摘要:

AbstractA comprehensive analysis is made of the harmonic response of vertically excited, massless, rigid ring foundations supported at the surface of an homogeneous elastic halfspace. The parameters considered include the thickness to radius ratio for the ring, the frequency of the exciting force and of the resulting steady‐state response, and Poisson's ratio for the supporting medium. The response quantities examined include the stiffness and damping coefficients of the system in an equivalent spring–dashpot representation of the supporting medium, the displacements of the foundation and of points on the ground surface away from the foundation, and the normal pressure at the foundation–medium interface. The results in each case are compared with those obtained for a solid disk having the same radius as the outer radius of the ring, and a simple approximate model is used to interpret the results and to provide insight into the action of the system. The reported data are computed by a method of analysis that takes due account of the mixed boundary conditions at the surface of the halfspace, and are believed to be of high acc

ISSN:0098-8847    

DOI:10.1002/eqe.4290150102

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractExperimental studies have been carried out on the dynamic stability of a cantilever cylindrical shell partially filled with liquid, under vertical excitation. Two polyester test cylinders with radius 100 mm, thickness 0.25 mm, and lengths 113 and 227 mm were used. The test cylinder was harmonically excited with constant acceleration‐ or displacement‐amplitude. It was found that not only the parametric principal instability resonance but also the parametric combination involving two natural vibrations, each of which has the same circumferential wave number but different axial mode numbers, could occur. The latter type of vibration apparently has not been previously studied. By varying the dimensionless water height from 0.25 to 1.0 stepwise by 0.25 increments, the instability regions and vibration modes were determined for the two test cylinders. The response waves of shell wall and liquid free surface, and axial and circumferential vibration modes were also obser

ISSN:0098-8847    

DOI:10.1002/eqe.4290150103

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractTheoretical analyses are presented for the dynamic stability of a clamped‐free cylindrical shell partially filled with liquid, under vertical excitation. In the analyses, the dynamic version of the Donnell equations and the velocity potential theory were used for the motions of the shell and the liquid, respectively. The problem was solved by using the modified Galerkin method so as to satisfy the boundary conditions. The equations of motion coupling the shell and the liquid were derived from a type of coupled Mathieu's equation. It is found that the parametric principal resonance could occur, as well as the parametric combination resonance of the sum type, involving two natural vibrations with the same circumferential wave number but with different axial mode number. The latter type of parametric resonance apparently has not been previously studied. The instability regions where parametric resonance occurs were determined by using Hsu's method.17To compare with the experimental results which had been stated in a companion paper,15detailed numerical calculations were carried out for the two test cylinders partially filled with water. Excellent agreement between theory and experiment was demonstrated for the instability region

ISSN:0098-8847    

DOI:10.1002/eqe.4290150104

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractA response spectrum procedure is developed for seismic analysis of multiply supported secondary systems. The formulation is based on the random vibration analysis of structural systems subjected to correlated inputs applied at several supports. For a proper response spectrum analysis of a multiple support system, the support inputs are required to be defined in terms of the auto and cross pseudo‐acceleration and relative velocity floor response spectra. Also information about the floor displacements and velocities as well as their correlations is required. The response of the secondary system is expressed as a combination of the dynamic and pseudo‐static response components. The dynamic component is associated with the inertial effects of the support accelerations, whereas the pseudo‐static component is due to the displacement of the supports relative to each other. Herein, the correlation between these two parts of the response is included through a term called the cross response component. Each of these components of the response can be calculated by a response spectrum method. The application of the proposed method is demonstrated by numerical exa

ISSN:0098-8847    

DOI:10.1002/eqe.4290150105

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractFor proper seismic analysis of secondary systems with multiple supports, the prescription of the seismic input in terms of the conventional pseudo‐acceleration floor response spectra is quite inadequate. It is necessary that the relative velocity floor response spectra as well as the cross floor response spectra, characterizing the correlation between the motions of various floors where the secondary system is attached, be also prescribed as the inputs. In addition to these, it is also necessary to define the floor displacements, velocities and their correlations. In this paper, the methods which can use the ground response spectra directly to obtain these inputs are developed. These methods are based on the random vibration analysis of the supporting primary structure, but still do not require the base input in stochastic form; conventional ground response spectra can be directly used. Numerical results demonstrating the application of the approaches are give

ISSN:0098-8847    

DOI:10.1002/eqe.4290150106

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThis paper presents a procedure for computing inelastic design spectra in terms of yield displacement. The procedure results in substantial computational savings as compared to the current procedures for computing the inelastic spectra in terms of displacement ductility. The proposed method is used to obtain inelastic design spectra for alluvium and rock. The results for alluvium are compared to those from the Newmark and Hall,10Riddell and Newmark12and Lai and Biggs4studies. The findings indicate that for given ductility and frequency one may de‐amplify the elastic response or reduce the elastic forces more for a structure on rock than for a structure on alluvium.A technique is presented so that the inelastic design spectrum can be scaled to any desired yield displacement and acceleration. An example is presented to illustrate how the proposed inelastic spectra can be used to compute the required ductility for a given syste

ISSN:0098-8847    

DOI:10.1002/eqe.4290150107

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractAn alternative technique to obtain the dynamic response of a massless rigid circular foundation resting on a uniform elastic half‐space when subjected to harmonic plane waves is presented. The technique relies on the use of an integral representation involving the free‐field ground motion and the contact tractions obtained in the course of calculating the dynamic force–displacement relationship of the foundation for external forces. Tables listing the translational and rotational components of the response of the foundation for non‐vertically incident SH, P, SV and Rayleigh waves are pr

ISSN:0098-8847    

DOI:10.1002/eqe.4290150108

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractFrom the past studies of acceleration records, it is generally recognised that peak acceleration is not a suitable measure of the ground motion for design purposes. Usually, peak accelerations are difficult to predict. They occur in high frequency pulses containing very little energy and therefore are of little consequence. On the other hand acceleration has direct and useful application in engineering design.A new parameterA95is introduced in this paper which is defined as that level of acceleration which contains up to 95 per cent of the Arias Intensity. From the study of 135 records, it is noticed that the variation of the fraction of Arias Intensity with acceleration level can be described by a very well defined relationship. It is also observed thatA95and Arias Intensity bear a stable relationship. Furthermore, the Arias Intensity at a site correlates more closely with the earthquake magnitude and the distance of the site from the source in attenuation relationships. From the available data, relationships are derived which show that there is a difference between the near‐field and the far‐field attenuation laws.The following relationships are obtained:whereEs= Arias Intensity,Ex= fraction of Arias Intensity above an acceleration levelA, M= surface wave magnitude,R= nearest distance to the energy source or focal distance in

ISSN:0098-8847    

DOI:10.1002/eqe.4290150109

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThis paper gives exact Bernoulli–Euler dynamic flexural member equations for a uniform beam on an elastic foundation. These enable exact results to be obtained when the beam is included in free or sinusoidally forced vibration calculations for a plane or space frame, at any frequency. In addition, information is presented to ensure that no natural frequencies are missed in a free vibration analysi

ISSN:0098-8847    

DOI:10.1002/eqe.4290150110

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290150111

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY