Multicomponent Ground Motions Research Articles

Seismic responses of transmission tower-line system under multi-component ground motions

In this study, shaking table tests, theoretical research, and finite element modeling analysis were conducted on seismic responses of a transmission tower-line system under multi-component ground motions. The rocking component of ground motion was determined from the original seismic record by the wavelet analysis. The shaking table tests for scale models (single tower and tower-line system) that satisfy the similarity ratio of an actual tower-line system, were performed under multiple directions of motion. Dynamic equations under multi-component (horizontal, coupled horizontal, and tilting (CHT), and coupled vertical, horizontal, and tilting (CVHT)) ground motions were first derived in theoretical studies. The finite element model based on the actual transmission tower line system was built, and the response of the system under the identical working condition was calculated. It is found that the rotational component of the ground motion cannot be overlooked and significantly impacts the seismic response of the tower-line system, which is reflected especially as the vertical motion is coupled. The tilting ground motion, the additional second-order effect, and the foundation tilting jointly cause the increase in the response amplitude and significant asymmetric displacement effect. Since this effect of tilting ground motions, the weakening effect of the transmission line to reduce the responses for the displacement and acceleration of the tower-line system is also weakened. It is, therefore, essential to consider the adverse effects of multi-component ground motions on the designing of transmission tower systems in high-intensity areas.

Global reliability evaluation of a high-pier long-span continuous RC rigid frame bridge subjected to multi-point and multi-component stochastic ground motions

High-pier long-span continuous RC rigid frame bridges would be more vulnerable to seismic spatial variability and multi-component nature due to their large geometric dimension. However, research on seismic performance of these bridges subjected to multi-point and multi-component ground motions is sparse. In this study, the unified expression of spectral decomposition integrating spectral representation method and proper orthogonal decomposition based on coherency function matrix is derived. Then the dimension-reduction representation is developed for sample realization of multi-point and multi-component non-stationary stochastic ground motions with merely three elementary random variables, which bypasses the challenges of high-dimensional randomness degree and huge computation expense faced by the Monte Carlo simulation scheme. Thereafter the accurate seismic response analysis of a high-pier long-span bridge is numerically scrutinized combining with the probability density evolution method to further expound the effectiveness of the dimension-reduction model. Finally, a heuristic global reliability evaluation strategy employing relative displacement angle of bridge pier segments as criterion is proposed inspired by the idea of equivalent extreme-value event. Benefiting from this, both the refined reliability evaluation of bridge members and the structural global reliability can be accomplished, providing the possibilities of quantitative seismic performance assessment and earthquake resistance optimization design from an overall perspective.

Feasibility evaluation of pre-pressed spring devices for vertical isolation of single-layer spherical lattice shell structures

Single-layer spherical lattice shells are typical spatial structures for large-scale landmarks and public buildings. If such buildings are located in strong-earthquake zones, their seismic resilience must be considered. Long-span spatial structures are highly sensitive to multi-component ground motions, and vertical ground shakings lead to strong structural vibrations. Although a few vertical isolators with invariant stiffness have been developed, they are generally too stiff to effectively isolate vertical seismic shakings. In this paper, a nonlinear vertical isolator using pre-pressed and restrained helical springs called pre-pressed spring device (PSD) is proposed. The main advantages of the PSD are that it not only provides a high first stiffness and large bearing force to support the weight of the isolated object but also possesses sufficiently low stiffness to isolate vertical ground motions. In a vertical isolation system, PSDs are employed as basic load-carrying elements, and viscous dampers can be introduced into the system to function as additional energy dissipation devices. The configuration, working principle, and mechanical model of the newly developed PSD are described and explained in detail. Cyclic loading experiments were performed on a prototype PSD to investigate its actual force–displacement relationship. The experimental results showed that the PSD specimen exhibited multilinear elastic behaviors with clear first and isolation stiffness properties. A novel numerical model of the PSD was constructed, and the accuracy of the model was validated by comparing the simulation and experimental results. Subsequently, PSD-damper assemblies and friction pendulum bearings (FPBs) were used to form three-dimensional (3D) isolation bearings for a single-layer spherical lattice shell with surrounding columns. The seismic responses of the controlled structure were evaluated using nonlinear time-history analysis. The numerical results revealed that the PSDs achieved effective static-load support and vertical isolation, and that the entire 3D isolation bearings significantly improved the seismic behavior of the lattice shell structures in all three directions.

Reconciling Eurocode 8 Part 1 and Part 2 Two-component Record Selection

ABSTRACT Eurocode 8 (EC8) allows the use of dynamic analysis for the design and assessment of structures and provides some constraints for the selection of acceleration time-histories as seismic input. However, when it comes to the selection of two-horizontal-component natural ground motion records, parts 1 and 2 of EC8, stipulate apparently different criteria. The first aim of this paper is to build up on previous studies and investigate whether this difference in provisions translates into the selection of systematically different sets of records. A series of record selection case-studies presented in this study, corroborate the preliminary findings of previous work, and show that this is not the case, that is, record sets chosen according to one group of criteria tend to satisfy the other by default. A second aim is to investigate the different options for selecting multi-component ground motion records in part 1, which turn out to be equivalent. Finally, a third issue tackled is the effect that different definitions of spectral acceleration, that the design spectrum refers to, can have on spectrum-compatible record selection, when two horizontal components are involved. The results indicate that, for some of these alternative definitions, such as maximum or random component spectral acceleration, sets obtained via direct spectrum compatibility may not always agree with a simple application of Eurocode 8 provisions. On the other hand, when spectral acceleration is defined as the geometric mean of the two components, consolidated record selection algorithms appear to guarantee spectrum compatibility.

Efficient selection of up to three-component ground excitation sets for earthquake engineering applications

Ground motion record selection methodologies are commonly developed to ensure that the input excitation used in response history analyses embodies essential conditions such as spectral compatibility, hazard and intensity measure consistency, seismological and site-specific criteria, always performing in a computationally efficient manner. A methodology utilizing genetic algorithms is revisited here, expanded to select multi-component ground motions and satisfying the typically required selection objectives of earthquake engineering applications, while ensuring increased efficiency. Multi-objective optimization is performed, claimed to be superior in delivering robust results that account for spectral compatibility in first and second order statistics (mean and standard deviation) in a wide range of spectral values, as well as satisfying seismological and site-specific criteria. A unique contribution is the ability to include probability distribution targets in specific ordinates of the spectrum, on top of the mean and standard deviation, allowing for more refined ground motion sets that can be used to reduce the number of records required in response history analyses. Additionally, a novel benchmarking process to assess the efficiency of ground motion record methodologies is introduced here, in terms of providing sets that are globally-optimal solutions to the optimization problem. Through this benchmarking algorithm, the proposed methodology appears to be impeccable in extracting the best possible ground motion sets.

Orientation of the strongest velocity pulses and the maximum structural response to pulse-like ground motions

The ground motion pulse-like effect depends on its orientation, it is thus necessary to identify the direction of the ground motion with the strongest pulse. A simple yet efficient method to identify the strongest pulse over all orientations in multicomponent ground motions is presented in this study, through rotating the ground motions to the orientation associated with the maximum peak ground velocity (PGV). It is demonstrated that the pulse-like ground motion components in the orientation with the maximum PGV value have the potential to produce the largest mean/median ductility than the components rotated to all remaining orientations. A comparison of the proposed methodology with an existing method is also performed, further demonstrating that the proposed maximum PGV methodology can accurately identify the strongest pulse. The determined strongest pulse can be utilized in engineering practice to estimate the maximum seismic demands on structures.

Experimental and numerical study of the spring-asphalt 3D isolation structures under multi-component ground motions

A low-cost spring-asphalt bearing for the 3D seismic base isolation of low-rise residences is presented in this paper. Its dynamic response under horizontal, vertical and rocking ground motions is studied by shaking table test. Different types of excitations such as horizontal excitation only, horizontal and vertical excitation, horizontal, vertical and rocking excitations with different peak ground accelerations are input. A numerical model is developed to further study the dynamic characteristics of buildings with spring-asphalt 3D isolation bearing under multi component ground motions. Frequency domain and time domain analysis are conducted to research dynamic responses of the model. The function of asphalt is also researched by contrast experiments. Research results show that the 3D isolation bearing could efficiently reduce horizontal and vertical acceleration response of upper structures. Furthermore, asphalt makes the structure possess good energy dissipation capability. In addition, the asphalt could provide considerable damping and reduce the displacement while does not add so much stiffness.

Reliability and fragility assessment of the mid- and high-rise wood buildings subjected to bidirectional seismic excitation

Often the estimation of reliability and fragility curve for a structure subjected to earthquake loading is carried out for unidirectional ground motions, even though the multicomponent ground motions can affect the seismic responses. A simple procedure to estimate the reliability of 3D bisymmetric buildings subjected to the bidirectional orthogonal ground motions is proposed in the present study. The procedure considers that the responses of a 3D bisymmetric building can be approximated by those of an equivalent nonlinear inelastic two-degree-of-freedom (2DOF) system. The parameters of the equivalent system are identified using the capacity surface of the buildings obtained through nonlinear static pushover analysis or incremental dynamic analysis. The procedure is applied to estimate the reliability and fragility of mid- and high-rise wood buildings subjected to bidirectional ground motions. A comparison of the estimated reliabilities and fragilities by considering uni- and bi-directional ground motions is given, showing the importance of considering the bidirectional ground motions. The results indicate that the failure probabilities under the bidirectional ground motions are greater as compared to those obtained under the unidirectional ground motions. Therefore, for assessing the reliability of building under the seismic ground motions, the consideration of bidirectional ground motion can be important for seismic risk modelling and emergency preparedness.

Erratum to An Efficient Algorithm to Identify Strong‐Velocity Pulses in Multi‐Component Ground Motions

Correction| October 22, 2019 Erratum to An Efficient Algorithm to Identify Strong‐Velocity Pulses in Multi‐Component Ground Motions Shrey K. Shahi; Shrey K. Shahi Search for other works by this author on: GSW Google Scholar Jack W. Baker Jack W. Baker Search for other works by this author on: GSW Google Scholar Bulletin of the Seismological Society of America (2019) 109 (6): 2767. https://doi.org/10.1785/0120190236 Article history first online: 22 Oct 2019 Connected Content Errata: An Efficient Algorithm to Identify Strong‐Velocity Pulses in Multicomponent Ground Motions Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Shrey K. Shahi, Jack W. Baker; Erratum to An Efficient Algorithm to Identify Strong‐Velocity Pulses in Multi‐Component Ground Motions. Bulletin of the Seismological Society of America 2019;; 109 (6): 2767. doi: https://doi.org/10.1785/0120190236 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentBy SocietyBulletin of the Seismological Society of America Search Advanced Search An error in selecting the data used in the regression analysis by Shahi and Baker (2014) led to incorrect regression coefficients and model selection. With corrected data selection, the following are the correct results for the model. Table 1 should be corrected as follows: Parameters . Fault Type . Akaike Information Criterion (AIC) . R⁠, s Strike slip 265.03 R⁠, s Strike slip 263.32 R⁠, ln(s) Strike slip 264.33 R⁠, s⁠, θ Strike slip 261.02 R⁠, s⁠, θ Strike slip 261.73 R⁠... View Original Article You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Influence of multi-component ground motions on seismic responses of long-span transmission tower-line system: An experimental study

Seismic performance is particularly important for life-line structures, especially for long-span transmission tower line system subjected to multi-component ground motions. However, the influence of multi-component seismic loads and the coupling effect between supporting towers and transmission lines are not taken into consideration in the current seismic design specifications. In this research, shake table tests are conducted to investigate the performance of long-span transmission towerline system under multi-component seismic excitations. For reproducing the genuine structural responses, the reduced-scale experimental model of the prototype is designed and constructed based on the Buckingham\'s theorem. And three commonly used seismic records are selected as the input ground motions according to the site soil condition of supporting towers. In order to compare the experimental results, the dynamic responses of transmission tower-line system subjected to single-component and two-component ground motions are also studied using shake table tests. Furthermore, an empirical model is proposed to evaluate the acceleration and member stress responses of transmission tower-line system subjected to multi-component ground motions. The results demonstrate that the ground motions with multi-components can amplify the dynamic response of transmission tower-line system, and transmission lines have a significant influence on the structural response and should not be neglected in seismic analysis. The experimental results can provide a reference for the seismic design and analysis of long-span transmission tower-line system subjected to multi-component ground motions.

Frequency‐dependent principal component analysis of multicomponent earthquake ground motions

SummaryStochastic ground motion simulation techniques are becoming increasingly popular because of enhanced computation power enabling direct simulation of complex response quantities. Priestley process assumption is the most general approach for stochastic modeling of earthquake ground motion. However, a framework for multicomponent ground motion simulation using the general Priestley process assumption is not available. Multicomponent motions are useful especially when the correlation structure between them significantly influences the response. The present study proposes a framework for frequency‐dependent principal component analysis (PCA), which facilitates Priestley process–based simulation of multicomponent ground motions. The study focuses only on the frequency‐dependent PCA part, and the results show high dependency of the principal components/directions on the frequency bands of the signals. The present work also advocates that the frequency‐dependent PCA should be preferred to the conventional PCA as the former can address the issues related to the frequency‐independent uniform modulation associated with the latter.

An approach for synthesizing tri-component ground motions compatible with hazard-consistent target spectrum - Italian aseismic code application

A versatile approach for synthesizing non-stationary multicomponent ground motions compatible with a given target response spectrum is presented. In conjunction with performance-based structural design, the proposed approach combines a scenario-based procedure to select the target spectra of the three components of the motion, and a stochastic scheme, with an iterative wavelet-based method to generate the artificial time histories. In this context, the selection of an appropriate target spectrum is mandatory to synthesizing accelerograms with proper frequency content, input-energy, effective duration, and inelastic demand. In the scenario-based assessments, the target spectrum is derived directly from an earthquake scenario defined by seismic hazard disaggregation and strong ground-motion attenuation relationships. Firstly, the design spectrum specified by aseismic code provisions is replaced by a set of conditional mean spectra (CMS) for each of the ground motion components. Subsequently, an inverse stochastic dynamics problem, defined by a set of parametric evolutionary power spectra (EPS), is formulated and solved in a point-wise format for each CMS and for the three components of the motion. To improve the matching between the response spectrum of the simulated records and the CMS, an iterative procedure involving the family of harmonic wavelets is then employed. Post-processing for a proper baseline correction of the records is performed to synthesize ground-motions yielding realistic velocity and displacement traces. To illustrate the effectiveness of the approach, extensive numerical results pertaining to the Italian aseismic code provisions are included in this paper. In this regard, Monte Carlo simulations are undertaken to relate the CMSs to the evolutionary power spectrum. In particular, non-constant peak factor expressions via regression analysis are derived for various ground-motion durations. Finally, the nonlinear responses of elasto-plastic SDOF oscillators with different values of the yield strength reduction factor are considered. The oscillators subjected to artificially generated records and a set of natural unscaled and spectrum-compatible accelerograms, are examined in terms of ductility demand and equivalent number of yield cycles.

A general definition of integrated strong motion duration and its effect on seismic demands of concrete gravity dams

Various duration definitions have been proposed to describe the effective strong motion duration based on a single component of ground motions. However, multi-component accelerograms are usually selected as the seismic excitations to evaluate the seismic performance of important infrastructures. Duration definitions able to consider the duration contributions from all components of ground motions are still lacking. In this paper, a general integrated duration definition for multi-component seismic excitations is proposed based on the existing concept of strong motion duration. According to the proposed definition, integrated bracketed duration, integrated uniform duration, and integrated significant duration are presented to measure durations for multi-component ground motions. Twenty as-recorded accelerograms with a broad range of durations are considered to investigate the correlation between integrated and single component durations. A series of nonlinear dynamic analyses are performed to quantify the influence of different integrated ground motion durations on several seismic demands (i.e. peak displacement, damage dissipation energy, and local damage index) of concrete gravity dam-reservoir-foundation systems. In addition, the results also reveal the effects of vertical seismic excitations on the seismic response of concrete gravity dams and emphasize the necessity to consider vertical motions in seismic performance assessment of such infrastructures.

Seismic Responses of the Supporting Structure of FAST under Multiple-Support Excitations

Seismic ground motions are spatial incoherent partly due to uncertainty in fault mechanism and wave propagation. The spatial coherency and its effect can be important and need to be investigated for multiple-support structures. In this study, an investigation of seismic responses of a five-hundred-meter aperture spherical telescope (FAST) is investigated. The structure is a cable net structure with multiple supports. For the structural analysis, parameters of an existing coherency model for excitations along the same orientation but considering the multi-component excitations and spatially separated locations are developed using the records from Taiwan. This coherency model together with adopted target power spectral density function and phase difference spectrum model are used to simulate multi-component seismic ground motions at 338 grid points covering the FAST. The simulated records are used as the basis to interpolate the time history of the ground motions at 2395 supports for the considered structure. The time-history responses of the structure under incoherent multiple-support excitations are evaluated and compared to that under uniform excitations. The results show that the influence of coherency on the supporting structure of the FAST in three excitation directions differs. The analysis results show that as compared to uniform excitations, the consideration of the seismic coherency in seismic excitations leads to, on average, 87% of increase in stress for 94% of the main cables, and 22% of increase in stress for 44% of the tie-down cables. It was also noted that the maximum tensile stress of the cable by considering the coherency is 835 MPa while that under uniform excitations is 671 MPa. In both cases, they are smaller than the characteristic tensile strength of the cables used for design and construction of the FAST.

Estimating seismic demands for performance-based engineering of steel buildings

Author(s): Reyes, Juan Carlos | Advisor(s): Chopra, Anil K | Abstract: Earthquake engineering practice is increasingly using performance-based procedures for evaluating existing buildings and proposed designs of new buildings. Both nonlinear static and nonlinear response history analyses (RHA) are used for estimating engineering demand parameters (EDPs)--floor displacements, story drifts, internal forces, hinge rotation, etc--in performance-based engineering of buildings. Topics related to both analysis procedures are investigated in this dissertation.In the first part, the original modal pushover analysis (MPA) to estimate seismic demands due to one component of ground motion is extended to consider two horizontal components simultaneously in three-dimensional analysis of buildings, and to estimate internal forces and plastic hinge rotations directly from pushover analyses. Subsequently, the accuracy of MPA in estimating EDPs for tall buildings and unsymmetric-plan buildings is evaluated. Seismic demands for recently designed and built 48- and 62-story buildings with ductile concrete core walls--designed according to the alternative provisions of the 2001 San Francisco Building Code (SFBC)--due to an ensemble of 30 ground motions are computed by MPA and nonlinear RHA, and compared. We demonstrate that MPA procedure shows degree of accuracy that is sufficient for practical application in estimating median values of EDPs for tall buildings subjected to two horizontal components of ground motion. The accuracy of the extended MPA procedure is also evaluated for low- and medium-rise unsymmetric-plan buildings with ductile frames designed in accordance with the 1985 Uniform Building Code (UBC85) and the 2006 International Building Code (IBC06). Seismic demands are computed for six unsymmetric-plan buildings due to 39 ground motions acting simultaneously in two orthogonal horizontal directions. Comparing these results with those from nonlinear RHA, we demonstrate that MPA provides good estimates of EDPs whereas the procedures specified in the ASCE/SEI 41-06 standard and the Eurocode 8 are not satisfactory for estimating seismic demands for unsymmetric-plan buildings.The second part of the dissertation concerns nonlinear response history analysis of buildings. With the goal of developing effective procedures for selection and scaling of multi-component ground motions to be used in nonlinear RHA, a modal-pushover-based-scaling (MPS) procedure is developed in this investigation. The developed MPS procedure is an extension of the original MPS procedure for one component of ground motion to two horizontal components. In this investigation, each horizontal component of ground motion is scaled by a factor selected to match the deformation of its inelastic SDF system to a target inelastic deformation that may be estimated using a design (or response) spectrum. The properties of the inelastic SDF system are determined by pushover analysis of the building using the first-mode distribution. Based on the results for medium-rise symmetric-plan and unsymmetric-plan buildings with ductile frames, we demonstrate that the MPS procedure provides much superior results than the scaling procedure specified in the ASCE/SEI 7-05 standard.

An Efficient Algorithm to Identify Strong-Velocity Pulses in Multicomponent Ground Motions

Ground motions with strong velocity pulses are of special concern for structural engineers. We describe an efficient and quantitative method to identify such ground motions. Previous algorithms to classify these pulse-like ground motions con- sidered the ground motion in a single orientation, which made classifying pulses in arbitrary orientations difficult. We propose an algorithm that can identify pulses at arbitrary orientations in multicomponent ground motions, with little extra computa- tional cost relative to a single-orientation calculation. We use continuous wavelet transforms of two orthogonal components of the ground motion to identify the ori- entations most likely to contain a pulse. The wavelet transform results are then used to extract pulses from the selected orientations, and a new classification criterion based on support vector machines is proposed. Because we are mostly interested in forward directivity pulses, which are found early in the time history, a criterion to reject pulses arriving late in the time history is also proposed. The procedure was used to classify ground motions in the Next Generation Attenuation-West2 database (Ancheta et al., 2013). The list of pulse-like ground motions was then manually filtered using source- to-site geometry and site conditions to find the pulses most likely caused by directivity effects. Lists of both pulse-like ground motions and directivity ground motions are provided, along with the periods of the pulses and the orientations in which the pulses were strongest. Using the classification results, new models to predict the probability of a pulse and pulse period for a given future earthquake scenario are developed. Online Material: Table of all the pulse-like ground motions identified in the Next Generation Attenuation-West2 database, and HTML files of source-to-site geometry, the recorded time history, extracted pulse, and other directivity parameters for each identified pulse.

A parametric study of nonlinear seismic response analysis of transmission line structures.

A parametric study of nonlinear seismic response analysis of transmission line structures subjected to earthquake loading is studied in this paper. The transmission lines are modeled by cable element which accounts for the nonlinearity of the cable based on a real project. Nonuniform ground motions are generated using a stochastic approach based on random vibration analysis. The effects of multicomponent ground motions, correlations among multicomponent ground motions, wave travel, coherency loss, and local site on the responses of the cables are investigated using nonlinear time history analysis method, respectively. The results show the multicomponent seismic excitations should be considered, but the correlations among multicomponent ground motions could be neglected. The wave passage effect has a significant influence on the responses of the cables. The change of the degree of coherency loss has little influence on the response of the cables, but the responses of the cables are affected significantly by the effect of coherency loss. The responses of the cables change little with the degree of the difference of site condition changing. The effect of multicomponent ground motions, wave passage, coherency loss, and local site should be considered for the seismic design of the transmission line structures.

Correlations of three-component ground motions from the 23 June 2010 Val-des-Bois, Québec, earthquake

In this paper, we investigate the characteristics of three-component ground motions recorded during the \(M_\text{w}\,5.2\) Val-des-Bois (Quebec) earthquake, which occurred on the 23 June 2010. The earthquake is the largest recorded event in eastern Canada within the last decade. The records analyzed were provided by a strong motion monitoring network, comprising accelerometers located at sites with different soil conditions. The two orthogonal horizontal components and one vertical component at each recording station are uncorrelated to determine their principal directions, and the results obtained are used to characterize intensity ratios between the three uncorrelated components. A new hodograph representation is proposed to highlight the correlation between accelerations and displacement trajectories along various time increments at each recording station. The principal components are discussed in light of seismographic data, local site conditions, and trajectories. Time–frequency analyses of the uncorrelated records are also conducted to compare the distribution of spectral amplitudes and frequency content along the three principal components during the shaking. The results of this work shed more light on the characteristics of three-component ground motions from an important Eastern North America earthquake, and could be used to calibrate simulated multicomponent ground motions in this region.

Property of critical excitation for moment-resisting frames subjected to horizontal and vertical simultaneous ground motions

It has often been reported that, when building structures are subjected to near-fault earthquake ground motions, horizontal and vertical impulsive inputs may cause critical damage during the first few seconds. In practical design of building structures, however, the safety check, taking into account the effect of multi-component ground motions, is hardly conducted except the design of important structures such as high-rise buildings and nuclear power plants. Furthermore, it is not clear how the correlation of multi-component ground motions influences the actual safety of structures. In this paper, the detailed property of critical excitation is discussed in association with the relationship between the characteristics of ground motions and those of structures. The properties of various auto power spectral density (PSD) functions of the horizontal and vertical ground motions are investigated, and those of the critical cross PSD function of these two-directional ground motions are found by a devised algorithm in a feasible complex plane. A closed-form expression is derived from the critical relation of the auto PSD functions of the simultaneous inputs. This critical excitation method provides us with a new approach for earthquake-resistant design against the possible future earthquake which causes the critical damages to buildings.

Seismic behaviour of cable-stayed bridges under multi-component random ground motion

A frequency domain spectral analysis is presented for the seismic analysis of cable-stayed bridges for the multi-component stationary random ground motion incident at an angle with the longitudinal axis of the bridge. The ground motion is represented by its power spectral density function and a spatial correlation function. The analysis duly takes into account the spatial variation of ground motions between the supports, the modal correlation between different modes of vibration and the quasi-static excitation. Using the proposed method of analysis, an extensive parametric study is conducted to investigate the behaviour of the cable-stayed bridge under the seismic excitation. The parameters include the spatial correlation of ground motion, the angle of incidence of the earthquake, the ratio between the three components of the earthquake, the number and nature of modes considered in the analysis, the inertia ratio between the tower and the deck, and the nature of the power spectral density function of the ground motion.