Structural Dynamic Modelling of a Multi-Storey Shear Frame using Mass and Stiffness Addition

Designers of systems involved in high-speed operation and users of lightweight structures have realised that measurement of stress/strain properties are not sufficient and that dynamic measurement / analysis are necessary for a comprehensive understanding of the characteristics. The shear frame structure was modelled using solid elements (ANSYS solid 187) and the discrepancy between the experimental and initial numerical results were very high. The three experimental modes were observe and the suspected areas of local stiffness were noted; these being the areas of connection between the floor plates and vertical pillars and ANSYS shell 181 was used to adjust the stiffness locally. Also with appropriate engineering judgements, omitted masses compared with the physical structure were added locally using ANSYS mass 21 element type. In addition, the finite element model boundary conditions were carefully manipulated to predict the experiment condition. This technique of updating proved to be very successful as the mix-match between the experimental and finite element results were reduced.