Frequency-Domain Analysis of Long-Span Bridges Subjected to Nonuniform Seismic Motions

Ettouney, Mohammed M.; Hapij, Adam; Gajer, R. B.

doi:10.1061/(asce)1084-0702(2001)6:6(577)

Cited by 8 publications

(4 citation statements)

References 13 publications

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“…Zerva [57,58] reached a similar conclusion for the case of N-support continuous beams excited by partially correlated motions, with the second study additionally considering the wave passage effect. Contribution of anti-symmetric modes to the total response has also been observed for asynchronously excited suspension [14,15,60] and arch [15] bridges. Studies based on THA further revealed the de-amplification of symmetric modes, particularly of the first transverse one in most cases, and the respective amplification of the antisymmetric ones in the case of straight [1,9,10,47,54,[61][62][63], curved [10,44] and cable-stayed [3,50,64] bridges.…”

Section: Introductionmentioning

confidence: 62%

Simplified design of bridges for multiple-support earthquake excitation

Papadopoulos

Sextos

2020

Soil Dynamics and Earthquake Engineering

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This paper presents a novel, bridge-dependent approach for quantifying the increase of design quantities due to spatially variable earthquake ground motion (SVEGM). Contrary to the existing methods for multiple support bridge excitation analysis that are either too complicated to be applied by most practitioners or oversimplied (e.g. Eurocode 8, Annex D provisions), this method aims to strike a balance between simplicity, accuracy and computational efficiency. The method deliberately avoids generating support-dependent, acceleration or displacement, asynchronous inputs for the prediction of bridge response. The reasons behind this decision are twofold: (a) first, the uncertainty associated with the generation of asynchronous motion scenarios, as well as the exact soil properties, stratification and topography is high while, (b) the response of a bridge is particularly sensitive to the above due to the large number of natural modes involved. It is therefore prohibitive to address SVEGM effects deterministically in the framework of a design code. Instead, this new method is based on two important and well-documented observations: (a) that SVEGM is typically globally beneficial but locally detrimental [1], and (b) that the local seismic demand increase is very closely correlated with the excitation of higher modes, which are not normally activated in the case of uniform ground motion [2,3]. Along these lines, a set of static analyses are specified herein to complement the standard, code-based response spectrum analysis. These static analyses apply spatially distributed lateral forces, whose patterns match the shape of potentially excited antisymmetric modes. The amplitude of those forces is derived as a function of the expected amplification of these modes according to the process initially proposed by Price et al. [4]. Two real bridges with different structural configurations are used as a test-bed to demonstrate the effectiveness of the new method. Comparison of the results with those obtained through rigorous response history analysis using partially correlated, spatially variable, spectrum-compatible input motions [5] shows that, the simplified method presented herein provides a reasonably accurate estimation of the SVEGM impact on the response of the bridges examined at a highly reduced computational cost. This is essentially an elastic method that is found to be simple, yet precise enough to consist an attractive alternative for the design and assessment of long and/or important bridge structures in earthquake-prone regions.

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Section: Introductionmentioning

confidence: 62%

Simplified design of bridges for multiple-support earthquake excitation

Papadopoulos

Sextos

2020

Soil Dynamics and Earthquake Engineering

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“…The analysis point that the method is more effective in terms of the number of unknowns and it has higher accuracy. On the other hand, the frequency analysis may be a strong tool to exhibit larger redistribution of responses in case of nonuniform seismic motions [8].…”

Section: Introductionmentioning

confidence: 99%

Seismic Responses of an Isolated Long-span Bridge using Frequency Domain and Time Dependent Procedures

Sarıtaş

Hasgür

2023

Turkish Journal of Civil Engineering

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Seismic behavior of an isolated bridge is analyzed in the frequency domain under the effects of nonstationary ground motions. For dynamic solutions, different ground environments are considered by simulating nonstationary quakes that can be represented from bedrock to soft ground level. In the simulations, power spectral functions and filtered white noise model are adopted for spectral densities of the earthquake excitations. Various computer algorithms have been developed for earthquake simulations, establishing the bridge finite element model and stochastic solutions. Twenty simulated ground motions are used for each soil profile and the parameters of Rayleigh dispersion are estimated by evaluating the system responses for each ensemble. A number of peak response factors dependent on soil conditions are presented for seismic responses. In addition, extreme value distributions of the responses are shown with the probability of exceeding functions and tables. The responses are discussed for the specific exceedance level of probabilities used in probabilistic design process. The stochastic analyses generally yielded responses consistent with time domain solutions. Exceedance probability functions of the peak responses were obtained in a close relationship. However, the probability distributions of the responses decomposed for the soft soil case and they displayed a wider dispersion even for low exceedance levels. The peak responses are expressed with some exceedance probabilities. In the estimation of response variations, this study showed the practicality of the frequency domain method and the results revealed higher peak response factors and variances for softer soil conditions. Furthermore, this study indicated that the frequency domain procedure is an effective tool in the obtaining of nonstationary seismic responses.

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“…Der Kiureghian and Neuenhofer [6] and Loh and Ku [7] developed methods of analysis that employ the response spectrum speciÿcation of the seismic acceleration and accurately account for the e ect of the partial correlation of the input motion. Other researchers [8][9][10][11][12][13] performed sensitivity analyses of the seismic response of bridges to partially-correlated ground motion. These papers show that fully-correlated motions may produce higher or lower responses than partially-correlated motions depending on the dynamic characteristics of structures, on the considered e ects and on the cross-correlation between support motions.…”

Section: Introductionmentioning

confidence: 99%

Seismic response of multi‐supported structures by proper orthogonal decomposition

Tubino

Carassale

Solari

2003

Earthq Engng Struct Dyn

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SUMMARYThe seismic analysis of structures is usually carried out considering the ground motion as fully-correlated in space and determining the structural response by pseudo-deterministic methods such as the response spectrum technique. Actually, the partial correlation of the seismic acceleration may in uence heavily the behaviour of spatially extended structures, such as bridges, viaducts or pipelines. In order to take its partial correlation into account, the seismic ground motion is schematized as a stochastic process dependent on time and on space; the hypotheses of stationarity and homogeneity are used to obtain simple and general results. The in uence of the partial correlation of the seismic ground motion on the structural response is investigated by introducing suitable Equivalent Spectra. The acceleration of the support-points of the structure is represented by the Proper Orthogonal Decomposition (POD), deÿning the modes of the earthquake. The method is formulated for any kind of multi-degree-of-freedom system and is applied, as a case study, to an ideal single-storey multi-supported frame with an axially rigid beam. In the case of two supports, the POD decouples the pseudo-static and the dynamic contributions to the structural response. This property is preserved for structural systems with many supports, where only the lower modes of the earthquake, usually the ÿrst two POD modes, are responsible for the structural response.

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Frequency-Domain Analysis of Long-Span Bridges Subjected to Nonuniform Seismic Motions

Cited by 8 publications

References 13 publications

Simplified design of bridges for multiple-support earthquake excitation

Simplified design of bridges for multiple-support earthquake excitation

Seismic Responses of an Isolated Long-span Bridge using Frequency Domain and Time Dependent Procedures

Seismic response of multi‐supported structures by proper orthogonal decomposition

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