Utilization of lime for stabilizing soft clay soil of high organic content

This paper presents the results of geotechnical and mineralogical investigations on lime-treated soft clay soil from Idku City, Egypt, where high organic matters of about 14% exist. Lime was added in the order of 1, 3, 5 and 7% by weight and laboratory experiments after 7, 15, 30 and 60 days were conducted including the mineralogical and microstructural examinations, grain size analysis, plasticity limits, unconfined compressive tests, vane shear tests and oedometer tests. The results indicate that soft clay soil of high organic content of 14% can be stabilized satisfactorily with the addition of 7% lime. The results also demonstrate that the changes in the mineralogical contents and soil fabric of high organic lime-treated soft clay improve soil plasticity, strength and compressibility

Seismic performance evaluation of deficient steel moment-resisting frames retrofitted by vertical link elements

In many earthquake prone regions in developing countries, substandard steel moment resisting frame (SMRF) systems pose a profound danger to people and economy in the case of a strong seismic event. Eccentric bracing systems with replaceable vertical links can be utilized as an efficient and practical seismic retrofitting technique to reduce future earthquake damages to such structures. This paper aims, for the first time, to demonstrate the efficiency of eccentric bracing systems with vertical links as a seismic retrofitting technique for the SMRF structures with WCSB and to develop fragility curves for such structures. To achieve this aim, first, the effect of the vertical links on the behaviour of 3, 5 and 7-storey frames are studied through conducting the Nonlinear Static Analyses (NSA) as well as Nonlinear Time History Analyses (NTHA) using the artificial accelerograms compatible with the target design spectrum. The analysis results indicate that, as aimed in the design stage, the seismic damage is only concentrated at the replaceable vertical links and remaining structural members work mainly in the elastic range. In addition, the proposed retrofitting technique considerably improves the performance of the deficient SMRF systems by effectively restricting the displacement response and damage distribution in such structures. Following the NTHA, Incremental Dynamic Analyses (IDA) are performed to develop the seismic fragility curves for the retrofitted SMRF systems. The results indicate that the proposed retrofitting technique significantly reduces the fragility of such systems, and therefore, can provide a simple and efficient method to improve the seismic performance of deficient steel moment resisting frames in seismic regions

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