Apparent Periods of a Building. I: Fourier Analysis

Trifunac, Mihailo D.; Ivanović, S.S.; Todorovska, Maria I.

doi:10.1061/(asce)0733-9445(2001)127:5(517)

Cited by 134 publications

(86 citation statements)

References 12 publications

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“…For earthquake engineering purposes, dynamic properties identified from such tests provide invaluable data as they represent the dynamic properties of the structure during an actual ground shaking event. As mentioned previously, these properties have been shown to vary with the amplitude of the ground shaking (McVerry, 1979;Trifunac et al, 2001a). However, in areas of moderate seismicity, such tests may require considerable patience since the occurrence of significant earthquake shaking may be quite rare.…”

Section: Earthquake Response Testsmentioning

confidence: 90%

“…Finally, several studies have shown that the fundamental periods of a building tend to increase with the level of excitation, from ambient to strong motions (Çelebi, 1996;Li and Mau, 1997;McVerry, 1979;Trifunac et al, 2001a;Trifunac et al, 2001b). This has generally been attributed to changes in effective building stiffness (due to cracking of RC members or participation of non-structural elements), foundation stiffness (due to softening of soils at large strains), or structural damage.…”

Section: Other Factors Affecting the Fundamental Periodmentioning

confidence: 99%

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In Situ Dynamic Characteristics of Reinforced Concrete Shear Wall Buildings

Gilles

McClure

2012

Structures Congress 2012

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Structural engineers routinely need to make assumptions about the dynamic properties (natural periods, mode shapes, and damping) of a building to simulate its response to dynamic loads, such as strong winds or earthquake ground motions. However, the assumed properties may significantly differ from those of the actual building, once it is constructed, due to differences between the idealized model and in situ conditions. The main objectives of this study are to evaluate how common models and assumptions used to predict the dynamic properties of buildings compare to those measured in actual buildings, and to develop improved prediction models.To this end, ambient vibration measurements were performed in 39 buildings on the island of Montréal and the dynamic properties of up to six vibration modes were identified, for each of these buildings, using the enhanced frequency domain decomposition method. Though the initial goal was to obtain a representative sample of different types of buildings, 27 of these 39 buildings turned out to be reinforced concrete buildings with shear walls providing the main resistance to lateral loads. Hence, the scope of this study was narrowed to the dynamic properties of reinforced concrete shear wall (RCSW) buildings. The measured dynamic properties of this subset of 27 buildings were then used to evaluate different models, proposed in building codes and in the literature, to predict the natural periods and damping characteristics of these types of buildings. Finally, simple models to predict the natural periods of torsion and second translation modes were proposed based on regression analyses. These models agree very well with those that have been proposed in the literature. Again, equations corresponding to different probability levels (mean, mean minus one standard deviation, and mean plus one standard deviation) were produced as a measure of uncertainty.This study should help engineers select realistic values of the dynamic properties of RCSW buildings for structural analysis and design, and should ultimately improve engineers' ability to predict the dynamic response of these buildings. Further, the proposed models could lead to improved recommendations in building codes.iii This research could not have been possible without the help of many building owners and managers, who allowed our team to perform vibration measurements in their buildings. I would also like to thank the numerous graduate and undergraduate students who were involved in these tests for both their participation and the stimulating discussions that often ensued:

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Section: Earthquake Response Testsmentioning

confidence: 90%

Section: Other Factors Affecting the Fundamental Periodmentioning

confidence: 99%

In Situ Dynamic Characteristics of Reinforced Concrete Shear Wall Buildings

Gilles

McClure

2012

Structures Congress 2012

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“…The bottom layer is taken to be ''soft,'' so that b 2 ¼ ffiffiffiffiffiffiffiffiffiffiffiffi m 2 =r 2 p ¼ 100 m=s, a value typical of experimentally determined shear-wave velocities in buildings [24,25].…”

Section: Excitation By Short Wavesmentioning

confidence: 99%

Response spectra for differential motion of columns paper II: Out-of-plane response

Trifunac

Gičev

2006

Soil Dynamics and Earthquake Engineering

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It is shown that the common response spectrum method for synchronous ground motion can be extended to make it applicable for earthquake response analyses of extended structures experiencing differential out-of-plane ground motion. A relative displacement spectrum for design of first-story columns SDC (T, T T , z, z T , t, d) is defined. In addition to the natural period of the out-of-plane response, T, and the corresponding fraction of critical damping, z, this spectrum also depends on the fundamental period of torsional vibrations, T T , and the corresponding fraction of critical damping, z T , on the ''travel time,'' t (of the waves in the soil over a distance of about one-half the length of the structure), and on a dimensionless factor d, describing the relative response of the first floor. The new spectrum, SDC, can be estimated by using the empirical scaling equations for relative displacement spectra, SD, and for peak ground velocity, v max . For recorded strong-motion acceleration, and for symmetric buildings, the new spectrum can be computed from Duhamel's integrals of two uncoupled equations for dynamics equilibrium describing translation and rotation of a two-degree-offreedom system. This representation is accurate when the energy of the strong-motion is carried by waves in the ground the wavelengths of which are one order of magnitude or more longer than the characteristic length of the structure. r

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“…While this scattered energy is smaller for actual foundations of buildings, because those are never as rigid as their mathematical models [54], the scattering from flexible foundations still plays an important role in bringing about pockets of nonlinear soil deformation, which then lead to increased effective compliances and to their asymmetry. Observations of the response of full-scale structures during strong earthquake shaking show indirectly how prominent these nonlinearities in the soil structure systems can be [24,[48][49][50][51]. Observations also show that these nonlinear deformations in the soil usually occur well before any damage begins in the buildings.…”

Section: Introductionmentioning

confidence: 99%

Energy dissipation by nonlinear soil strains during soil–structure interaction excited by SH pulse

Gičev

Trifunac

2012

Soil Dynamics and Earthquake Engineering

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a b s t r a c tThree variants of a two-dimensional (2-D) model of a building supported by a rectangular, flexible foundation embedded in nonlinear soil are analyzed. The building, the foundation, and soil have different physical properties. The building is assumed to be linear, but the foundation and the soil can experience nonlinear deformations. It is shown that the work spent for the development of nonlinear strains in the soil can consume a significant part of the input wave energy, and thus less energy is available for excitation of the building. The results help explain why the damage, during the 1994 Northridge earthquake in California, to residential buildings in the areas that experienced large strains in the soil was absent or reduced.

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Apparent Periods of a Building. I: Fourier Analysis

Cited by 134 publications

References 12 publications

In Situ Dynamic Characteristics of Reinforced Concrete Shear Wall Buildings

In Situ Dynamic Characteristics of Reinforced Concrete Shear Wall Buildings

Response spectra for differential motion of columns paper II: Out-of-plane response

Energy dissipation by nonlinear soil strains during soil–structure interaction excited by SH pulse

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