Now showing 1 - 5 of 5
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    Vertical geometric irregularity in stepped building frames
    (01-08-2010)
    Sarkar, Pradip
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    Stepped building' frames, with vertical geometric irregularity, are now increasingly encountered in modern urban construction. This paper proposes a new method of quantifying irregularity in such building frames, accounting for dynamic characteristics (mass and stiffness). The proposed regularity index' provides a basis for assessing the degree of irregularities in a stepped building frame. This paper also proposes a modification of the code specified empirical formula for estimating fundamental period for regular frames, to estimate the fundamental time period of the stepped building frame. The proposed equation for fundamental time periods is expressed as a function of the regularity index. It has been validated for various types of stepped irregular frames. © 2010 Elsevier Ltd.
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    Estimation of short-term deflection in two-way RC slab
    (30-01-2009)
    Sarkar, Pradip
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    Govind, Maidhily
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    A study was conducted, to address the problem of estimating short-term deflections in reinforced concrete (RC) two-way slabs, using finite element analysis with appropriate stiffness modifiers. The study proposed a modified Branson's formulation, to account for the complex effects of flexural cracking and tension stiffening, along with a simple modification to account for torsional cracking. The parameters in proposed formulation are determined empirically and the procedure validated by 23 investigative loading-deflection data sets. The proposed formulation stated that the stiffness changes for an RC two-way slab, subjected to bi-directional bending and torsion throughout the slab. It was demonstrated that the stiffness changes throughout the slab, due to cracking, depending on the magnitude of the principal tensile stress. The study also demonstrated that the idea is, top retain the assumed isotropic behavior in the elasticity in the proposed approach.
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    Publication
    Seismic evaluation of RC stepped building frames using improved pushover analysis
    (01-04-2016)
    Sarkar, Pradip
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    Stepped building' frames, with vertical geometric irregularity, are now increasingly encountered in modern urban constructions. This paper proposes a new approach to determine the lateral load pattern, considering the contributions from the higher modes, suitable for pushover analysis of stepped buildings. Also, a modification to the displacement coefficient method of ASCE/SEI 41-13 is proposed, based on nonlinear time history analysis of 78 stepped frames. When the newly proposed load pattern is combined with the modified displacement coefficient method, the target displacement for the stepped building frame is found to match consistently the displacement demand given by the time history analysis.
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    Short-term deflections in two-way RC slabs using deflection coefficients
    (01-10-2008)
    Govind, Maidhily
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    Sarkar, Pradip
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    Estimation of deflections in RC slabs is important in the limit state design approach, as deflection control is often the governing condition for slab thickness. Unlike the case of one-way slabs, there is presently no simple procedure available in design codes as well as in the published literature to estimate maximum deflections of RC two-way slabs. The present study attempts to address this problem, with regard to estimation of short-term deflections in RC two-way slabs for which deflection coefficients are available. A modified Branson's formulation is proposed to assess the flexural rigidity of the two-way slab in order to account for the complex effects of cracking and tension stiffening. The empirical formulation is based on 16 experimental load-deflection data sets reported in literature for uniformly loaded rectangular panels on unyielding supports with simply supported and restrained edges.
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    Publication
    Design of RC beam-column joints under seismic loading - A review
    (01-02-2007)
    Sarkar, Pradip
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    Agrawal, Rajesh
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    A beam-column joint is a very critical element in reinforced concrete (RC) framed structure where the elements intersect in all three directions. Joints ensure continuity of a structure and transfer forces that are present at the ends of the members. The present provisions in IS 13920:1993 are inadequate, in terms of (i) minimum column width, (ii) column/beam flexure strength ratio, (iii) estimation of shear demand, (iv) assessment of shear strength, design and detailing of shear reinforcement, and needs to be upgraded regarding the beam-column joint under seismic loading. This paper reviews the design procedures for the RC beam-column joints under seismic loading reported in literature, with a special emphasis on three international codes of practice viz. ACI 318M-02, NZS 3101:1995 and prEN 1998-1:2003. It is pointed out that although there is a need for continuing research to resolve various disparities, there is an urgent need to revise IS 13920 suitably, in the interest of structural safety.