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Free vibration behaviour of thin-walled concrete box-girder bridge using Perspex sheet experimental model

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Verma V. , Nallasivam K.

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tom Vol. 106, nr 2

56--76

EN

Purpose: Curved box-girder bridges offers an excellent solution to the problems associated with traffic congestion. However, owing to their complex geometry, they are subjected to shear lag, torsional warping and cross-sectional distortion, which must be assessed in their study and design. Furthermore, the dynamic behaviour of curved bridges adds to the complexity of the issue, emphasizing the importance of studying free vibration. The purpose of this study is to numerically model the concrete curved box-girder bridge considering torsional warping, distortion and distortional warping effects and to identify key parameters that influence the free vibration response of the box-girder bridge by validating it with experimental and analytical studies. Design/methodology/approach: The concrete bridge is numerically modelled by means of computationally effective thin-walled box-beam finite elements that consider torsional warping, distortion and distortional warping, which are prominent features of thinwalled box-girders. The free vibration analysis of the concrete curved box-girder bridge is performed by developing a finite element based MATLAB program. Findings: The identification of critical parameters that influence the free vibration behaviour of curved thin-walled concrete box-girder bridges is one of the main findings of the study. Each parameter and its effect has been extensively discussed. Research limitations/implications: The study limits for the preliminary design phase of thin-walled box-girder bridge decks, where a complete three-dimensional finite element analysis is unnecessary. The current approach can be extended to future research using a different method, such as finite element grilling technique on multi-span curved bridges having unequal span. Originality/value: The current research implements a finite element formulation in combination with thin-walled beam theory, where an extensive parametric study is conducted on the free vibration behaviour of a concrete thin-walled box-girder bridge, while also accounting for their complex structural actions. The validity of the given numerical formulation is demonstrated by a comparison of the natural frequencies found experimentally. The study carried out will be of great importance for engineers to help them anticipate the modal characteristics of a curved concrete thin-walled girder bridge, which will further be useful for evaluating their dynamic response analysis.

2

Magnetic navigation and tracking of multiple ferromagnetic microrobots inside an arterial phantom setup for MRI guided drug therapy

80%

Kumar N. , Verma V. , Behera L.

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2017

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tom Vol. 37, no. 3

347--356

EN

Magnetic steering of ferromagnetic microrobots facilitates active drug targeting and minimally invasive treatment of deep seated tumour cells. Several techniques for magnetic steering of nanostructured single microrobot in human vasculature exist but literatures on multirobot navigation are scarce. In the current work, preliminary experimental validation of a novel magnetic navigation model for multiple ferromagnetic microrobots is performed inside a bifurcated arterial phantom apparatus. The proposed model includes the formation of a single linear assembly of ferromagnetic microrobots inside the arterial setup placed under a magnetic field. This field is intended to mimic the magnetic field generated by a Magnetic Resonance Imaging (MRI) device which finds application in targeted drug therapy. The linear assembly process was studied with the help of Newtonian dynamics simulation including dipole–dipole and near field forces. As, the assembly was found to be structurally intact in a pulsatile flow, its simulated trajectory was controlled by manipulating a single microrobot present in the middle of the assembly. The trajectory convergence algorithm used for this purpose includes a fuzzy logic based nonlinear ‘‘Proportional-Integral-Derivative’’ (PID) control scheme with magnetic field gradient as its control input. Since most of the modern MRI devices are based on PID controller for manipulation of magnetic gradients, the proposed fuzzy PID based control scheme can easily be interfaced with these devices for the intended application.

3

Architecture-based Optimal Software Reliability Allocation under uncertain preferences

80%

Aggarwa A. G. , Verma V. , Anand S.

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2018

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tom Vol. 14

3--12

EN

Reliability Allocation in an essential task of the software development process. Increasing complexities in software structure and demand for bug free software has made Reliability Allocation a mandatory task during design and planning phase. So far in the literature several methods and models have been discussed for achieving the reliability target based on user's and developer's point of view. The crucial question that arises is ‘How to allocate reliability for a Software system in an uncertain atmosphere where developer's preferences are subjective in nature?''. In this paper, we have proposed the software reliability allocation problem incorporating the decision maker's subjective uncertain preferences using Ordered Weighted Averaging (OWA) approach based on Fuzzy Analytical Hierarchical Process (FAHP).Parameter determination using FAHP through architectural hierarchy of the software system helps in interaction of user's assessment with the software engineers and programmers outlook. The OWA technique ensures complete use of available information and also avoids any kind of biasedness in reliability allocation due to overestimation of developer's inclinations. The proposed MEMV-OWA (Maximum Entropy Minimum Variance) operator is a bi-objective mathematical programing problem that maximizes entropy (deployment of information) along with minimization of the variance in weighting vector in an uncertain environment. Reliability allocation procedure for software system using the anticipated process has been discussed in detail. Also precise demonstration of the procedure has been done with an application example.