Conference Papers
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Item Modeling and experimental studies on the dynamics of bolted joint structure: Comparison of three vibration-based techniques for structural health monitoring(Springer Science and Business Media Deutschland GmbH info@springer-sbm.com, 2020) Deka, A.; Rao, A.; Kamath, S.; Gaurav, A.; Gangadharan, K.V.Detection of inadequate tightening in bolted joints is quintessential to ensure structural rigidity and to prevent catastrophic failure. Studies show that 30% of assembly failures occur due to inadequate tightening. In the present study, three vibration-based techniques are presented and compared to detect inadequate tightening of bolted joints. Variation in the damped natural frequency, variation in the damping ratio, and variation in the dynamic joint stiffness are studied with varying tightening torques in the bolted joint. The results show that all the three dynamic parameters vary with the tightness of the bolted joint. Dynamic joint stiffness varies significantly as opposed to the damping ratio and damped natural frequency as tightening torque reduces. In order to verify the results of dynamic stiffness method, ANSYS is used to model and analyze the joint. The experimental setup used to calculate the parameters consists of two Euler–Bernoulli beams connected with single lap bolted joint. © Springer Nature Singapore Pte Ltd 2020.Item Effects of High Cyclic Strains on Dynamic Properties of Cohesionless Soils(Springer Science and Business Media Deutschland GmbH, 2025) Akarsh, P.K.; Chaudhary, B.; Sajan, M.K.; Chikkanna, T.; Talkad, P.Soils can experience large cyclic shear strains (>1%) under dynamic loading circumstances such as earthquakes. Determining dynamic properties such as damping ratios and shear modulus is crucial in the design of earthquake-resistant structures. From past studies, it was understood that the dynamic behaviour of soils at higher strains (>0.01%) is different from soils subjected to lower strains (<0.001%) because of nonlinear stress–strain behaviour and damping characteristics at higher strains. Furthermore, it was evident that the majority of tests were carried out on lower strains and only few numbers of studies were reported on tests for higher strains. Hence in this study, the dynamic properties for locally available cohesionless soils tested under high cyclic strains are presented. Generally, the dynamic properties were determined up to strain levels <1% considering a symmetrical hysteresis loop. But the loop becomes asymmetric as the strain level increases and due to which, dynamic properties are over-estimated. So, in this study, the dynamic properties of saturated sand were determined by an actual asymmetric hysteresis loop. Strain-controlled cyclic triaxial tests were conducted on reconstituted soil specimens at a low frequency (0.25 Hz) for variable peak strain levels (0.15–1.5%). The specimens were prepared at different relative densities (30–90%) and consolidated at an effective confining pressure of 100 kPa. The findings of the study revealed that the soil’s shear modulus would degrade more quickly or that the modulus reduction ratio would reduce at higher strain levels (γ ≥ 1%) due to an increase in pore water pressure during undrained cyclic loading. It also turns out that at higher strain values (>1%), the damping ratio significantly decreased. Hence, it is not obvious to extrapolate the trend seen for γ < 1% to get the results for γ > 1%. This work would be helpful for geotechnical practicians and researchers to have insights into the existing methodology for finding the dynamic properties of cohesionless soils at higher cyclic strains. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.