摘要:

AbstractThe moments of time to first passage of the response process of the linear oscillator excited by a stationary wide‐band process are obtained numerically for the symmetric two‐sided barrier problem. A recursive set of partial differential equations governing the moments is solved using a Petrov‐Galerkin finite element method. Stable, accurate solutions for the first few moments are calculated over a wide range of oscillator da

ISSN:0098-8847    

DOI:10.1002/eqe.4290090302

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractAn approximate method is proposed for the scattering of SH‐waves by foundations of irregular shape and the resulting soil‐structure interaction problems. The scattering of elastic waves by the rigid foundation embedded in half‐space is solved approximately by using integral representation of the wave equation. The procedure is the Born approximation which has been widely used in quantum mechanics for collision and scattering theory though not well‐known in elastodynamics. This paper extends the previous work of the authors on the scattering of waves to account for soil‐structure interaction. The motion of the foundation is evaluated by the balance of momentum under stresses due to the incident waves as well as the waves generated by its own motion and the forces coming from the superstructure. The model investigated consists of an infinitely long elastic shear wall of heightHand thicknessherected on a rigid infinitely long foundation. Results are presented for the cases with circular, elliptical and rectangular foundations. For a circular foundation, excellent agreement is found with the exact solutions for the foundation displacement and the relative displacement between the top and bottom of the structure for the entire range of wave numbers. For an elliptical foundation, accuracy decreases with increasing wave numbers. Foundation displacements are compared for foundation shapes that are shallow elliptical, deep elliptical, rectangular and circular. It is observed that foundation displacements are dependent on the angle of incidence except for a semi‐circle. The results on the details of the scattered field are, however, not

ISSN:0098-8847    

DOI:10.1002/eqe.4290090303

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractTorsional instability under harmonic excitation was detected in structures with cubic softening member stiffness. A variational procedure was introduced to perform the analysis for the general problem formulation. Single‐storey structures with zero eccentricity were studied first; previous findings were checked and corrected, and the behaviour was examined in greater detail. Two‐storey structures with large eccentricity were also examined, and further regions of torsional instability were detected. Time history analysis was then employed to quantify the behaviour of various typical structures. An unbounded growth in rotation or column displacement was not observed. Rather, the instability appeared to be related to the jump in response which exists in single degree‐of‐freedom softening oscillators subjected to harmonic excitation. The practical significance of torsional instability is therefore rather weak, although prudent practice would recommend its av

ISSN:0098-8847    

DOI:10.1002/eqe.4290090304

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractAn approximate method for the analysis of the dynamic interaction between a flexible rectangular foundation and the soil with consideration of the out‐of‐plane deformation of the foundation is presented. The procedure is based on an extension of the subdivision method developed by Wong and Luco for rigid foundations.Numerical results describing the influence of the flexibility of the foundation on the vertical and rocking impedance functions and on the contact stresses between the foundation and the soil are presented. The possibility of representing a flexible foundation by an equivalent rigid foundation having the same force‐displacement relationships is also discussed. The results obtained indicate that at low frequencies, the dynamic stiffness coefficients for flexible foundations are lower than those for a rigid foundation of the same area. At higher frequencies the opposite behaviour is observed. The radiation damping coefficients for flexible foundations are significantly lower than those for a rigid foundation of the same

ISSN:0098-8847    

DOI:10.1002/eqe.4290090305

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractOptimum parameters are determined for absorbers, which, when attached to one mass of a main system with two degrees of freedom, minimize the harmonic response of that mass. Comparison is made with the absorber parameters that are determined by treating the main system as an equivalent one degree‐of‐freedom system and using classical results. Close agreement is obtained if the ratio of the two natural frequencies of the main system is reasonably large. This is in agreement with the author's recent work on optimum absorber parameters which minimize the response of elastic bodies. The extension of the method to multi degree‐of‐freedom main systems is outlined. The conditions for which different values of these parameters are predicted when the response is minimized over narrow and broad frequency bands are det

ISSN:0098-8847    

DOI:10.1002/eqe.4290090306

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThis paper presents an approach to the problem of separation and sliding between soil and structure in the finite element analysis of dynamic soil‐structure interaction problems. Joint elements are arranged along the contact surface between soil and structure and they have a property such that tensile forces are not transmitted between the planes representing structure and soil in the finite element analysis. The dynamic properties governing the sliding are determined by the Mohr‐Coulomb failure law determined from the cohesion and the friction angle between soil and structure.The proposed method is applied to (i) a model of a reactor building resting on the free surface of layered ground and (ii) a buried foundation structure. The numerical computations reveal the following results: that the translation is dominant in the motion of the structure when sliding is taking place between soil and structure, and that the rocking is dominant in the rest of the response. The amplitude of the response during sliding is increased on any one point of the structure and decreased on any one point of the ground compared with that of the fixed condition at the interface. In the case of the buried structure, it is observed in the computed results that the structure and soil move in the opposite direction along the vertical contact surface and are separated from each other in the near surface region during the strong phase of the excitat

ISSN:0098-8847    

DOI:10.1002/eqe.4290090307

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractTwo‐dimensional analytical elastic models are developed for evaluating dynamic characteristics, namely natural frequencies and modes of vibration of a wide class of earth dams in a direction parallel to the dam axis. In these models the non‐homogeneity of the dam materials is taken into account by assuming a specific variation of the stiffness properties along the depth (due to the continuous increase in confining pressure). In addition, both shear and normal (axial) deformations are considered. Cases having constant elastic moduli, linear and trapezoidal variations of elastic moduli, and elastic moduli increasing as the one‐half, one‐third, two fifths, and a general (l/m)th powers of the depth are studied. Dynamic properties of three real earth dams in a seismically active area (Southern California) estimated from their earthquake records (input ground motion and crest response in the longitudinal direction) as well as results from full‐scale dynamic tests on one of these dams (including ambient and forced vibration tests) are compared with those from the suggested models. It was found that the models in which the shear modulus and the modulus of elasticity of the dam material vary along the depth are the most appropriate representations for predicting the dynamic characteristics. The agreement between the experimental and earthquake data and the theoretical results from some of the models is reason

ISSN:0098-8847    

DOI:10.1002/eqe.4290090308

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290090310

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290090311

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290090312

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY