Conference Papers

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    Implementation of Acoustic Emission Testing to Study the Type of Cracking in Reinforced Concrete Beams
    (Springer Science and Business Media Deutschland GmbH, 2021) Ghosh, S.; Agrawal, R.; Vidya Sagar, R.
    In this experimental study, crack classification in reinforced concrete (RC) beams was carried out using acoustic emission (AE) testing. Two types of under reinforced RC beams were tested in laboratory subjected to four-point bending, and monotonically increased load was applied. The first type of RC beam had shear reinforcement (steel stirrups), and the second type of RC beam had no shear reinforcement. The generated AE during the fracture process in the tested RC beams were used for the crack classification analysis. Gaussian mixture modeling (GMM) of acoustic emission signals was performed. It was observed that the RC beam without shear reinforcement failed suddenly (brittle nature). However, the RC beam with shear reinforcement failed gradually thereby exhibiting ductile nature. In both the RC beams, considerable AE related to shear cracking appeared at a 20–30% peak load. In the case of the RC beam with shear reinforcement, initially, tensile cracks were developed at the bottom of the beam and slowly started widening upward. Diagonal shear cracks started forming near to the supports when the test specimen reaching to collapse. In the case of the RC beam with no shear stirrups, tensile cracks originated at the bottom of the beam. But in this case, the influence of shear cracks developed near to the supports was more pronounced as it propagated rapidly. By comparing the different AE parameters, a steady increase in the number of hits till failure was observed in the case of the RC beam with shear reinforcement. But on the other hand, an abrupt increase in the number of hits was observed after 50% of peak load in the case of the RC beam with no shear reinforcement. The results are useful to study the sensitivity of AE to the shear reinforcement present in the RC beams. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Numerical study on fracture behavior of alkali activated concrete mixes for different beam sizes
    (Elsevier Ltd, 2023) Annappaswamy, G.M.; Channappa, T.M.; Prashanth, M.H.
    The present study considers the use of AAC mixes, since the raw materials that are being used to produce concrete are non-renewable natural resources, particularly Ordinary Portland Cement (OPC). Also, production of OPC contributes a greater amount of CO2 to the environment. Hence, an attempt has been made to study alternative construction materials keeping in mind sustainable development. The present numerical study compares the fracture behaviour and size effect of Alkali Activated Concrete (AAC) mixes with Ordinary Portland Cement Concrete (OPCC) mixes by numerically modelling the beams of AAC and OPCC using FEA software ABAQUS. Three different mixes of AAC, characterized by the variation of percentage volume of water-quenched slag (WQS) as a substitute for Natural sand (RS) and one OPCC mix, were studied. A three-point bending test was performed in ABAQUS for the beams of three different sizes, which are geometrically similar with constant thickness. Numerical simulation is performed under displacement control. Load versus CMOD graphs are plotted from the output data obtained from the numerical modelling. Fracture parameters such as Fracture energy (GF), Brittleness number (B), Characteristic length (lch), and Stress intensity factor (KIC) are then calculated from the obtained data and compared to understand the influence of fracture properties and size effect on the behaviour of structural elements since limited research works are available from the literature. From the results, it is observed that OPCC mixes show superior strength, high resistance to crack propagation, more toughness, and high fracture energy when compared to AAC mixes. AAC-50 concrete mix has shown better performance compared to the other two AAC mixes, i.e., AAC-0 and AAC-100. The results of this work can certainly be used to predict the non-linear behaviour of concrete and can be adopted in the design of structural elements. © 2023 Elsevier Ltd. All rights reserved.