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RISS 인기검색어
- 검색키워드
- 저자 : Rajib Saha (검색결과 4 건)
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Effect of raft and pile stiffness on seismic response of soil-piled raft-structure system
Rajib Saha,Sekhar C. Dutta,Sumanta Haldar 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.1
Soil-pile raft-structure interaction is recognized as a significant phenomenon which influences the seismic behaviour of structures. Soil structure interaction (SSI) has been extensively used to analyze the response of superstructure and piled raft through various modelling and analysis techniques. Major drawback of previous study is that overall interaction among entire soil-pile raft-superstructure system considering highlighting the change in design forces of various components in structure has not been explicitly addressed. A recent study addressed this issue in a broad sense, exhibiting the possibility of increase in pile shear due to SSI. However, in this context, relative stiffness of raft and that of pile with respect to soil and length of pile plays an important role in regulating this effect. In this paper, effect of relative stiffness of piled raft and soil along with other parameters is studied using a simplified model incorporating pile-soil raft and superstructure interaction in very soft, soft and moderately stiff soil. It is observed that pile head shear may significantly increase if the relative stiffness of raft and pile increases and furthermore stiffer pile group has a stronger effect. Outcome of this study may provide insight towards the rational seismic design of piles.
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Indrajit Dey,Rajib Saha,Swarup Kumar Ghosh 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7
The influence of isothermal holding (IH) near the pearlite start temperature (Ps≈610 °C) and above the martensite starttemperature (Ms≈245 °C) were studied in two hot-rolled (FRT≈1000 °C) high carbon steels, without (HC0) and with Nbmicroalloying (HC1). Optical microscopy (OM), field emission scanning electron microscopy (FESEM) and high-resolutiontransmission electron microscopy (HRTEM) were utilised for observing the microstructural constituents whereas, nanoindentationand microindentation were performed to estimate the average hardness and elastic modulus values of various phaseconstituents. It has been observed that hot deformation in the austenite region results in the formation of a dual phase-typemicrostructure consisting of fine pearlite lamella and ferrite grains with some amount of degenerated pearlite. IH at 570 °Cleads to a higher volume percentage of ferrite and coarsening of pearlite whereas, IH at 300 °C results in mixed phases comprisingbainite, a very low amount of martensite/retained austenite (M/RA), pearlite and some amount of ferrite. Hot rolledmicroalloyed steel when isothermally held near the Psresults in a significant enhancement of ductility than hot rolled andair-cooled condition while sacrificing tensile strength marginally, which may be attributed to a higher percentage of ferriteand refinement of pearlite due to Nb addition. The estimated yield strength values correlate well with those experimentalyield strength values, but a little discrepancy has been noticed for the ultimate tensile strength values. Possible interpretationsare suggested in this paper.
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Low Cycle Fatigue Performance and Failure Analysis of Reinforcing Bar
Md Abu Bakkar,Rajib Saha,Debdulal Das 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12
Low cycle fatigue (LCF) behaviour and associated failure mechanisms of a thermo-mechanically treated Fe 500D steel rebarhave been experimentally evaluated with a view to assess its performance under seismic condition. The total axial straincontrolledLCF tests have been performed at five different strain amplitudes (± 0.30 to ± 1.00%) at ambient temperature untilfailure maintaining a constant true strain rate of 1 × 10− 3 s− 1 and a fixed strain ratio of − 1. Fatigue data have been analysedfollowing both strain–life and plastic strain energy–life relationships; while, macro as well as micro features of the failedspecimens, have been critically examined. These are supplemented by microstructural characterizations in addition to tensileand hardness measurements. Significant reduction of yield strength is recorded under dynamic loading which is responsiblefor considerable cyclic softening of rebar till failure in all strain amplitudes indicating the deterioration of seismic resistanceproperty. Both strain–life and plastic strain energy–life relationships are found to accurately predict the cyclic plasticbehaviour of the selected rebar. A near Masing behaviour is established by three different analytical approaches. The fatiguecrack is always found to initiate at the transverse rib root and primarily propagates alongside the rim region.
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