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1

Effect of seepage on change in stress distribution scenario in static and seismic behaviour of earthen dams

Nandi N., Roychowdhury A., Dutta S. C.

International Journal of Applied Mechanics and Engineering

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2018

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Vol. 23, no. 1

121--136

EN

The present study makes an effort to understand the damage of earthen dams under static and seismic loading condition. To make the investigation more realistic, behaviour of earthen dams considering the occurrence of a phreatic line indicating the submerged zone due to seepage within the dam body is considered. In case of earthen dams, homogeneous or nonhomogeneous, the consideration of the occurrence of a phreatic line or seepage line through the dam body is an important part of the earthen dam design methodology. The impervious material properties in the submerged zone below the phreatic line due to seepage may differ a lot in magnitudes as compared to the value of the same materials lying above this line. Hence, to have the exact stress distribution scenarios within the earthen dam, the different material properties above and below the phreatic line are considered in this present study. The study is first carried out by two-dimensional as well as three-dimensional finite element analysis under static loading condition. The work is further extended to observe the effect of seepage due to the consideration of the phreatic line on dynamic characteristics of earthen dams. Free vibration analysis and seismic analysis based on the Complete Quadratic Combination (CQC) method by considering twodimensional and three-dimensional modeling are carried out to present the frequencies, mode shapes and the stress distribution pattern of the earthen dam.

2

Applicability of a few analytical formulations for dynamic characteristics of elevated tanks with battered stagings

Dutta S. C., Roy R., Dutta S.

International Journal of Applied Mechanics and Engineering

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2004

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Vol. 9, no 4

803-819

EN

The applicability of available analytical formulations for elevated tanks with vertical stagings is shown to the similar tanks with battered stagings. The formulation includes the dynamic characteristics like lateral and torsional stiffness and natural periods. Both frame and shaft supported stagings for elevated tanks are considered with and without accounting for the effect of soil-structure interaction. The values obtained through analytical formulation are compared to the results of finite element analysis and found to have reasonable performance. Thus the study yields handy formulations to be used for seismic design of elevated tanks with battered stagings.

3

Effect of strength and stiffness deterioration on seismic behaviour of R/C asymmetric buildings

Das P. K., Dutta S.C.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, no 2

527-564

EN

Past earthquakes (e.g., 1985 Mexico earthquake) have demonstrated the severe seismic vulnerability of asymmetric buildings due to coupled lateral-torsional vibration in elastic as well as in inelastic range, even under a purely translational ground shaking. Extensive research effort on inelastic behaviour of asymmetric buildings has generally used an elasto-plastic or bilinear hysteresis behaviour for the structural load-resisting elements, ignoring the strength and stiffness deteriorating characteristics of RC structural elements under cyclic loading. Hence, these studies could not recognize the possibility of progressively increasing torsional damage of load resisting elements near one edge, due to continuous shifting of centre of resistance caused by such degradations during inelastic excursions. The present study on asymmetric one storey building systems aims to assess these possible detrimental effects. The system responses are studied using a) elasto-plastic, b) stiffness degrading, c) strength deteriorating, and d) stiffness degrading as well as strength deteriorating hysteresis models for the load-resisting elements. These responses are expressed in terms of the maximum displacement demand and hysteretic energy demand in load-resisting elements. Variations of these two response quantities are studied for feasible ranges of influencing parameters due to each of the four hysteresis behaviours. The results are compared to understand the effects of stiffness degradation and strength deterioration. The remedial measures are also outlined to control the excessive response found to be generated due to such degradation effects. The study may prove useful to arrive at more justified torsional code provisions.

4

Differential settlement among isolated footings of building frames: the problem, its estimation and possible measures

Roy R., Dutta S. C.

International Journal of Applied Mechanics and Engineering

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2001

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Vol. 6, no 1

165-186

EN

The conventional design of building frames is based on the assumption that the settlement of footings has no effect on the load of the corresponding columns. In reality, the differential settlements among various footings result in a redistribution of the column loads, the amount of which depends on the rigidity of the structure and the load-settlement characteristics of the soil. The present paper attempts to study the effect of the same on design force quantities for frame members of building frames with isolated footings. The nonlinear settlement versus stress relationship arising in case of building frames with isolated footings on clayey soils is attempted to be dealt with two alternative iterative approaches. Results of a few simple three-dimensional frames obtained by the simpler approach are compared with the results of the more rigorous approach and found to be satisfactory. Frames resting on sandy soil are also studied by idealising the soil medium below the footing as linear elastic springs. Various representative case studies are presented for frames resting on sandy and clayey soil. These case studies may help in arriving at design provisions to account for such effects. The simpler iterative approach may be exercised with the help of available commercial frame analysis software and may prove useful in improved design of buildings accounting for the effect of soil-structure interaction. Adequacy of providing tie beams, continuous lintels, and diagonal braces in minimising the redistribution of force quantities are also studied and presented in the paper in limited form. The addition of diagonal braces are found to be effective in substantially minimising the change in force quantities due to the soil-structure interaction.