Amar Prakash

Fuzzy Similarity Approach for Ranking and Health Assessment of Towers Based on Visual Inspection

The most common way for the health assessment of existing telecommunication towers is through visual inspection. However, the results of the visual inspection are highly subjective and are merely based on perception which may differ grossly from one expert to another. One of the best ways to normalize human perception and reasoning in decision making is through fuzzy logic. This paper presents a fuzzy approach towards health assessment and ranking of telecommunication towers based on visual inspection. The health assessment of tower is treated as a group multicriteria decision making (MCDM) problem in which the towers are rated by expert group based on different criteria. The model used in the paper is a modified version of fuzzy technique for order preference by similarity to ideal solution (TOPSIS). The modified version rank the towers based on similarity with fuzzy positive ideal solution (FPIS) rather than the distance from fuzzy positive and negative ideal solutions. The model also provides critical information about the issues which need to be addressed to maintain the health of the towers and thereby enables efficient management and allocation of the limited resources. An illustrative example is included to clearly describe the steps involved in the process. Finally, sensitivity analysis for the model is carried out. The results of the sensitivity analysis demonstrate the tolerance of the model for slight variation in the input parameters, which typically reflect the doubt or confusion in the mind of expert while rating. The method is also compared with the closeness coefficient method and is found to be more appropriate for the ranking of towers. The model attempts to bring some rationality to the vagueness involved in visual inspection. The model is an effective tool for health assessment and ranking of towers based on visual inspection.

Dynamic Subsidence Characteristics in Jharia Coalfield, India

Surface ground movements are usually described by a number of characteristic indices such as vertical displacement, horizontal strain and slope, which are an inevitable consequence of underground mining. Every point at the surface over a panel is subjected to strain and slope during mining and its investigation is essential to assess the safety of surface structures. Therefore, the behaviour of dynamic active and residual subsidence was studied for a few panels of Jharia coalfield. The subsidence and slope were linearly related to time. Compressive and tensile strains showed typical fluctuating characteristic behaviour. The rate of mining being a key and controlling parameter for rate of subsidence their inter-relationship was developed, which showed a rational trend. Compressive and tensile strains and slope showed poor correlation with rate of face advance.

Multivariate statistical approach for assessment of subsidence in Jharia coalfields, India

Indian coalfields, one of the major coal producers, are facing serious problem of subsidence now-a-days. This paper attempts to investigate various factors and their influence on magnitude and extent of subsidence. The study was conducted in the Jharia coalfields, India where extraction of thick seams at shallow depths has damaged the ground surface in the form of subsidence. For precise pre-estimation of subsidence, it is therefore necessary to know the contribution of each factor to the occurrence of subsidence. In order to achieve the objectives of this study, several multivariate statistical techniques such as factor analysis (FA), principal component analysis (PCA) and cluster analysis (CA) have been used. Two factors were extracted using FA. Factor 1 and factor 2 account for 42.327% and 24.661% of the variability respectively. Factor 1 represents “natural factor” whereas factor 2 represents “subsidence coefficient”. Spatial variations in regarding susceptibility to the subsidence were determined from hierarchical CA using the linkage distance. Further, the findings of this study would be helpful for prediction of magnitude of subsidence empirically.

Prediction of Behavior of Ceramic/Metal Composite Panels Under Two Consecutive Ballistic Impacts

This article presents a numerical investigation to predict the behavior of ceramic (Al2O3 99.5)/metal (Al5083 H116) composite panels under two consecutive high-velocity impacts of 7.62 mm sharp-nosed small projectiles. A numerical model is developed using the advanced nonlinear software AUTODYN. The aim of the study is to predict the impact behavior of ceramic/metal composite panels. The study mainly focuses on the effect of arrangement of front ceramic tiles having collinear and non-collinear joints on the impact damage pattern. The novelty of the study presented in this article is the prediction of high-velocity-impact response under two consecutive and closely spaced hits on composite panels carried out in a more realistic manner. Numerical responses, such as depth of penetration, and deformation in back plate and crack patterns, are found to match well with the experimental results. It is believed that the outcome of this study is helpful in the design of a ceramic tile joint arrangement to minimize damage in the target panel.

A safe depillaring design for shallow depth of cover with influence of surface ground movements: a study in Jharia Coalfield

Extraction of coal from a shallow depth of cover especially under multi-seam mining condition requires intensive precautions in respect to safe working and impact on surface structures. A detailed geotechnical investigation is imperative for the design of a suitable support system during depillaring operation. A study has been exercised in Maheshpur colliery of Jharia Coalfield to assess the stability between the parting of VIIIA and VIIIB seams through numerical modeling. The support systems have been framed for split galleries, slices, and goaf edges with the help of well-established Central Mining Research Institute-Indian School of Mines rock mass rating (CMRI-ISM RMR) and NGI-Q system. A suitable method of depillaring has been designed keeping in view the safety of surface structures in respect to subsidence.

The assessment of high velocity multi-impact damage in steel fiber reinforced cementitious composite panels

This paper presents a high velocity impact damage assessment of 100 mm thick steel fiber reinforced cementitious composite (SFRCC) panels of size 300 mm × 300 mm. The panels are tested using in-service munitions in field firing range under high velocity impacts of 5.56 mm and 7.62 mm calibre projectiles. Three consecutive normal impacts are made on each of the SFRCC panel within the damage zone of previous hits. The details of impact tests, procedure adopted for multi-impact damage assessment are described in the paper. Measurements are taken for depth of penetration, location of cracks, and crater sizes under first hit, as well as after consecutive hits. In order to quantify the damage in SFRCC panels under multiple impacts, both non-destructive testing (NDT) and destructive methods are adopted. For quantitative assessment of the internal overlapping damage zones, NDT using ultrasonic pulse velocity (UPV) measurement on a square grid spacing of 20 mm is carried out. Internal overlapping of damage zones due to multi-impacts on SFRCC panels are identified in non-destructive manner. To verify the effectiveness of the NDT method in multi-impact damage assessment, few SFRCC panels are dissected, using concrete cutting machine. Numerical simulation is also carried out to predict damaged area in the panels under multi-impacts. The damage contours obtained from numerical simulations are found to match with the damage zones detected using NDT method.