S. Kumar

An evolutionary-degrading hysteretic model for thin-walled steel structures

An evolutionary-degrading hysteretic model is presented which can be used to simulate the seismic response of thin-walled steel structures. The degradation of strength and stiffness is related to the concept of the damage index. The damage index used, was developed to account for the various damaging effects observed in experiments, including the effect of the loading history. This enables the hysteretic model to simulate the response under a variety of loading histories. It is shown that the model is capable of simulating the various phenomena observed under cyclic loading. Finally, the model is used to simulate the pseudodynamic test results obtained by using earthquake accelerograms. Also the average values of the various parameters used in the simulation are presented for steel bridge piers of box section, designed according to the code of the Japan Road Association. These values, which are based on tests on a variety of specimens, can be used to develop the various inelastic response spectra for such piers.

Inelastic seismic design verification method for steel bridge piers using a damage index based hysteretic model

In order to ensure the safety of steel bridge piers against earthquakes, their inelastic response up to collapse needs to be predicted accurately. An evolutionary-degrading (E-D) hysteretic model was found to fulfill this need with very little computational effort. The model is based on a comprehensive damage index, which takes into account the effect of large deformation, low cycle fatigue and the nature of the loading history. Evaluation of the various structural parameters required to predict the seismic response of steel bridge piers is discussed and the formulas required are summarized. The accuracy of the method is illustrated by comparing the predicted response with that obtained from pseudodynamic tests using two accelerograms obtained from the Hyogoken-Nanbu earthquake of 17 January 1995 near Kobe City. The hysteretic model is then used to predict the response of four hypothetical piers designed according to the Japan Road Association (JRA) code and it is shown that the resulting damage is a function of the natural period of the pier.

ELECTROLESS PLATED NICKEL CONTACTS TO HYDROGENATED AMORPHOUS SILICON

Abstract We report for the first time investigations on electroless plated-nickel phosphorus alloy (Niue5f8) contacts to undoped amorphous silicon (a-Si:H). I–V characteristics of electroless Niue5f8P were compared with those of Nickel deposited by thermal evaporation. It was found that as-deposited Niue5f8P makes a rectifying contact to undoped a-Si:H. The effects of plasma annealing on the contacts were studied. Niue5f8P contacts on low pressure chemical vapour deposited a-Si are also reported here.