Kolkata, India
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Chakroborty S.,SMS India Pvt. | Roy R.,Bengal Engineering and Science University
Journal of Architectural Engineering | Year: 2016

There is no general consensus among researchers for selecting appropriate set of ground motions for the evaluation of inelastic seismic response of plan-asymmetric structures. In this backdrop, the role of important ground motion characteristics on the demand of a plan-asymmetric system is studied by using a number of records with widely varying characteristics but adjusted (using wavelets) to a common spectral shape. An equivalent single-story rigid-diaphragm model with simple elastoplastic hysteresis behavior is employed. Efficient strength design, viz, center of strength-center of mass (CV-CM)-coinciding strategy, is adopted in recognition of the strength-dependent stiffness characteristics of the load-resisting elements. It has been shown that the torsion-induced response of such systems is statistically insensitive to important ground motion parameters such as duration, frequency content, the interrelationship between two horizontal components, and the energetic length scale. Conversely, this study shows that a remarkable correlation exists between the carefully selected ground motion parameters and overall seismic demand as a result of coupled lateral-torsional vibration. The results motivated the authors to conceptualize a master curve that offers an a priori estimate of inelastic seismic demand of asymmetric systems when two widely used ground motion parameters, viz, peak ground acceleration (PGA) and mean period (Tm), are known. Thus, this study provides a background for dispelling the long-held controversy regarding the selection of an appropriate ground motion suite for assessing torsional response. © 2016 American Society of Civil Engineers.

Roy R.,Bengal Engineering and Science University | Chakroborty S.,SMS India Pvt. Ltd.
Journal of Earthquake Engineering and Engineering Vibration | Year: 2013

View of the recognition of the importance of the interdependent behavior of strength and stiffness of walltype structural elements, the seismic demand of plan-asymmetric systems is revisited. Useful strength distribution strategies, i.e., 'Center of Strength-Center of Mass (CV-CM) coinciding' and 'Balanced Center of Strength-Center of Resistance (CV-CR)' are adopted. Design charts for the seismic demand of classical uni-directionally and bi-directionally asymmetric systems are developed in a simple unified format. A conceptual framework is also outlined to conveniently apply the design charts. Illustrations are included to explain the use of the current recommendations in practical design. The study also highlights the relative performance of 'CV-CM coinciding' and 'Balanced CV-CR' criteria.

Roy R.,Bengal Engineering and Science University | Thakur P.,Bengal Engineering and Science University | Chakroborty S.,SMS India Pvt
Soil Dynamics and Earthquake Engineering | Year: 2014

Ground motions are often scaled to certain convenient target spectra in the response assessment of structures. While uniform hazard spectrum (UHS) is more widely used, conditional mean spectrum (CMS) is recently proposed as a more desirable target for scaling of real accelerograms. In this backdrop, the present study spectrally scales, using wavelets, a set of near-field and far-field ground motions to both the targets, viz., UHS and CMS. Relevance of a set of useful ground motion characteristics, viz., the peak ground acceleration-to-peak velocity ratio (amax/vmax), predominant period (Tp), Arias intensity (Ia), Housner intensity (IH), cumulative absolute velocity (CAV) and significant duration (Td *), is reviewed. Influence of ground motion scaling is discussed in terms of possible changes of such identified parameters. Seismic demand of horizontally irregular structures is assessed under both scaled and seed records recognizing strength dependent stiffness. Threshold of the scale factor, shown to have well-correlated with the change of ground motion characteristics, may be as high as ~10 to adequately estimate torsion-induced amplification in asymmetric system without any bias. © 2013 Elsevier Ltd.

Hofmann A.,SMS Siemag AG | Reichel J.,SMS Siemag AG | Loginov S.,SMS Siemag AG | Das S.,SMS India Pvt. Ltd.
Stahl und Eisen | Year: 2012

Inexact operating conditions are frequently the limiting factor in process models for steelmaking plants. To minimize the problems, SMS Siemag AG has examined the effects which operating conditions such as errors in the hot metal weight and in hot metal analysis have on the result of the BOF model at the end of blowing and conducted tests in several steelmaking plants. Special emphasis was put on a novel corrective calculation in order to improve the results despite adverse conditions. This corrective calculation is based on a sublance measurement and on the evaluation of the waste-gas analysis during the dynamic phase. The desired aims in terms of carbon and temperature could thus be achieved even under suboptimal conditions.

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