Armin PRACKWIESER

Influence of different modeling strategies and parameter variations on the prediction of the seismic response of elastoplastic frame structures

 

The seismic load-bearing capacity of buildings depends on many factors. The seismic load as well as the structure itself plays a highly important role. In this respect on primary goal of earthquake engineering is to check the stability of a building in case of a severe seismic event. The assessment of seismic induced global structural collapse requires a high computational effort that depends on the selected numerical model. The adequate model should provide the desired results with low calculation effort.

This Master’s thesis investigates different types of mechanical models and their properties to approximate the seismic response of real elastoplastic structures. The frame properties are varied and the effects on the seismic collapse capacity are analyzed via static and dynamic methods of analysis. The first part describes these methods as well as their theoretical background. Subsequently, simple models such as the single-degree-of-freedom system but also generic frame models with a higher complexity are investigated. Model properties and their advantages and disadvantages are discussed. The procedure of generation of the frame models is specified and shown in an example. All considered models are more or less vulnerable to the P-delta effect. The next part concerns the implementation of the models and analysis methods in an opensource Earthquake Engineering Simulation Software (OpenSees). Significant parts of the code are presented and explained. Then, the influence of different frame parameters such as number of stories, payload, mass distribution, damping-methods and member-models on the results is discussed. Pushover analysis performed with and without the consideration of gravity loads. The frame behavior, but also the internal forces of frame components such as beam, column and springs, is investigated trough dynamic time history analysis. In the final part of the thesis a summary of the results and a prospect to further investigations is provided.

 

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