Now showing 1 - 10 of 10
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    Lateral load behaviour of squat RC structural walls
    (01-02-2014)
    Mondal, Kaushik
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    Jaiswal, Arvind Kumar
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    Structural walls are important component of buildings, which have a high lateral load resisting capacity. These walls increase lateral stiffness of whole structure and reduce the lateral deflection. In low rise buildings, structural walls prevent the collapse of structure during strong earthquakes. Squat RC structural walls resist lateral forces through strut and tie action. An analytical study is carried out to understand lateral load behaviour of squat walls for various aspect ratios of squat walls and wall reinforcement ratios; the diagonal strut width and strut angle are assessed, which are crucial inputs in design of squat walls based on strut & tie approach. The results of nonlinear analyses suggest that strut & tie modelling is possible to design squat walls, because there is an orderly behaviour of walls even at large diagonal angle of wall and therefore of the strut angles. Existing code provisions are compared and new provisions to be included in the Indian codes are suggested.
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    Expended energy based damage assessment of RC bare frame using nonlinear pushover analysis
    (01-10-2017)
    Vimala, A.
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    Kumar, R. Pradeep
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    A fresh damage approach is proposed for quantitatively estimating seismic damage in reinforced concrete (RC) frame structures. It considers the energy expended by the structure at each instant of lateral deformation to quantify damage in the structure through a simple damage index iE, which is the ratio of nonlinear energy expended at a deformation instant (on the pushover curve) to total nonlinear energy capacity of the structure. three definitions are considered to define damage index iE of the structure. these definitions are applied on pushover curves of two example 6 and 10 story RC bare frame buildings designed as per Indian seismic code. of the three definitions for the damage index iE, one with expended energy concept proved to be most appropriate, which reflects the true meaning of damage.
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    Mechanics-driven hand calculation approach for obtaining design P-M interaction curves of RC sections
    (01-09-2015)
    Majeed, Aysha Z.
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    A simple hand calculation based method is presented to develop axial flexure design P-M interaction curves of rectangular reinforced concrete sections. The proposed method uses basic principles of mechanics satisfying compatibility of strains, equilibrium of forces and constitutive relations of constituent materials. Simple step-wise calculation is enough to develop the interaction curve; it does not require any iterations. Accuracy of the method is demonstrated by comparing the results of two RC sections with the interaction curves of the sections obtained using SP:16. Step-wise calculations are presented of the two RC sections to illustrate the use of this method for generating design P-M interaction curves.
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    Seismic shear design of deep RC vertical members: A review of codal provisions
    (01-09-2010)
    Dasgupta, Kaustubh
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    The paper reviews seismic behaviour and performance of reinforced concrete (RC) deep vertical members, particularly bridge piers and structural walls. The provisions of the relevant Indian codes of practice, concerning shear strength and shear demand in these members, are reviewed in light of the provisions of international codes of practice. The deficiencies are identified in the seismic shear design philosophy, prescribed by Indian codes.
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    Seismic behaviour of RC moment resisting frame buildings designed and detailed as per first revision of IS 13920 draft provisions
    (01-04-2016)
    Sunitha, P.
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    Capacity design precludes brittle actions thereby maximising energy dissipation capacity of moment resisting frame buildings through flexural yielding in beams before possible yielding in columns during strong earthquake shaking. The flexural strength of columns is required to be more than that of beams framing into it. Seismic design codes stipulate guidelines for design and detailing of members to achieve desired ductile behaviour of buildings. This paper examines seismic behaviour of RC moment frame buildings in seismic Zone V and IV designed as per the column-to-beam strength ratio (CBSR) requirements of the draft IS 13920, and its adequacy along with the detailing requirements. The CBSR of 1.4 specified in the draft code is not sufficient for buildings in seismic Zone V.
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    When RC columns become RC structural walls
    (01-05-2011)
    Rohit, D. H.H.
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    Narahari, P.
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    Sharma, Rahul
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    Jaiswal, Arvind
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    IS 456:2000 and IS 13920:2002 distinguish columns from walls with both geometrical and empirical definitions that result in a sudden drop in the requirements of minimum longitudinal reinforcing steel at 0.4 cross-sectional aspect ratio or 2.5 length-to- width ratio. Designer wishing to offer economical designs would be tempted to use this ambiguity leading to unsafe designs. Therefore, to make structures safe and to check the lacunae in the codes, this paper argues in favour of having a gradual transition in the reinforcement requirement as the crosssectional aspect ratio changes from small to large. In light of international practice, the paper critically reviews IS codes' columns and walls reinforcement-detailing provisions and suggests possible improvements.
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    Superposition principle invalid in IS 13920 design of slender RC walls with boundary elements
    (01-03-2012)
    Rohit, D. H.H.
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    Narahari, P.
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    Jaiswal, Arvind Kumar
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    Current code IS 13920:2002 for ductile detailing of concrete structures assumes that moment capacity of a RC structural wall with boundary elements is the sum of moment capacity of the web portion of the wall and that due to the couple using axial capacity of the boundary elements and lever arm between them. This assumption leads to gross over-estimation of design moment capacity of the wall. In this paper, provisions are reviewed and improvements suggested eliminating this deficiency in the code provisions. A nonlinear method is suggested based on principles of mechanics for estimating the combined Pu-Mu strength envelope, considering the combined contribution of the web and boundary elements of the wall. Using this, a numerical study was performed of moment capacity of RC structural walls (both with and without boundary elements) to demonstrate that superposition principle is not acceptable in the design of RC structural walls with boundary elements.
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    Idealised bilinear moment-curvature curves of RC sections for pushover analysis of RC frame buildings
    (01-04-2016)
    Sunitha, P.
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    A simple approach is presented to derive limiting strain-based bilinear overstrength moment-curvature response curves of reinforced concrete sections. These curves are obtained by simple hand calculations proposed in the paper. Implications of use of these idealized curves are examined on estimating seismic behaviour of RC frame buildings by nonlinear static pushover analyses. The use of idealized moment-curvature curves and its properties, as proposed, offers a consistent and non- empirical approach compatible with actual section properties.
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    Seismic shear design of deep RC vertical members: Recommended provisions for Indian codes
    (01-09-2010)
    Dasgupta, Kaustubh
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    Based on the review of seismic shear design provisions of Indian codes for reinforced concrete (RC) deep vertical members (i.e., bridge piers and structural walls) in a companion paper, basic provisions are identified for shear resistance of RC sections. Draft provisions are presented for the consideration of the relevant Indian design code committees on bridge and building. The best seismic design practices seem to suggest that these provisions will be beneficial for the seismic performance of deep RC vertical members.
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    Expressions for moment of resistance of RC structural walls
    (01-10-2013)
    Rohit, D. H.H.
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    Jaiswal, Arvind Kumar
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    IS 456:2000 and IS 13920:2008 do not prohibit failure of RC structural walls by concrete in compression reaching the limiting strains. But, IS 13920:2008 (Annex A), which follows guidelines set by IS 456:2000, does not discuss the failure of RC walls under pure or almost pure compression of concrete in the P-M interaction curve. But, designers need the entire P-M diagram to be able to better understand the designs being proposed by them. In the determination of the ultimate moment of resistance (Ma), even when steel reaches the limiting strain first, secondary compression failure (εc=0.0035) is used as a basis (as has been customarily done in shallow RC beams and slabs) for arriving at the expressions for Mu. This is inadmissible in deep RC members, like structural walls. Tins paper presents expressions for Mu of RC walls, (1) based on basic principles of mechanics, namely equilibrium of the section, compatibility of strains and constitutive laws, (2) for all possible positions of neutral axis, and (3) without assuming secondary compression failure of RC members. Also, effect of concrete confinement by transverse reinforcement on P-M curve is presented; comparisons are presented of current method (unconfined) and proposed methods (unconfined and confined) of arriving at Mu and MΩ of RC structural walls.