| dc.description.abstract | A suite of beam-column element formulations have been developed for assessment ofthe nonlinear response of structures under earthquake loading. They range from simpleconcentrated inelasticity elements, to the more advanced distributed inelasticity fiber elements.Research and development of new sophisticated models have been, and stillare, of great interest, as rising computational power and technology has allowed evenfaster numerical calculations. Despite the increase of new and improved formulations,the elements in commonly used finite element software are prone to produce significantinaccuracies in their approximations of nonlinear structural response. This happens particularlyfor beam-column members experiencing strain-softening behaviour, which iscommon for columns with large vertical loading. The phenomena is called localization,and is due to inelastic deformations localizing in concentrated parts of a structural member.It brings with it the numerical disadvantage of non-objectivity, which means that thestructural response differs depending on the discretization of elements and integrationpoints.This thesis makes a review of the commonly known inelastic beam-column elementformulations with a focus on their advantages and disadvantages. These include thedisplacement-based and force-based distributed inelasticity formulations, concentratedinelasticity elements with springs at member ends, as well as the more sophisticatedconcentrated inelasticity elements with fiber discretization. Localization issues are presented;first the physical definition, which is observed on testing specimen of concretecolumns, and second the numerical definition. Different regularization procedures toprevent numerical localization have been assessed, and a comprehensive verifying analysishas been performed with the use of OpenSees.Finally, the beam-column element formulations are applied in the modelling of a onestoryframe, which has been pseudo-dynamically tested in a laboratory. This is done inSeismoStruct, where the element discretization properties have been determined basedon the results from the OpenSees analysis. Then, a numerical comparison between experimentaland analysis results have been made. Conclusions on the application of thedifferent elements have been drawn based on these results. The analysis of the one-storyframe succeded in portraying the characteristics of the discussed element formulations,thus verifying their capabilities of modeling structures subjected to strong lateral forces. | nb_NO |
