Level of Detail Required to Model Special Steel Moment Frames to Evaluate Floor Accelerations in Nonstructural Components

The floor acceleration response of special steel moment frames (SMF) subjected to earthquakes has been evaluated by multiple investigations. It has been demonstrated that peak floor accelerations and floor spectra, which are the most evaluated responses, are reduced when inelasticity is included in the mathematical model. However, the amount of detail required by the model to evaluate floor accelerations in nonstructural components has not been assessed. In this study four different models are used to compute the peak floor accelerations and the floor spectra of an 8-story special steel moment frame. The first model includes concentrated inelasticities and has been used to evaluate the collapse performance of SMFs, thus making it the most detailed model since the constitutive laws incorporate strength and stiffness deterioration. The second model also has concentrated inelasticities, but with a simple elasto-plastic behavior, therefore no degradation is included. The third model was created using fibers with displacement-based elements and a material that does not include any degradation. The last model to be analyzed does not include any inelasticity. All the mathematical models are analyzed to obtain the floor acceleration responses under design level ground motions. The results show that all the methods are accurate enough to be used to evaluate the accelerations in nonstructural components at design level earthquakes.