1st Croatian Conference on Earthquake Engineering 1CroCEE 2021

As the development of the codes of practice converges towards limiting displacements rather than forces, it is of utmost importance to be able to design the structures for predefined performance criteria. Following the objective-based design, one can accurately predict the structural displacements during realistic earthquake loading and evaluate the response of the structural elements. The main idea of this study is to demonstrate an improved methodology for design and assessment of steel moment resisting frames subjected to loading from recorded ground acceleration. Namely, material degradation model is used to model plastic hinges in the beams of the frame in order to realistically capture the behavior of the steel during earthquake. Additionally, the same frame is developed with a typical distributed plasticity model in order to validate and to prove the necessity of the improved method.
Firstly, the design of the frame according to the current codes of practice is performed. Then, the performance objectives of the analysis are defined and the various limits in the existing literature are considered. In order to perform the nonlinear time history (NLTH) analysis, modelling of the two types of frames in a suitable software is conducted. Prior to that, case study for model calibration and verification is performed and the results obtained are used for the setup of parameters for NLTH analysis. The NLTH analysis is done after the selection of a reliable set of recorded ground motions.
Hence, the performance-based assessment of the steel moment resisting frames is conducted and several demand parameters are recorded. Since the moment resisting frames are the most ductile type of steel structural configurations, they exhibit very large deflections before the structural damage occurs. Therefore, the inter-story drift ratios and residual drifts are measured and their compliance with the existing codes is compared. In the end, conclusions regarding the behavior of the moment resisting frames subjected to realistic earthquake loading are drawn and suggestions for improvements in the design are presented.