Book reviews

The Cambridge History of Iran, Volume I, The Land of Iran. Edited by W. B. Fisher. Cambridge: Cambridge University Press, 1968. xix + 784 pp., maps, bibliogr., index. $12.50.

The Cambridge History of Iran. Volume V, The Saljug and Mongol Periods. Edited by J. A. Boyle, Cambirdge: Cambridge University Press, 1968. xiii + 763 pp., maps, tables, bibliog., index. $12.50.

Planning and Development in Iran. By George B. Baldwin. Baltimore, Maryland: The Johns Hopkins Press, 1967. xv + 212. $6.95.     

Increasing Seismic Energy Dissipation of Steel Moment Frames Using Reduced Web Section (RWS) Connection

Connections of steel moment frames are vulnerable to brittle failure. Providing a perforation near the beam-ends is suggested as a potential method to improve seismic behavior of these structures. This article presents a numerical study on the energy dissipation of steel moment connections with perforated beam. Models with elongated circular openings of different dimensions and location are analyzed and compared based on the global and local damage indices, predicted failure time and dissipated energy. Results show that an RWS connection with a proper opening size can develop reasonable inelastic deformations and provide an acceptable seismic improvement to moment-resisting frames.     

Urban Air Pollution in Iran

Urban air pollution is a major health risk in several large Iranian cities. Transportation, extensive use of fossil fuels, outdated urban fleets of gasoline and diesel vehicles, industrial sources within and close to the city boundaries and natural dust are major contributing factors. Starting with Tehran, emission inventories and mathematical air pollution models are being developed. Air quality is being monitored and reported to the public, though data availability and validity remain a challenge. While national and local air pollution mitigation plans are in place, progress remains slow, coordination is weak, and sources of funding are limited.     

Natural Frequency of Single Pier Bridges Considering Soil-Structure Interaction

Because of the crucial role of free vibration frequency of a structure (e.g., a bridge) in design procedure, more realistic estimation of the frequency ends up in safer and more optimized design. As obtaining the free vibration frequencies of a bridge, considering soil-pile group-structure interaction, provide more realistic values, development of an analytical model to obtain such free vibration frequencies is studied in this research work. Most researchers have studied models with a single pile foundation. The purpose of this study is to assess soil-structure interaction (SSI) effects on dynamic performance of pile group supported bridges. A new analytical model is proposed to predict seismic analysis of these bridges. Applying the dynamic equations of motion for the system, SSI effects have been estimated. Based on the suggested analytical model, a new approximate equation is proposed for calculating natural frequency of pile group supported bridges. Equation accuracy has been investigated by comparing the results with those achieved by previous studies. Most periods calculated by the approximate equation are similar to those given for other case studies, indicating that the model could be applicable to other projects. Since the proposed model is very similar to real soil-pile-pier systems, this approximate equation can be used in preliminary seismic design of bridges.