Tower Response to Actual and Simulated Wind Forces

The mathematical model of the tower, with the flexibility coefficients derived by assuming an idealized space truss and with masses between midheights of panels being concentrated at the panel points, is reasonable and adequate. The assumptions of uncoupled motions in the orthogonal horizontal directions and a rigid foundation are valid for the mathematical model of the tower on the basis of experimental data. Previous studies showed that three modes are adequate for dynamic analysis of free-standing towers. For free-standing structures such as the tower used for this study, the fundamental mode of vibration predominates. Experimentally determined natural periods of vibration compare very favorably with the predicted values for both horizontal directions. The structure has a fairly low damping ratio for the fundamental mode of vibration.