. The purpose of the study presented in this paper is the development of a direct method for the determination of floor acceleration spectra, which enables their generation directly from the design spectrum of the structure, by taking into account the structure's dynamic properties. The method is also applicable to inelastic structures, which can greatly improve the economic aspects of equipment design. A parametric study of floor acceleration spectra for elastic and inelastic single‐degree‐of‐freedom (SDOF) and multiple‐degree‐of‐freedom structures was conducted by using (non)linear response history analysis. The equipment was modelled as an elastic single‐degree‐of‐freedom system. The proposed method was validated by comparing the results obtained with the more accurate results obtained in a parametric study. Due to its simplicity, the method is an appropriate tool for practice. In the case of inelastic structural behaviour, the method should be used in combination with the N2 method, or another appropriate method for simplified nonlinear structural analysis. Copyright © 2016 John Wiley & Sons, Ltd.

Section: Introductionmentioning

confidence: 99%

A method for the direct estimation of floor acceleration spectra for elastic and inelastic MDOF structures

Vukobratović

Fajfar

2016

“…Any correction to better fit a specific spectral region may be defined by an interval in both key parameters. The implications of the input definition presented in this paper are certainly significant and may foster a radical change in design philosophy, although still within a general displacement‐based approach. Considering the progressive orientation of design toward damage limitations, it appears particularly intriguing to explore the possibility of a direct derivation of combined floor spectra Considering the results discussed in this paper and the potential extensions mentioned above, it is expected that the new input definition will result in noticeable implications on design and assessment.…”

Section: Discussionmentioning

confidence: 99%

Introducing new design spectra derived from Italian recorded ground motions 1972 to 2017

Calvi

Rodrigues

Silva

2018

Summary The shape of design spectra, traditionally based on regions characterized by constant displacement, constant velocity, and constant acceleration, has been discussed from a conceptual point of view by Calvi (2018). In the same study, a formulation for the definition of the design spectra relying on four parameters was proposed. Predictive models are proposed herein to calculate these four parameters, conditional on magnitude and distance. These models were developed using a large number of recorded ground motions in Italy, and they allow defining combined spectral acceleration versus spectral displacement plots. Such design spectra are shown to reasonably interpolate the experimental data, resulting in acceleration and displacement demand that approximate the response spectra resulting from +1σ results obtained from recorded ground motions. While it is recognized that numerous additional parameter should be considered (eg, focal depth and fault distance, site amplification), it is also concluded that this approach to define the seismic demand is promising toward a rationalization of seismic design. A thorough application of the approach developed and preliminary tested in this work may result in a re‐visitation of seismic design approaches and, ultimately, in a more efficient use of the available resources.

“…Furthermore, methods to estimate floor accelerations in buildings such as Calvi and Sullivan, 29 among others, rely on knowing the fundamental periods of vibration and associated mode shapes a priori. Furthermore, methods to estimate floor accelerations in buildings such as Calvi and Sullivan, 29 among others, rely on knowing the fundamental periods of vibration and associated mode shapes a priori.…”

Section: Identify Spectral Values At Slsmentioning

confidence: 99%

Conceptual seismic design in performance‐based earthquake engineering

O’Reilly

Calvi

2018

Summary A principal aspect of seismic design is the verification of performance limit states, which help ensure satisfactory behaviour within a performance‐based earthquake engineering framework. However, it is increasingly acknowledged that while ensuring life safety is a suitable basic design requirement, more meaningful metrics of seismic performance exist. Expected annual loss (EAL) has gained attention in recent years but tends to be limited to seismic assessment. This article proposes a novel conceptual design framework that employs EAL as a design tool and requires very little building information at the design outset. This means that designers may commence from a definition of required EAL and arrive at a number of feasible structural solutions without the need for any detailed design calculations or numerical analysis. This works by transforming the building performance definition to a design solution space using a number of simplifying assumptions. A suitable structural response backbone is subsequently determined and used to identify feasible building typologies and associated structural geometries. The assumptions made to implement such a conceptual design framework are discussed and justified herein followed by a case study application. This proposed design framework is intended to form the first step in seismic design to identify suitable typologies and layouts before subsequent member detailing and design verification. This way, engineers, architects, and clients can make more informed decisions that target certain performance goals at the beginning of design before further refinement.