摘要:

AbstractThe problem of determining optimal power spectral density models for earthquake excitation which satisfy constraints on total average power, zero crossing rate and which produce the highest response variance in a given linear system is considered. The solution to this problem is obtained using linear programming methods. The resulting solutions are shown to display a highly deterministic structure and, therefore, fail to capture the stochastic nature of the input. A modification to the definition of critical excitation is proposed which takes into account the entropy rate as a measure of uncertainty in the earthquake loads. The resulting problem is solved using calculus of variations and also within linear programming framework. Illustrative examples on specifying seismic inputs for a nuclear power plant and a tall earth dam are considered and the resulting solutions are shown to be realistic.

ISSN:0098-8847    

DOI:10.1002/eqe.4290241202

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractMaking use of a previously reported, simple, approximate method of analysis, a critical evaluation is made of the dynamic pressures and forces induced by horizontal ground shaking on a pair of infinitely long, parallel walls retaining a uniform viscoelastic solid. The walls are presumed to be rigid but elastically constrained against rotation at their base. The effects of both harmonic and earthquake‐induced excitations are examined. The accuracy of the method is assessed by comparing its predictions for the special case of fixed‐based walls with those obtained by an exact method, and comprehensive numerical data are presented which elucidate the underlying response mechanisms, and the effects and relative importance of the parameters involved. The parameters examined include the characteristics of the ground motion, the ratio of the distance between walls to the height of the contained material, and the flexibility of the rotational wall constraints. In addition to valuable insights into the responses of the systems investigated, the results presented provide a convenient framework for the analysis of more complex systems as w

ISSN:0098-8847    

DOI:10.1002/eqe.4290241203

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAn approximate method is presented for the analysis of earthquake induced uplifting in base plates of unanchored liquid‐storage tanks that are supported directly on flexible soil foundations. The method takes due account of the non‐linearities arising from the continuous variation of base contact area, membrane action and plastic yielding in the base plate. First, an ‘exact’ solution is presented for a uniformly loaded flexibly supported prismatic beam, uplifted by a concentrated force applied at one end. A series of such beams are later used in an approximate model of the base plate. The method is highly efficient and believed to be accurate for the level of uplifts encountered in practice. The results are presented for a range of foundation stiffness, representing loose sandy soils to rigid concrete mat. It is shown that, for the same overturning base moment, the flexibly supported tanks, in comparison with the rigidly supported tanks, experience significantly smaller axial compressive stress, but larger base uplift, foundation penetration, plastic rotation at plate boundary and hoop compressive stress in the ta

ISSN:0098-8847    

DOI:10.1002/eqe.4290241204

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe so‐called ‘strain‐rate effect’ in any material has been investigated here from a structural dynamics point of view. Starting with lumped‐mass models (SDOF and 2‐DOF) and assuming a rate‐independent failure criterion, it is shown here how a high loading rate produces an effect of strength enhancement in any massive elastic material and how failure takes place in a stronger component of a system as the loading rate increases. Extrapolating the concept of an equivalent elastic modulus as introduced in lumped‐mass models and extending the analysis to a semi‐infinite elastic continuum, an algorithm has been schematized to evaluate an overall equivalent elastic modulus of a concrete body under the influence of high loading rate treating the concrete as a two‐component solid mixture consisting of cement paste ma

ISSN:0098-8847    

DOI:10.1002/eqe.4290241205

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper presents a seismic design philosophy based on displacements rather than forces. By inverting the seismic design process, a rational method is established where member strength and stiffness depend on the target displacement. A comprehensive procedure for displacement‐based design of cantilever bridge columns is presented and verified by dynamic inelastic time history analysis. Parameter studies are used to examine the influence of several variables within the possible design solution spac

ISSN:0098-8847    

DOI:10.1002/eqe.4290241206

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractExperimental and analytical studies of base isolation by free rolling rods under basement are described in this paper. The tests of the system, a one‐storey, 326‐kg structure mounted on a set of free rolling rods, is carried out on a 3m× 3mshaking‐table. The dynamic behaviour of the isolated structure is studied and used to verify the analytical results. In the isolation system, the coefficient of kinetic rolling friction, measured at different angular velocities, ranges from 0·0007 to 0·0016. The coefficients are reduced by decreasing the angular velocities. Two earthquakes, a short‐period and a long‐period motion in Taiwan, are utilized as the input signals. The accelerations experienced by the superstructure are decreased by factors of 56 and 60 in comparison with the fixed‐base condition for the two input earthquakes. Also, for each test, the peak relative‐to‐ground displacement of the basement is nearly equal to the peak ground displacement, and the permanent displacement of the basement is present after the end of the earthquake. Finally, tests of the system with a recentring‐force device is undertaken, where a soft spring added to the basement reduces efficiently the permanent displacement. Comparisons show a good agreement between experimental and

ISSN:0098-8847    

DOI:10.1002/eqe.4290241207

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA procedure for three‐dimensional (3‐D) coupling of finite elements (FEs), boundary elements (BEs) and infinite boundary elements (IBEs) is presented for the numerical modelling of seismic interaction between arch dams and rock canyons. First, a system of coupling 3‐D boundary and infinite boundary elements is developed for simulation of infinite and irregular canyons and for determination, in the frequency domain, of impedance functions on the dam‐canyon interface. Secondly, the impedance functions for all degrees‐of‐freedom are transformed approximately into frequency independent discrete parameters by a curve fitting technique. Finally, these discrete parameters are combined with the dam structure which is discretized by finite elements, thus allowing the response of the arch dam‐canyon system to be evaluated. The proposed procedure is efficient because it permits the seismic analysis of arch dam‐canyon interaction by the substructure technique in the time domain. To demonstrate both the validity and efficiency of the present procedure, the response of an arch dam‐canyon system is obtained under unit impulse acting on the dam‐canyon interface as the free field input. Very good agreement is noted when comparing the frequency response determined from the time domain with that from the frequency domain under harmonic excitation applied on the interfac

ISSN:0098-8847    

DOI:10.1002/eqe.4290241208

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290241209

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290241210

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0098-8847    

DOI:10.1002/eqe.4290241201

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY