ABSTRACT

The target of the present Diploma thesis is to perform a parametric study on steel

moment resisting frames, in order to obtain all the qualitative parameters that define their

inelastic response, under earthquake excitation. For this purpose, the steel frames are

subjected to Incremental Dynamic Analysis for a set of 8 real far-field ground motions. In

order to ensure a large and accurate database, an intense scaling was performed, with

respect to the PGA, ranging from 0.05 g to 6 g with a step of 0.05 g. The dynamic analyses

were performed using the OpenSEES software. Three case studies are examined. In the

first two cases, bilinear hysteretic model with 3% hardening was used, with and without

geometric nonlinearity, to evaluate the impact of second order effects on the response of

the frames. In the third case, a hysteretic model with cyclic degradation of strength and

stiffness was used, also taking into account P-D phenomena. The basic aim is to identify

the governing design parameter, for the particular frames, among those examined in this

study. Strength reduction and overstrength factors are examined with respect to global and

local ductility levels. Therefore, a performance based engineering approach is implemented

to this study, defining the performance level of each frame whenever these parameters are

calculated. Statistical tools have been used for increased accuracy and minimum error

margin. Furthermore, the collapse mechanisms of the frames are inspected, so as to

confirm the validity of yield and failure predictions according to each parameter on the

basis of the initial design. Programming techniques were implemented for the automation

of the whole process and the quality control of the obtained results. The analysis results

were afterwards used for the vulnerability assessment of the frames, comparing all three

cases studied herein. Finally, the vulnerability assessment results were used to predict the

direct financial loss within the scope of this study, in order to illustrate the practical

importance of the case studies.