Parametric Sensitivity of Ground Motion Pulse Filter for Response Control of Base-Isolated Buildings

Recently, the authors have proposed ground motion pulse filters for designing effective active and semi-active controllers for base-isolated structures subject to near-field earthquakes. The controller design is realized by augmenting the structural system equation with state-space model of the pulse filter. It has been observed that the resulting controllers are capable of simultaneously reducing peak values of base displacement, superstructure drift, and accelerations of the base and the superstructure simultaneously within practical range of control forces. Since the pulse model depends on ground pulse period, ground pulse decay factor, and the pulse shape factor, a parametric sensitivity analysis is carried out to find pulse parameters for a broad range of earthquakes. It is found that the performance of the controller doesn't vary significantly if the pulse period is underestimated by 50% or overestimated by 20% with respect to the actual ground pulse period, the ground decay factor is between 0.15 and 0.35 and the pulse shape factor is between 1 and 3.     

Evaluation of Strength Hierarchy of Beam-Column Joints of Existing RC Structures under Seismic Type Loading

To evaluate the strength hierarchy, three different types of exterior beam-column joint, i.e., gravity load designed, non ductile and ductile, following two different codes are considered. Strength of different components of beam-column joint, i.e., column, beam, and joint core, is individually calculated from different failure criteria. Shear strength of the joint is evaluated from softened strut and tie model. Strength hierarchy, ultimate strength, and critical failure modes of the specimens are analytically estimated and found to be well corroborated with the experimental results. The study will help in designing the earthquake resistant RC structures in a more rational way.     

The Variance of Collapse Capacity of Symmetric and Asymmetric Low-Rise RC-SMF Buildings

This study primarily investigates if the building asymmetry changes the variance of collapse capacity. The example models are five-story reinforced concrete buildings. The variance of collapse capacity is evaluated by first-order-second-moment method. There is a difference between the results of symmetric and asymmetric building models, independent of torsional behavior. The influence of record-to-record variability is more important than the effects of modeling uncertainty on the variance of collapse capacity. Plastic rotation capacity is the most important contributor to the variance of collapse capacity of high ductile buildings independent of the asymmetry.     

Effect of Cyclic Loading Frequency on the Behavior of External RC Beam-Column Connections

Reduced-scale external RC beam-column specimens with three typical deficiencies as beam weak in flexure (BWF), beam weak in shear (BWS) and column weak in shear (CWS) were tested under cyclic excitations of different frequencies, varying from 0.025–2.0 Hz. Parameters like load carrying capacity, stiffness degradation, energy dissipation, principal tensile stress were monitored for exploring the effect of rate of loading on different types of deficient beam-column connections in a holistic manner. Test results showed that the rate effect is significant in beam-column connection with BWF, while the same is not so significant in BWS and CWS specimens.     

INSTANTANEOUS OPTIMAL CONTROL FOR SEISMIC ANALYSIS OF NON-LINEAR STRUCTURES

In this paper, an effective active control algorithm is developed for the vibration control of non-linear structural systems subjected to earthquake excitation. It is an attempt to include the non-linear characteristics of the structural behaviour throughout the entire analysis (design and validation), accounting for the eventual cumulative structural damage and energy dissipation. This is a very important factor since, in current design practice, structures are assumed to behave nonlinearly when subjected to strong ground motion. The proposed algorithm focusses on the instantaneous optimal control approach for the development of the control algorithm where the nonlinearities are brought into the analysis through a non-linear state vector and a non-linear open loop term. A performance index that is quadratic in the control force and in the non-linear states and is subjected to a non-linear constraint equation, is minimised at every time step. The effectiveness of the proposed non-linear instantaneous optimal control (NIOC) strategy is critically evaluated in comparison with currently available active control techniques. Numerical simulation results indicate that the proposed approach provides a significant reduction of the peak response quantities, such as maximum response deformation, maximum response acceleration, ductility of the system, associated with a reduced maximum control force.     

THE ASSESSMENT OF TOTAL SEISMIC MOMENT

In this paper we address two problems: (a) the estimation of the total moment release for the calculation of average strain rates and (b) the assessment of the contribution to the total moment of earthquakes smaller than those available in regional or global catalogues. We also examine the bias associated with the different methods currently in use to estimate earthquake recurrence and total rate of seismic moment release, which are important considerations in engineering seismology and tectonics.     

Getting Started: Objectives and Justifications in the History of Neurology

Contemporary historiographical ideas have the potential to enrich the history written by practicing neurologists. Neurology is a science, and historians of neurology might profit from considering the experiences of historians of other sciences. An explicit consideration of the range of possible objectives, justifications, sources and methods of historical research may open new and exciting avenues of inquiry. Any plausible answer to the question, “What does a historian do when he or she sits down to write history” helps an historian to develop the structure of his or her project. The selection of sources for a historical study is improved, if also expanded, by understanding its aims.     

History of the Discovery of the Antipsychotic Dopamine D2 Receptor: A Basis for the Dopamine Hypothesis of Schizophrenia

The 1975 publication of Seeman et al. (Proc Nat Acad Sci, USA), reporting the discovery of the antipsychotic receptor in the brain, is a classic example of translational medicine research. In searching for a pathophysiological mechanism of psychosis, the team sought to identify sites that bound the antipsychotic drug haloperidol. Their criterion was that haloperidol bound to the site at one to two nanomoles per liter, corresponding to haloperidol concentrations found in spinal fluid or plasma water in treated patients. They requested de novo synthesis of tritiated haloperidol, and it readily detected specific haloperidol binding sites in brain striatum. With dopamine binding the haloperidol-labeled sites with higher potency than other neurotransmitters, the sites were named antipsychotic/dopamine receptors (now designated dopamine D2 receptors). Most significantly, they found that all antipsychotics bound these sites at concentrations and with a rank order of potencies that were directly related to the mean daily antipsychotic dose taken by patients with schizophrenia. Their findings enabled screening for new antipsychotics, initiated D2 receptor measurements in brain of living patients, and determination of minimum occupancy (65%) of D2 receptors for antipsychotic benefit. The collective work is generally viewed as providing a fundamental basis for the dopamine hypothesis of schizophrenia.     

The Iranian Chapter in the History of the Chuvash

The influence of the Iranian culture on Eastern Europe is undisputable. Scholars write of the Southern-Iranian road which stretched from the south, from the Parthians, Persia, and the Transcaucasia, to the north Iranian way through Khwarezm and as far as the Volga. The extent of the Iranian influence on the tribes populating southern Siberia prior to the Common Era however, is much less clear. It is believed that the Savirs/Suvars were the ancestors of the Chuvash. Although this theory has not yet been proven fully, it has served as a theme for historical and philological research. Drawing on geographic, religious, and linguistic materials this study attempts to trace the relationship between Iranian tribes and the Savir ancestors of the Chuvash.