Cyclic Performance of an Elliptical-Shaped Damper with Shear Diaphragms in Chevron Braced Steel Frames

Several advantages of yielding dampers in controlling seismic energy have attracted the attention of many researchers in designing new buildings and retrofitting existing structures. In recent decades, various shapes and substances of such dampers have been used in engineering structures and their behavioral features, including the energy dissipating capacities, have been assessed. In this article, a novel method is presented to obtain the design relationship of two types of yielding elliptical dampers in terms of their selected geometric properties, i.e. distance between the shear diaphragms or virtual diameter and thickness. In addition, two different elliptical-shaped steel dampers equipped with the shear diaphragms are proposed and modeled using the finite element software ABAQUS and their performances are investigated. Then, 30 and 25 models, respectively, of the first and second types are studied using pushover analysis. The designed dampers considering the proposed relationships are used in two chevron braced steel frames placed between the bracing and the beam. Due to their desirable efficiency in energy dissipation and increase in the equivalent viscous damping of the frame, better efficiency is achieved in the modified damper with easier fabrication.     

Malaysia — democracy and the end of ethnic politics?

In this article I discuss Malaysia's turning point moments – the March 8^th General Election and the August 26th by-election which respectively saw the opposition's ascendancy and Anwar Ibrahim's political comeback. The opposition's ability to gain an ‘optimum multiethnic consensus’ had denied the incumbent of its unbroken two-thirds majority win. Its coalition arrangement was presented as a credible alternative to the 51 year-old winning but increasingly fractured coalition of the incumbent. In the final analysis a combination of a dwindling economy, the Abdullah-versus-Anwar leadership factor and the new media was what provided the major push for the swing. The article ends by posing various questions about the future of Malaysia's characteristic ethnic vote, the possibility of an emerging two-party system and of a probable Malaysia under Anwar Ibrahim.

     

Documentation of the Yazdi-Bandi Vault at the Plaza of Sadr-e-A’zam,Tehran

ABSTRACT

This article intends to document a previously unsighted sample of yazdi-bandi over an outlying structure in the old Bazaar fabric of Tehran, namely a plaza known as Timché-ye Sadre-A’zam. Recent renovations of the plaza have concealed the work under an austerely flat drop ceiling in gypsum. The old yazdi ceiling was only accidentally discovered by the authors following the trail of hearsay and local legends. The plaza is of late 19th century construction, a period that witnessed an evolutionary and aesthetic climax in all aspects of architectural geometry in the country, including the various branches of kaarbandi. With the limitations that the authors faced, basic tools were used in the scanning and surveillance of the ceiling. Photographs were collected using a wide-angle lens. They served as raw data for the reconstruction of the yazdi plan in AutoCAD, This article presents the findings, and for a better understanding of the entire premise by the reader, supplements them with preambles on the evolutionary history, geometrical analysis, a preview of the state of scholarship and a collection of relevant terms and concepts in the study of yazdi, in particular, and kaarbandi as a whole.