journal article
LitStream Collection
Home
BASU, B.; GUPTA, V. K.; KUNDU, D.
doi: 10.1002/(SICI)1096-9845(199612)25:12<1335::AID-EQE596>3.0.CO;2-Opmid: N/A
A theory based on Markovian principles and transition probability description is presented here to predict the statistics of the ordered peaks in a random process. It takes into account the statistical dependence that exists between the peaks in a single time history. The theory is more general than the other existing theories and, in special cases, it is shown to lead to the independent order statistics as well as to a first passage problem. Digital simulation has been carried out to validate the analytical results. The effects of governing parameters on the statistics of various orders of peaks have also been studied.
MONGKOL, J.; BHARTIA, B. K.; FUJINO, Y.
doi: 10.1002/(SICI)1096-9845(199612)25:12<1353::AID-EQE614>3.0.CO;2-2pmid: N/A
This paper proposes the Linear‐Saturation (LS) control as a new and suitable control algorithm for buildings with an Active Mass Damper (AMD) system. It takes into account the physical constraints on the AMD system and uncertainties in the loading. The LS control consists of a low‐gain linear control when the system is close to the zero state and bang‐bang control otherwise. This paper provides a precise formulation of the saturation control and presents optimal solutions which can be implemented in the state space. A numerical scheme to synthesize the switching surface which is needed to implement the bang‐bang control is developed. Furthermore, a method to demarcate the region for linear control is proposed. The effectiveness of the LS control is verified through numerical simulations with one‐ and multi‐storey buildings subjected to earthquakes. It is shown that the LS control provides better performance compared to even the gain‐scheduled LQ control.
doi: 10.1002/(SICI)1096-9845(199612)25:12<1373::AID-EQE615>3.0.CO;2-Ypmid: N/A
Tension‐Only Concentrically Braced Frames (TOCBF) exhibit deteriorating pinched hysteretic behaviour during strong earthquakes. Slender braces transit between an elastic buckling state, a restraightening state, in which they carry almost no load, an elastic tensile loading state as they are suddenly taut and, finally, a tensile yielding state. It has long been suspected that the sudden increase in tensile forces in the braces of TOCBSF creates detrimental impact loading on the connections and other structural elements. No experimental evidence, however, has been provided so far to confirm, or to quantify, this impact phenomenon. This paper addresses this issue through shake table tests of half scale, two‐storey, TOCBF models. By normalizing the hysteresis loops of braces obtained from shake table tests to the yield strength of steel obtained from quasi‐static tests, the increase in tensile forces in the braces was obtained. Results of dynamic tensile tests on steel coupons under similar strain rates as observed during the shake table tests showed that this increase in tensile forces is not the result of impact, but is rather caused by a yield strength increase of the steel under high strain rate. A procedure is proposed to estimate and account for this increase in tensile forces in the braces at the design stage.
doi: 10.1002/(SICI)1096-9845(199612)25:12<1391::AID-EQE617>3.0.CO;2-Wpmid: N/A
An indirect boundary integral equation method is used to investigate the scattering of elastic SH waves in a multilayered media with irregular interfaces. An extensive parametric error analysis is performed in order to assess the convergence of the proposed method. Subsequently, the numerical results for both steady‐state and transient surface response are given for one‐ and two‐layer models.
NAKAMURA, T.; TAKEWAKI, I.; ASAOKA, Y.
doi: 10.1002/(SICI)1096-9845(199612)25:12<1405::AID-EQE621>3.0.CO;2-6pmid: N/A
A shear building supported by a prescribed pile–soil system is subjected to bedrock earthquake input. A new design procedure is presented for generating a sequence of stiffness designs satisfying the constraints on interstorey drifts. The mean peak interstorey drifts of the shear building subjected to a set of spectrum‐compatible ground motions at the bedrock are evaluated by a modal combination rule. Tuning of the fundamental natural period of a shear building with a fixed base with that of a shear beam ground results in a non‐monotonic sequence of stiffness designs with respect to a ground stiffness parameter and previous approaches cannot be applied to such a problem. This difficulty in finding such a non‐monotonic sequence is overcome by utilizing the ground stiffness parameter and the superstructure stiffness parameter alternately in multiple design phases and by developing a new multi‐phase perturbation technique. Fundamental characteristics of this sequence of stiffness designs and the effect of ground stiffnesses on the design of the shear building are disclosed. It is further shown that the stiffness contour method is also useful for the design procedure such that a scattering effect in the estimates of ground stiffnesses is taken into account. The usefulness of the proposed procedure of sequential stiffness design and contour line method is demonstrated through several sequential design examples.
doi: 10.1002/(SICI)1096-9845(199612)25:12<1421::AID-EQE628>3.0.CO;2-Wpmid: N/A
Insight into radiation damping of an unbounded medium is developed by addressing the relative contributions of the elastic restoring force and the inertial force at infinity. When the inertial force dominates, radiation damping occurs. When the elastic restoring force dominates, no radiation damping arises. An unbounded medium with a cutoff frequency can also be identified.
COLLINS, K. R.; WEN, Y.‐K.; FOUTCH, D. A.
doi: 10.1002/(SICI)1096-9845(199612)25:12<1433::AID-EQE629>3.0.CO;2-Mpmid: N/A
The seismic design provisions of most building codes in the United States specify ground motion parameters for various regions of the country and provide simple formulae to determine a distribution of lateral forces for which the structure should be designed. Although the code provisions are very simple to use, they oversimplify a complex problem and are based on many implicit assumptions which many designers may not appreciate. Furthermore, the reliability of the final design is not easily determined. This paper describes a reliability‐based seismic design procedure for building structures. It is a performance‐based design procedure which requires the designer to verify that a particular structural design satisfies displacement‐based performance criteria. An equivalent system methodology and uniform hazard spectra are used to evaluate structural performance. The performance criteria are expressed in probabilistic terms, and deterministic design‐checking equations are derived from these criteria. The design‐checking equations incorporate design factors (analogous to load and resistance factors) which account for the uncertainty in the seismic hazard, the uncertainty in predicting site soil effects, and the approximate nature of the simplified models of the structure. The alternative procedure should enable designers to achieve code‐specified target performance objectives for moderate and severe levels of earthquake excitation.
Showing 1 to 10 of 10 Articles