摘要:

AbstractIn order to extend our knowledge of the performance of long‐span bridges under earthquake loading the effects of spatial variability of ground motion on the structural response of cable‐stayed bridges are studied; the result can be useful to practising bridge engineers. The multiple‐support excitation analysis is described, and two three‐dimensional models representing the modern and future trends in cable‐stayed bridge design are utilized to shed some light on salient features of the seismic response characteristics of these modern bridges. In addition, models of steel‐ and concrete‐design alternates of an existing bridge are considered. Differential ground motion records (obtained from dense instrument arrays) are used as synchronous and non‐synchronous support motions; in addition, non‐dispersive seismic waves travelling along the bridge are considered. The bridge response to non‐uniform ground motion is compared to its response to uniform input. An overview of the unique dynamic characteristics of these cable‐supported bridges is also presented. Finally, the study, which was used in the seismic design of several existing cable‐stayed bridges in U.S. and Canada, indicates that the response quantities may increase substantially from the non‐uniform input ground motion, especially for more rigid bridges and for bridges having different dynamic properties of the local soils at the supporting points, but the degree of increase depends upon the specific problem, in particular upon the aspects of span length, rigidity and structural redundancy. Thus, the response to non‐uniform input ground motion should be

ISSN:0098-8847    

DOI:10.1002/eqe.4290210101

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe equations of motion of a rotor finite element subjected to six components of base excitation are developed by applying variational principles. The equations contain speed dependent gyroscopic terms, base rotation dependent parametric terms and several forcing function terms which depend upon the linear accelerations, rotational accelerations and a combination of linear and rotational velocities. To evaluate the importance of various terms, seismic response characteristics of a rotating machine subjected to simulated base excitations are studied. It is observed that even for strong rotational inputs the parametric terms in the equation of motion can be ignored without affecting the response. The rotational input terms in the forcing function, however, are quite important and can be ignored only when they are not very strong. Since the problematic parametric terms can be ignored, one can use a generalied modal analysis approach.

ISSN:0098-8847    

DOI:10.1002/eqe.4290210102

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractOver 700 accelerograms recorded from 12 earthquakes in northeast Taiwan have been analysed for investigating the behaviour of the vertical and horizontal peak and spectral ground motion in the near‐source region. Pseudo‐relative spectral velocities (PSV), at 5 per cent critical damping for 23 frequencies in the range of engineering interest have been subjected to non‐linear regression procedures in terms of magnitude and hypocentral distance. Predicted response spectra for several discrete distances and magnitudes are presented. The results show that the shape of response spectra for both vertical and horizontal components of ground motion is magnitude‐ as well as distance‐dependent.The 2/3 ratio of vertical to horizontal ground motion, commonly used in engineering applications, appearsunconservativein the very near field for high frequency ground motion. However, it falls below 1/2 at distances greater than 50 km. The same ratio for peak ground velocity (PGV) and peak ground displacement (PGD) tends to increase with distance—the latter at a

ISSN:0098-8847    

DOI:10.1002/eqe.4290210103

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractAn efficient time truncation algorithm for transient two‐dimensional wave propagation analysis by the boundary element method is proposed. First the complete (without any truncation) formulation is reviewed and subsequently time truncation concepts are discussed. Three applications are presented, where the efficiency ofcomplete and truncated algorithmsis compared. The most important conclusions inferred from the numerical analyses are: (i)time truncation errorscan be controlled and made as small as required and (ii)time truncation algorithmslead to considerable savings in both CPU time and storage are

ISSN:0098-8847    

DOI:10.1002/eqe.4290210104

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA local transmitting boundary is presented in a compact form, which can be directly incorporated into finite elements. The accuracy of the boundary is studied thoroughly for a one‐dimensional model in order to clarify numerical instabilities introduced by the boundary. Discretization of the model and reflection from the boundary are rigorously considered in the study, and the mechanism of the instability is then illuminated in the frequency domain by the amplification of reflection from the boundary and the multi‐reflection of wave motion in a finite computational region. Typical characteristics of the instability in the time domain are illustrated by numerical results of the simple model and explained completely by the mechanism. On the basis of this understanding of the mechanism, a modified transmitting boundary is devised and its stability criterion is given for the one‐dimensional

ISSN:0098-8847    

DOI:10.1002/eqe.4290210105

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper presents a study for the development of a system capable of performing real‐time pseudo dynamic testing. The system combines the basics of the pseudo dynamic test with a dynamic actuator, a digital displacement transducer and a digital servo‐mechanism. The digital servo‐mechanism has been introduced to ensure accurate displacement and velocity control, in which digital feedback control with a time interval of 2 msec has been performed continuously during actuator motion. Using the system, pseudo dynamic tests under sinusoidal and earthquake ground motion are carried out for a structure having a viscous damper, demonstrating that a perfectly real‐time pseudo dynamic test can be achieved by incorporating the modified central difference method into an extra buffer operation of the digital servo‐mechanism. The responses solved by the pseudo dynamic tests are compared with the responses of the test structure as well as those obtained from post‐numerical analysis, and it is found that the real‐time pseudo dynamic test conducted in this stud

ISSN:0098-8847    

DOI:10.1002/eqe.4290210106

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290210107

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290210108

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY