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Research Interests

Research Highlights: The group focuses on developing new computational techniques in the areas of solid/fracture mechanics, finite element analysis, meshless methods, structural reliability, stochastic mechanics, structural dynamics, optimization etc. In addition, experimental studies on two-way hollow core reinforced concrete slabs is also undertaken.

A brief outline on the various research problems currently undertaken are provided below:

Fukushima 2011/Photo: AFP

Recent Publication

Shereena O.A., Nageswara Rao B. (2019) HDMR-Based Bayesian Structural System Identification. In: Rao A., Ramanjaneyulu K. (eds) Recent Advances in Structural Engineering, Volume 1, pp: 453-464, Lecture Notes in Civil Engineering, vol 11. Springer, Singapore
Shereena O. A., B. N. Rao: Dynamic System Identification using HDMR-Bayesian Technique. 2017 World Congress on Advances in Structural Engineering and Mechanics (ASEM17), Seoul,Korea · South Korea; 08/2017
Shereena O. A., B. N. Rao: HDMR Based Bayesian Structural System Identification. Tenth Structural Engineering Convention 2016 (SEC2016), CSIR-SERC Chennai, Chennai, India; 12/2016

Development of Robust Data Assimilation Techniques for Nonlinear Dynamical Systems

In the event of a nuclear accident, radioactive materials are released into the atmosphere causing radiological contamination of the environment and exposure to radiation which in turn poses potential danger to the public health and safety. In any radiological emergency system, the decision making team depends on the consequence assessment given by atmospheric dispersion models based Decision Support System, to choose on potentially effective countermeasures. However, model predictions rely on the availability of meteorological dispersion parameters and the source term emission data, both of which are difficult to be known accurately during a nuclear accident. The inherent uncertainties in these model parameters make it practically impossible to improve the model using traditional simulation methods. In recent years, data assimilation technique has been found to be very helpful for improving the model predictions. Using data assimilation technique, model predictions can be updated in real time by the measurement data, so they are more reliable and close to the real situation. However, when uncertainties in model parameters are the main source of prediction error, simultaneous estimation of model state and parameter is required. In recent years, various techniques, such as standard Kalman filter, and ensemble Kalman filter, have been applied to the state-parameter estimation problem. The main objective of the filtering problem is to estimate the current states of dynamical systems (lending themselves to representation by means of a state and observation/measurement equation) by using a set of observations available over time. In addition to radiological emergency system, many fields of scientific research, such as econometrics, geosciences, engineering, biogeochemical and hydrological modelling, the process of the systems by which the physical phenomena are represented is often hidden, and the available measurements about the process are restricted and contaminated by measurement errors. Although it is known that optimal solutions to the filtering problem can be obtained by calculating the probability density function conditioned on the available measurements , estimating the current states of highly nonlinear dynamical systems is quite complex and tedious in many cases because evaluating such distributions is practically impossible both analytically and numerically. Analytical solutions for nonlinear systems exist only for a small class of models, and numerical methods for linear systems with Gaussian error statistics often fail for the abruptly changing state estimation of systems exhibiting multi-normal states . Hence there is considerable interest in developing robust data assimilation techniques for nonlinear dynamical systems.

Layout of a typical precast prestressed concrete hollowcore slabs under fire conditions (Shakya et al.)

Structural behaviour of two-way prestressed hollow core slabs

A prestressed hollow core slab is also known as a voided slab or hollow core plank or simply typically used in the construction of floors in a multi-story building. Prestressed hollow core slab increases the efficiency of the structure. It is reinforced unlike conventional solid slab but prestressed at top and bottom. They are manufactured using high tensile strength prestressed strands or single wire which are embedded within the concrete slab. Prestressed hollow core slab has the advantage of a reduction in material and weight and savings in cost and construction time. Primary objective of the study is to evaluate the structural behavior of two-way prestressed hollow core slabs under shear and flexure.

Typical Vehicle-bridge interactive system

Recent Publication

Krishnanunni C. G., B. N. Rao, Decoupled technique for dynamic response of vehicle-pavement systems. Engineering Structures, Elsevier, DOI: 10.1016/j.engstruct.2019.04.042
G. Snehasagar., C.G. Krishnanunni., B. N. Rao, Dynamics of vehicle-pavement system based on a Viscoelastic Euler-Bernoulli beam model. International Journal of Pavement Engineering, Taylor and Francis Group of Journals, DOI: 10.1080/10298436.2018.1562189.

Dynamics of Vehicle-Structure Interactive Systems

The use of the vehicle-bridge interaction (VBI) data for structural health monitoring has received considerable interest in the last decade. A major advantage of these methods is that they use sensors mounted on the vehicle so that no sensors or data acquisition system needs to be installed on the bridge for health monitoring. The VBI based approach allows the target bridges to be monitored or assessed under operating conditions and hence the bridge need not be shut down for the process. Due to these reasons, the concept has the potential to be far more cost-effective than traditional structural health monitoring techniques. In addition to these, the separation of the content related to the bridge from content purely due to vehicle dynamics or road proﬁle can be troublesome. Due to these reasons, we focus on the development of a robust damage identiﬁcation algorithm for bridges by considering strategies to deal with the problems caused by road roughness, measurement noise and presence of other vehicles on the bridges. The procedure is based on the concept that a moving vehicle on the bridge can serve as both the exciter and receiver. For achieving these objectives, we focus on developing efficient numerical techniques for accurately modelling the vehicle-structure interaction dynamics. In the course of pursuing the above objectives, problems such as pavement roughness identification and vehicle parameter identification (inverse problems) are also undertaken. In short, we deal with numerical techniques to solve coupled partial differential equations of motion describing the vehicle-pavement or vehicle-bridge contact problems.

Parabolic trough collector installed at IIT Madras

Structural Analysis and Optimization of Solar Energy System

The renewable sources of energy are gaining importance in contemporary world due to plethora of problems arising from constant use of fossil fuels. Solar energy has emerged as its alternative to meet our energy requirements and parameters like cost and efficacy of devices should be considered and optimized to achieve the same. Over the past few years, the researchers have tried their best to make the most effective devices by investigating them from structural, thermal and optical outlook keeping in poise with the above constraints. One such device is parabolic trough, the basic building block of the solar collector system, which is low cost technology consisting of trough reflectors with a parabolic shape that concentrate the direct solar radiations onto an absorber tube located in the focal line of parabola. It is known that the power plant technologies using Parabolic Trough Collectors (PTCs) and high temperature receivers are one of the best options for concentrated solar power and process heat industry. Thus, predicting the optical performance of the trough is critical in the power plant design which is affected by structural deformation under the gravity and wind. The research work in this area includes the selection of suitable trough materials and the corresponding effect on the slope deviations, intercept factor, optical and thermal analysis of the parabolic trough collectors.

Simulated bistable shapes of thermally cured laminates

Recent Publication

Anilkumar P. M., A. Haldar, Eelco Jansen, B. N. Rao and R. Rolfes, Design Optimization of Multistable Variable-Stiffness Laminates, Mechanics of Advanced Materials and Structures, Taylor and Francis Group of Journals, DOI: https://doi.org/10.1080/15376494.2018.1512022
Anilkumar P. M., A. Haldar, E. L. Jansen, B. N. Rao and R. Rolfes, Effect of actuation procedure in MFC actuators for morphing of bistable laminates, 11th Structural Engineering Convention - SEC 2018, Jadavpur University, Kolkata, India; 12/2018.

Morphing Structures

Smart materials and structures are vastly becoming an integral part in engineering applications. Morphing multistable structures are treated as the computationally complex smart structures which can show reconfigurable stable shapes with respect to the changes in the surrounding loads. Growth of highly flexible, deployable structures demands the development of efficient techniques for analysis, design and control for morphing applications. Literature reviews shows that the extension on the use of smart morphing technology to large-scale deployable structures needs to fill up the gaps in smaller scale with the help of analytical, numerical models with experimental tools. The previous investigations available from literatures on morphing are focused on variation of the stiffness properties and the overall deformation between the states, with no concern for the intermediate stages during actuation. As the incorporation of dynamics characteristics of the structure is essential in the practical applications of morphing, further studies on the same would be of considerable interest and can be carried out. In practice, morphing structures need to be controlled in order to maintain or achieve a desired shape. To do so, an appropriate dynamic model has to be derived. During this process, structural characteristics should be investigated by considering the interaction between dynamic characteristics and the modes of actuation. In this work, the concept of static, smart and dynamic actuations will be exploited on both thermally and mechanically induced bistable laminates to further reduce the snap-through requirements.

Recent Publication

R. Suresh Kumar, B. N. Rao and K. Velusamy, “Bridging the Gap in Predicting the Crack Initiation of the Real Life Structures by Nuclear Class-1 Piping Design Philosophies and Full Scale Testing”, 14th International Conference on Fracture (ICF 14), June18-23, 2017, Rhodes, Greece.
R. Suresh Kumar, B. N. Rao, K. Velusamy, and Jalaldeen S, “Fatigue crack growth behavior of specimen level and component level geometries under cyclic bending", 02nd Second International Conference on Structural Integrity – ICONS2018, December 14-17, 2018, IITM, Chennai, India.

Development of the numerical prediction capability of the fatigue crack propagation behaviour of prototype sized pipe bend

Leak-Before-Break (LBB) demonstration is one of the most desirable safety features to be ensured for meeting the structural integrity of the Sodium-cooled Fast Reactor (SFR). SFR piping system subjected to many cyclic loading conditions due to the various stages of its operation. It leads to nucleation of microscopic crack at the area of the highly stressed portion and its growth leads to the leakage of the pressure boundary. In the case of Indian SFR system, LBB demonstration is ensured as per the guidelines of RCC MRx A16 or by experimental methods. RCC MRx A16 guidelines are conservative in nature and conducting experiments on full-scale components has always been economically expensive. Experimentally validated numerical tool can perform a fast, economic and reliable information which are required for demonstrating the structural integrity of the SFR piping systems from the LBB point of view. In this research, it is planned to develop a numerical method, which can predict the crack propagation behaviour of the component type of geometries within engineering accuracy. Validation is planned with the available literature data as well as full-scale experimental results. The essential full-scale experiment on a pipe bend under cyclic bending and the numerical simulation are under progress.

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