摘要:

AbstractWe present some numerical methods which simplify the analysis of equipment‐structure systems composed of an equipment component which is light with respect to the structure component. We consider completely general forms of equipment‐structure interaction. In particular, we consider that an arbitrary number of natural frequencies of the equipment and the structure are nearly equal (or equal) to each other.We show that this coincidence of natural frequencies implies that the equipment‐structure system will itself have several closely spaced natural frequencies. The essence of equipment‐structure interaction is the formation of beats, with slowly varying amplitude in each degree of freedom, between these natural frequencies‐at least in response to a δ‐function ground motion.We derive some differential equations, the solutions of which are a slowly varying envelope function (a vector) which yields the above slowly varying amplitudes. It is obtained by numerical integration using some conventional, but modified, methods and using a step size appropriate to capture its slowly varying nature.This envelope function defines the response to a δ‐function ground motion. We show how it may be combined with the properties of an arbitrary ground motion (acceleration record or response spectrum) to yield the response to such

ISSN:0098-8847    

DOI:10.1002/eqe.4290120502

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThis paper presents a method for determining the probabilities of fault displacement at specific locations on a fault of finite length. The method is further extended to include a procedure for estimating the maximum strain, stress and axial tensile force in a pipe crossing a fault. With this procedure, estimates are also obtained for the curved lengths of the pipe. The feasibility of the method is demonstrated through a specific example. For that purpose an X‐60 pipe crossing the San Andreas fault in Northern California is used. The procedure is particularly useful in risk consistent design and can be readily extended to structures other than underground pipe

ISSN:0098-8847    

DOI:10.1002/eqe.4290120503

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe behaviour of coupled lateral‐torsional systems subjected to seismic waves is investigated analytically. This paper present numerical results of a few case studies which show the contributions of each of the selected parameters to the rotational response of the structural systems. Dynamic eccentricity is used as an index to represent the level of the rotational response. Accidental eccentricities due to S‐H waves are evaluated. Design implications based on this study are also gi

ISSN:0098-8847    

DOI:10.1002/eqe.4290120504

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe Galerkin method of weighted residuals is used to determine the frequencies and associated mode shapes of asymmetric shear wall‐frame structures. The governing equations are formulated using the continuum approach by idealizing the structure as a shear‐flexure beam. Varying properties along the height of the building are considered. The effect of translational, rocking and torsional flexibilities of the foundation on the natural frequencies is also investigated. The method presented herein utilizes polynomial and transcendental displacement functions, and is found to be simple, versatile and effici

ISSN:0098-8847    

DOI:10.1002/eqe.4290120505

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe first known solution of the title problem is presented. The Ritz method is used, with algebraic polynomials forming the set of trial functions. The condition that all three components of displacement be zero at the four corners is straightforwardly enforced. Numerical studies show that the convergence is relatively slow, requiring more terms than for shells which are completely free. The class of problems studied includes independent, constant curvature in each of the directions parallel to the edges, yielding vibration modes which fall into one of four symmetry classes, with symmetry or antisymmetry of the displacements existing with respect to each of the two symmetry axes of the problem. Detailed results are given for the frequencies and mode shapes of the first two modes of each symmetry class for shells having square planform and circular cylindrical, spherical and hyperbolic paraboloidal curvatures. Accuracy of the results is partially established by comparison with other previously published, accurate results for the corner supported flat square plate.

ISSN:0098-8847    

DOI:10.1002/eqe.4290120506

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe available substructure method for the earthquake analysis of concrete gravity dams, including the dynamic effects of the impounded water and the flexible foundation rock, is extended to include the effects of alluvium and sediments invariably present at the bottom of actual reservoirs. Modelled approximately by a reservoir bottom that partially absorbs incident hydrodynamic pressure waves, these effects are incorporated into the continuum solution for the hydrodynamic pressure. The dam‐water‐foundation rock system is idealized as a two‐dimensional system and analysed under the assumption of linear behaviour.An example earthquake analysis is presented to demonstrate the results obtained from the analytical procedure. Computation times for several cases illustrate the efficiency of the analytical procedure. In particular, the additional computation time required to include reservoir bottom absorption is shown to be very

ISSN:0098-8847    

DOI:10.1002/eqe.4290120507

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractA base‐isolated building is liable to have a small horizontal eccentricity between the centre of mass of the superstructure and the centre of rigidity of the supporting bearings. In seismic analysis, the structure is modelled as a rigid block with tributary masses supported on massless elastomeric rubber bearings placed at a constant elevation below the centre of mass. This simplified system has three degrees of freedom: two translations and one rotation in the vertical plane.The investigation of the dynamic behaviour of a base‐isolated building is carried out for both the detuned and the perfectly tuned cases. In the detuned case, the natural frequencies of the system are assumed to be well separated. In the perfectly tuned case, the uncoupled rocking frequency is assumed to be identical to the vertical translational frequency, which may result from an unusual mass distribution and/or an extreme aspect ratio of the superstructure. Perturbation methods are implemented in finding the dynamic characteristics for both cases. However, the dynamic response of the perfectly tuned case is the major concern in this investigation.The Green's functions for the displacement response of the three‐degree‐of‐freedom system are derived for both the undamped and damped conditions. The response spectrum modal superposition method is used in estimating the maximum acceleration response. A simple method, accounting for the effect of closely spaced modes, is proposed for combining modal maxima and results in an approximate solution corresponding to a single‐degree‐of‐freedom system. This approximate solution may be used for the preliminary design of a base‐isolated structure.Numerical results for a base‐isolated building subjected to the vertical component of the El Centro earthquake of 1940 were carried out for comparison with these analytical results. The proposed modal combination method showed superiority over the conventional Square Root of the Sum of the Squares method in estimating maximum responses. The results also indicated that the approximate single‐degree‐of‐freedom system yields accurate estimations.It is shown that the effect of rocking coupling on the vertical response of base‐isolated structures subjected to transient loadings, such as earthquake motions, can generally be neglected as a result of the combined effects of the time lag between the maximum translational and rotational responses and the influence of damping in the isolation system, which for elastomeric bearings can be as high as 8

ISSN:0098-8847    

DOI:10.1002/eqe.4290120508

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe modal base forces in structures having a straight‐line mode of vibration are investigated. Making use of the orthogonality relationship between the different modes, a relation between the modal base shears and base moments is found in all but the straight‐line mode. This relation states that the contribution of the inertia forces to the modal overturning moments referred to the centre of rotation of the straight‐line mode is identically null. The contributions of the vertical forces and lateral constraints must, however, be accounted for. For the special case of the straight‐line mode being proportional to the height of each storey, the centre of rotation coincides with the base of the structure. For the case of the straight‐line mode being a uniform displacement, the centre of rotation is at infinity and the contribution of the inertia forces to the modal base shears identically disappears in all but the straight

ISSN:0098-8847    

DOI:10.1002/eqe.4290120509

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe energy approach using the variational procedure in conjunction with the finite difference technique has been applied for the Mindlin theory dynamic analysis of rectangular plates with cutouts in which account is taken of the effects of both transverse shear deformation and rotary inertia. This study has clearly demonstrated that the discrepancy with the thin plate theory solutions increases with increasing values of thickness ratio β and the error due to the thin plate assumptions increases particularly for the higher modes. It is also concluded that the effect of a cutout becomes more pronounced as the thickness of the plate approaches the size of cutout

ISSN:0098-8847    

DOI:10.1002/eqe.4290120510

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290120511

出版商:John Wiley&Sons, Ltd    

年代:1984

数据来源: WILEY