Nonlinear seismic behaviour of steel planar moment-resisting frames

The nonlinear response of steel planar moment-resisting frames during strong earthquakes poses a strong need for accurately modelling inelastic behaviour and large displacements. This thesis attempts to provide realistic and efficient analytical tools to aid this study. Two large -displacement small-strain beam-column models are employed to include material and geometric nonlinearities. The first model assumes lumped plasticity, and discretises an element into segments. Axial force-Bending Moment strength interaction and flexural bowing are considered. Ten characteristic segment states are identified. An efficient numerical scheme is suggested to solve the nonlinear governing equations. This model only approximately represents the strength and stiffness of beam-columns. A comprehensive finite element beam-column model is developed to more accurately model the strength and stiffness. A beam-column is discretised into segments, and further, each segment into one-dimensional fibres. A uniaxial cyclic constitutive law valid under arbitrary transient loading is proposed for structural steel. This physically motivated law incorporates the initial yield plateau, and provides explicit expressions for stress in terms of strain throughout the hysteretic path. This law is used to control the hysteretic loading of fibres. A simple semi-empirical model is employed to analytically describe the highly nonlinear hysteretic behaviour of flexible joint panel zones in steel planar frames. Some modelling assumptions that may be made in frame analyses are evaluated. Numerical study of a building frame with flexible joints indicates that its collapse is sensitive to the joint panel zone design in addition to the ground motion

A Solution to the Inverse Problem in Ocean Acoustics

The methodology and software developed to reconstruct a vertical sound speed profile as a part of studies on the marine acoustic modelling, using the ray path lengths and the travel time perturbations in tomographic layers are outlined. For a stratified ocean, considering the range independent nature of the medium, geophysical inverse techniques are employed to reconstruct the sound speed profile. The reconstructed profile for a six layer ocean, with five energetic modes, is in good agreement with that of the assumed profile thereby indicating the usefulness of the model. The effect of noise caused by the excursions of the source and receiver moorings; When expressed in terms of travel-time differences, results in the sound speed changes up to 0.1 percent

Chemical composition and size distribution of atmospheric aerosols over the Deccan Plateau, India.

Measurements on atmospheric total aerosol were made at Poona during the summer and winter seasons of 1978–79. An Andersen particle sampler Model 20–810, Mark II (Andersen 2000 Inc. U.S.A.) which samples atmospheric particles with diameters ranging between 0.4 and 10.0 μm was used for the measurement. The mass distribution of the total aerosol, and separately for the chloride, sodium, ammonium, sulphate and nitrate components were obtained. The mass distribution of the aerosols exhibited a bimodal distribution in the size ranges 0.4–0.6 μm and 5–6 μm. The chloride and sodium components exhibited by and large a unimodal distribution. The ammonium and sulphate components exhibited a bimodal distribution during the monsoon and a unimodal distribution during the winter. The nitrate component exhibited a bimodal distribution during the monsoon and winter. The molecular form of this component appears to be ammonium nitrate in the sub-micron range and sodium nitrate in the higher size range (1–10 μm)

94-GT-381 EFFECT OF INCIDENCE ON SECONDARY FLOWS IN A LINEAR TURBINE CASCADE

ABSTRACT The effect of incidence on the generation and growth of secondary flows in a linear turbine cascade was studied in the present investigations using

Pneumatic Radial Loading To Ease Preloading – An Innovative Technique

Soft ground improvement gained prominence all overthe world in view of ever growing engineering activities forvarious purposes. In view of serious problems during and afterconstruction in these deposits, vertical drains method usingpreloading is being frequently applied to improve these soil beds.However, in view of the difficulties associated with this technique,an alternative vacuum preloading technique was developed. Butvacuum preloading is also limited to the available atmosphericpressure with inevitable technical difficulties. The present paperdiscusses an innovative technique of applying radial pneumaticpressure with the help of inflatable balloons/tubes. The drainageis facilitated along the surface of inflatable tubes by providingfabric strips/the traditional strip drains. The laboratoryexperimentation in test tank indicated that this technique has thepotential for practical applications

Anchor Piled Footings – An Alternative Foundation Technique in Expansive Soils

A search for alternative foundation systems inexpansive soils has been continued since their problems wererecognized all over the world. Despite the availability of a goodnumber of remedial techniques, their adoptability andeffectiveness under varied geographical and climatic conditionshave remained questionable. The present paper discusses the fieldinvestigations on the recently promulgated technique of anchorpiled footings in expansive soils. These studies have revealed thatthe granular anchor piles exhibit promising pullout capacity evenunder fully wet condition compared to conventional concrete piles.The heave of model footings provided with granular anchor pilesdecreased by about 73-93% while for footings provided withconventional concrete piles the heave value is decreased by 40 -75%. It is felt from this study that the above technique of anchorpiled footings can be an effective alternative to conventional pilefoundations in expansive soils

Solar activity and Indian weather/climate

The literature on influences of solar activity on the Indian weather and climate is reviewed since the discovery of sunspot cycle. Fluctuations in solar activity are undoubtedly a factor affecting weather and climate. Although the results of some of the studies are conflicting, Indian weather and climate is, in general, inversely related to sunspots. However, the areal extent of floods in India seems to expand and contract in phase with the Hale double sunspot cycle, suggesting that the flood rhythm is in some manner controlled by long-term solar activity related to solar magnetic effects. All the evidences of solar influences on weather and climate may have practical implications in improving long-range forecasting of weather and climate, once the physical coupling mechanisms and their modification by other factors are clearly understood. Some of the promising plausible physical mechanisms for explaining solar effects on weather and climate are also discussed

Antihyperlipidemic activity of Chloroxylon swietenia in triton WR1339 induced hyperlipidemia

Background: Medicinal herbs are beneficial and effective either in the management and prevention of several metabolic disorders, associated with hyperlipidemia, hypertension and insulin resistance which increases the cardio-metabolic risk and demands for the life time therapy. Current allopathic medicines are expensive and reported with several adverse effects and hence, finding of a suitable herbal medicine for hyperlipidemic disorders is very important.Methods: Thirty albino rats weighing 200-230g were randomly divided into 5 groups were rendered hyperlipidemia with a single dose of triton WR 1339. Normal control, positive control, standard, aqueous and ethanolic extract groups were treated with tween-80, tween-80, atorvastatin, aqueous and ethanolic extracts of Chloroxylon swietenia respectively for seven days. At the end of the study, blood was collected for estimation of the lipid profile.Results: Both the aqueous and ethanolic extract groups significantly reduced the TG and VLDL levels.Conclusions: The extracts exhibited remarkable activity on one or either parameter of the lipid profile. It could be due to the presence of alkaloids, steroids, flavonoids, coumarins and phenols in the extracts