Limitations of a dynamic shear-frame model based in a small-scale experimental steel structure

Abstract

Many engineering problems require geometric modeling and mechanical simulation of structures. Through the structural models, engineers try to simulate the real behavior of these structures. It is important that a model contain all the necessary parameters that describe the structure and its behavior during its useful life. In the field of dynamics, one of the most used models is the shear-frame, in which the stiffness of the structure is given by the stiffness of the columns and the whole mass is concentrated in the floor levels, which are considered with infinite stiffness. In some cases, this simplification offers more conservative results, which can lead to considerable errors, especially in the case of natural frequencies. Knowing that the quality of a structural model depends on the simplifications considered, an experimental 3D steel frame, constructed to typify the dynamic behavior of a tall building, was tested with a data acquisition system and accelerometers, in order to obtain its natural frequencies. In addition, a numerical model was developed in order to ascertain the results. These values of natural frequencies are compared with an idealized shear-frame model obtained from the experimental model. This comparison allows a critical analysis of the numerical models that can be employed to represent the real dynamic behavior of structures. The aim of the investigation is to show the results of the modal analysis for each model, comparing them with the experimental results and commenting their advantages and the limitations.