Seismic response of tall guyed masts to asynchronous multiple-support and vertical ground motions

The seismic behavior of tall masts was investigated with special considerations for the realistic modeling of ground motion at the supports. Three existing masts with varying heights of 213, 313, and 607 m were numerically studied under the effects of three earthquake records with all three translational ground motion components. The earthquake excitation was prescribed as a displacement-controlled motion providing the opportunity to consider the asynchronous shaking of the cable ground anchors and mast base. This effect was studied by varying the shear wave velocity of the traveling wave corresponding to different degrees of soil stiffness and observing the general trends of selected response indicators. The three towers showed sensitivity to asynchronous shaking of their ground supports. More severe structural response was obtained for softer soil conditions, and the 607 m mast showed sensitivity even for relatively stiff soils. The effects of considering or excluding the structural damping and the vertical component of ground motion were also separately investigated and both factors were found to affect the response indicators significantly.