Floor Accelerations in Yielding Special Moment Resisting Frame Structures

Summary This study uses instrumented buildings and models of code‐based designed buildings to validate the results of previous studies that highlighted the need to revise the ASCE 7 Fp equation for designing nonstructural components (NSCs) through utilizing oversimplified linear and nonlinear models. The evaluation of floor response spectra of a large number of instrumented buildings illustrates that, unlike the ASCE 7 approach, the in‐structure and the component amplification factors are a function of the ratio of NSC period to the supporting building modal periods, the ground motion intensity, and the NSC location. It is also shown that the recorded ground motions at the base of instrumented buildings in most cases are significantly lower than design earthquake (DE) ground motions. Because ASCE 7 is meant to provide demands at a DE level, for a more reliable evaluation of the Fp equation, 2 representative archetype buildings are designed based on the ASCE 7‐16 seismic provisions and exposed to various ground motion intensity levels (including those consistent with the ones experienced by instrumented buildings and the DE). Simulation results of the archetype buildings, consistent with previous numerical studies, illustrate the tendency of the ASCE 7 in‐structure amplification factor, [1 + 2(z/h)], to significantly overestimate demands at all floor levels and the ASCE 7 limit of ap=212 to in many cases underestimate the calculated NSC amplification factors. Furthermore, the product of these 2 amplification factors (that represents the normalized peak NSC acceleration) in some cases exceeds the ASCE 7 equation by a factor up to 1.50.

Section: Introductionmentioning

confidence: 99%

Evaluation of ASCE 7 equations for designing acceleration‐sensitive nonstructural components using data from instrumented buildings

Anajafi

Medina

2017

“…It is reasonably highlighted in past studies that floor amplification is strongly dependent on the dynamic characteristics of the supporting structure and torsional response of the supporting structure leads to increased floor acceleration demands at the FE . Hill‐side buildings have signifcantly different structural configuration as compared with regular buildings located on plane topography, resulting in significantly different dynamic chracteristics while also exhibiting torsional effects in the across‐slope direction .…”

Section: Background Studiesmentioning

confidence: 96%

“…Past studies on the evaluation of floor acceleration demands can be broadly classified under the categories of studies based on both single‐degree‐of‐freedom and multiple‐degree‐of‐freedom modeling of the supporting structure. The parameters affecting the floor response, identified in these studies, include the dynamic characteristics (periods and mode shapes) of the supporting structure, the input seismic ground motion characteristics, and the inelasticity (ductility demand) of the supporting structure . Some of the recent studies on evaluation of the floor acceleration demands aimed at developing probabilistic models for considering the record‐to‐record variability of the floor response …”

Section: Background Studiesmentioning

confidence: 99%

“…Accordingly, in the present study, the floor response of hill‐side buildings is examined by using a series of linear time‐history analyses. It is well recognized that the level of inelasticity (ductility demand) on a building has a significant influence on the floor amplification; however, the present study is focused only on the effect of dynamic characteristics of the hill‐side buildings. The effect of ductility demand on floor amplification in hill‐side buildings is currently under investigation by the authors in a separate study.…”

Section: Background Studiesmentioning

confidence: 99%

See 1 more Smart Citation

Effect of irregular structural configuration on floor acceleration demand in hill‐side buildings

Surana

Singh

Lang

2018

Summary A suite of reinforced‐concrete frame buildings located on hill sides, with 2 different structural configurations, viz step‐back and split‐foundation, are analyzed to study their floor response. Both step‐back and split‐foundation structural configurations lead to torsional effects in the direction across the slope due to the presence of shorter columns on the uphill side. Peak floor acceleration and floor response spectra are obtained at each storey's center of rigidity and at both its stiff and flexible edges. As reported in previous studies as well, it is observed that the floor response spectra are better correlated with the ground response spectrum. Therefore, the floor spectral amplification functions are obtained as the ratio of spectral ordinates at different floor levels to the one at the ground level. Peaks are observed in the spectral amplification functions corresponding to the first 2 modes in the upper portion of the hill‐side buildings, whereas a single peak corresponding to a specific kth mode of vibration is observed on the floors below the uppermost foundation level. Based on the numerical study for the step‐back and split‐foundation hill‐side buildings, simple floor spectral amplification functions are proposed and validated. The proposed spectral amplification functions take into account both the buildings' plan and elevation irregularities and can be used for seismic design of acceleration‐sensitive nonstructural components, given that the supporting structure's dynamic characteristics, torsional rotation, ground‐motion response spectrum, and location of the nonstructural components within the supporting structure are known, because current code models are actually not applicable to hill‐side buildings.

“…Among them are [18][19][20] and [21], which are limited to elastic primary structures, whereas in [9,22,23] and [24], methods have been developed, which are also applicable to inelastic structures. Among them are [18][19][20] and [21], which are limited to elastic primary structures, whereas in [9,22,23] and [24], methods have been developed, which are also applicable to inelastic structures.…”

Section: Introductionmentioning

confidence: 99%

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

Vukobratović

Fajfar

2016

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.