FREE VIBRATION ANALYSIS OF OUTRIGGER-BELT TRUSS SYSTEMS IN HIGH-RISE BUILDINGS USING LUMPED MASS SYSTEM

Framed tube system in tall buildings may be used with other systems to resist more effectively under lateral loads. The outrigger-belt truss system is a highly effective way of satisfying the motion constraints of tall and slender buildings. In this paper a simple hand-calculation methodusing lumped mass system is proposed for approximate free vibration analysis for combined system of framed tube, shear core and outrigger-belt truss systems in high-rise buildings. Building structure is discretized at each floor of building as a series of masses lumped at center of shear core. Each mass has single degree of freedom system. The effect of shear core and outrigger-belt truss on framed tube is considered as rotational spring at location of outrigger-belt truss system along the height of the structure. Using matrix eigenvalue problem, natural frequencies of free vibration are obtained. A 55 storey high-rise building installed with outrigger-belt truss system is analyzed for dynamic response. Then the results from the presented method are compared with those obtained using SAP2000 free vibration analysis. Differences between proposed method and finite element method are small. The proposed method is found to be simple and efficient, and provides reasonably accurate results in preliminary design stages of high-rise building structures.

کلیدواژه ها:

Outrigger-belt Truss ، Lumped Mass System ، Single Degree of Freedom ، Eigenvalue Problem ، Free Vibration ، Natural Frequencies