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Devdas Menon

Other affiliations: Indian Institutes of Technology
Bio: Devdas Menon is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topic(s): Deflection (engineering) & Beam (structure). The author has an hindex of 10, co-authored 50 publication(s) receiving 388 citation(s). Previous affiliations of Devdas Menon include Indian Institutes of Technology.
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Journal ArticleDOI
Abstract: This paper discusses the dynamic response of a typical prestressed concrete railtrack sleeper due to wheel–track interaction dynamics, involving wheel and rail imperfections, under various parametric conditions. The interaction dynamics of the vehicle and track is first carried out in the time domain using MSC/NASTRAN. Using the resulting load time histories on an isolated sleeper, a detailed finite element model of the sleeper is used to analyze its dynamic behaviour. The dynamic amplification factors for deflection, ballast pressure and bending moments have been evaluated at the critical section (rail-seat and centre) for various exciting frequencies under different vehicle–track parametric conditions. The results provide a basis for improved and rational design of the sleeper.

81 citations


Journal ArticleDOI
Abstract: ‘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.

71 citations


Journal ArticleDOI
TL;DR: A transformation invariant approach using copula functions is proposed for the multivariate simulation of dependent axle weights of different vehicle classes and is found to be in very good agreement with the observed data.
Abstract: Safety assessment and rational design of bridge structures requires the uncertainty associated with vehicle loads to be modeled as accurately as possible. This modeling is rendered difficult by the presence of vehicle axle weights that involve different combinations of unimodal and multimodal probability distributions with different dependence structures. In this paper, a transformation invariant approach using copula functions is proposed for the multivariate simulation of dependent axle weights of different vehicle classes. Copula based dependence modeling, which is widely used in the financial risk analysis, is applied to model and simulate three different vehicle cases with different combinations of marginal probability distributions for axle weights. The database of observed vehicle weights is based on the data collected at five locations on national highways in India. The dependence between multimodal distributions of axle weights is accurately considered and simulations are carried out. The simulated axle weights are found to be in very good agreement with the observed data. This type of simulation is useful in carrying out simulation-based reliability analysis of bridges and pavements.

28 citations


Journal ArticleDOI
Abstract: This paper reviews the prevailing international codal recommendations to determine the design along-wind moments in reinforced concrete (RC) chimneys and towers. A comparative study reveals significant disparities among the various codal estimates of the design moments, given the same basic wind speed and terrain condition. These disparities are a matter of concern to practising chimney designers and approving authorities in many countries. The relative accuracy of these differing estimates, which are based on different gust factor methods, have been quantitatively assessed with reference to rigorous stochastic dynamic analyses. This study covers a number of linearly tapered RC chimneys with heights in the range 100–400 m, located in different terrain conditions and subject to the range of wind speeds encountered in practice. It is observed that the estimates of the design moments are generally conservative in varying degrees, and are unconservative only in some cases. In very rough terrains, the lack of appropriate design provisions results in extremely conservative designs. With a view to improving the accuracy in the predictions, modifications to the gust factor method have been proposed in this paper.

21 citations


Journal ArticleDOI
Abstract: The present study reports the results of a rigorous dynamic interaction analysis that accounts for the vehicle-track characteristics and rail imperfections. In order to perform a rigorous dynamic analysis, a model involving all components of the track structure and vehicle parameters are required. A vehicle model (conforming to Indian Railways) with 17 degrees of freedom has been considered. The track model consists of rail, rail-pad, sleeper, ballast, sub-ballast, subsoil and a track length encompassing 12 prestressed concrete sleepers. The dynamic interactive analysis is carried out between the vehicle and track in the time domain using a finite element software. The results of the interactive analysis give responses in the form of reaction time histories at the rail-seat locations during the passage of vehicle. A parametric study is carried out to assess the influence of different track parameters on the dynamic load on the railtrack sleepers. Based on this study, suitable load amplification factors are arrived at to facilitate an improved design basis for an equivalent static analysis in practical designs of sleepers.

17 citations


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Journal ArticleDOI
Abstract: Train and track interactions during services normally generate substantial forces on railway tracks. Such forces are transient by nature and of relatively large magnitude and are referred to as impact loading. There has been no comprehensive review of the typical characteristics of the loading conditions for railway track structures, in particular, impact loads due to the wheel/rail interaction, published in the literature. This paper presents a review of basic design concepts for railway tracks, abnormalities on tracks, and a variety of typical dynamic impact loadings imparted by wheel/rail interaction and irregularities. The characteristics of typical impact loads due to wheel and rail irregularities, e.g. rail corrugation, wheel flats and shells, worn wheel and rail profiles, bad welds or joints, and track imperfections, are presented with particular emphasis on the typical shapes of the impact load waveforms generally found on railway tracks. Copyright © 2007 John Wiley & Sons, Ltd.

256 citations



01 Jan 1998-
TL;DR: The static and dynamic approaches to the determination of design wind loads have been summarised along with the various assumptions, approximations and limitations involved.
Abstract: The static and dynamic approaches to the determination of design wind loads have been summarised along with the various assumptions, approximations and limitations involved. The application of these two approaches using the Australian Standard AS1170.2 is discussed along with comparisons from wind tunnel measurements.

147 citations


Journal ArticleDOI
Abstract: The vibration of in situ concrete sleepers in a railway track structure is a major factor causing cracking of prestressed concrete sleepers and excessive railway track maintenance cost. Not only does the ballast interact with the sleepers, but the rail pads also take part in affecting their free vibration characteristics. This paper presents a sensitivity analysis of free vibration behaviors of an in situ railway concrete sleeper (standard gauge sleeper), incorporating sleeper/ballast interaction, subjected to the variations of rail pad properties. Through finite element analysis, Timoshenko-beam and spring elements were used in the in situ railway concrete sleeper modeling. This model highlights the influence of rail pad parameters on the free vibration characteristics of in situ sleepers. In addition, information on the first five flexural vibration modes indicates the dynamic performance of railway track when using different types of rail pads, as it plays a vital role in the cracking deterioration of concrete sleepers.

144 citations


Journal ArticleDOI
01 Mar 2005-
Abstract: Ballasted railway tracks will settle as a result of permanent deformations in the ballast and in the underlying material layers. The settlement is caused by the repeated traffic loading and the sev ...

114 citations


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Performance
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Author's H-index: 10

No. of papers from the Author in previous years
YearPapers
20211
20206
20196
20184
20171
20162

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Author's top 5 most impactful journals

Aci Structural Journal

7 papers, 35 citations

The Indian Concrete Journal

5 papers, 12 citations

Engineering Structures

4 papers, 104 citations

Structural Engineering and Mechanics

3 papers, 10 citations