Use of recycled concrete aggregates in sustainable structural concrete applications

The increasing difficulty in securing natural coarse and fine aggregates for the production of concrete coupled with the environmental issues and social costs of unlimited extraction of natural aggregates makes the usage of recycled aggregate concrete (RCA) in the construction industry of prime importance. However the full use of the material can be justified only through structural applications. Engineers are reluctant to use RCA in structural applications due to lack of design information. A brief review of the recent literature on Recycled Aggregate Concrete (RCA) used as a structural material is reported in this paper. It is found that the most of the research studies conducted up to now are mostly based on material properties rather than investigation of the RCA and its performance as a structural material. Major issues and problems associated with RCA concrete compared to normal concrete are identified in the paper

Soil Amplification in Low-to-Moderate Seismic Regions

The results of a study that investigates potential revisions of the spectral shape factors used in standards in regions of low-to-moderate seismicity are presented here. Using an equivalent linear analysis, the investigation particularly focuses on the effects of seismic intensity associated with rare and very rare intraplate earthquake events on site response. The Pacific Earthquake Engineering Research Center ground motion database (PEER) is used in selecting appropriate acceleration-time histories for the intraplate region. The results are normalised for comparison with the current spectral shape factors given in the Australian Standards for Earthquake Actions AS 1170.4:2007, with some differences being observed. The dependency of site amplification on seismic intensity was only observed for soil classes Ce, De and Ee. The rock site of class Be had considerably higher response in the short period range relative to class Ee. The records from the PEER ground motion database were also used for comparison with the results from this study, using a modified normalisation approach. The results from this study correlate well with the records from PEER

Displacement-controlled behavior of asymmetrical single-story building models

Displacement controlled behavior is a feature of low to moderate seismicity areas where the peak displacement demand on structures could be limited despite significant structural strength and stiffness degradation. In this article, the extension of the displacement controlled phenomenon to torsionally unbalanced framing systems is investigated. It is shown that the displacement demand of critical elements within a building can be insensitive to changes in eccentricity and torsional stiffness properties. While torsional actions is a well-researched topic, the incorporation of displacement controlled phenomenon into the analysis is original and represents a new development