Natural frequency and damping ratio of steel plate–concrete walls with inclined studs under forced oscillation

The natural frequency and damping ratio of steel plate–concrete (SC) walls subjected to forced oscillation were analytically reviewed to determine the effects of stud shape and spacing on the behaviour of SC walls. Nine finite-element (FE) analyses were conducted considering different stud shapes and spacings. Shear-dominated (SC-S) and flexure-dominated (SC-M) FE models of SC walls were considered, and the non-linearity of the contact, the connection and the material properties were used. To verify the adequacy of the analytical model and the feasibility of the proposed analysis method, the results of laboratory experiments conducted by other researchers were compared with the analytical results. It was found that the damping ratio obtained from time history analyses showed an overall high value with the half-power bandwidth method and the lowest value with the fitted exponential curve method. For SC-S, for a load of half of the design strength, the damping ratio was approximately 3·0–4·2% while, for the design strength, it was approximately 4·1–5·2%. For SC-M, the ratios were 2·6–3·6% and 3·3–4·5%, respectively. When newly developed studs were used, the damping ratio was slightly reduced and the results for the two developed studs were not consistent. When the distance between studs was increased more than was necessary, the natural frequency reduced and the damping ratio increased.