#### Description

This paper describes a computer program developed for

structural dynamic analysis of horizontal axis wind

turbines (HAWTs). It is based on the finite element

method through its reliance on NASTRAN for the development of mass, stiffness, and damping matrices of

the tower and rotor, which are treated in NASTRAN as

separate structures. The tower is modeled in a stationary frame and the rotor in one rotating at a

constant angular velocity. The two structures are

subsequently joined together (external to NASTRAN)

using a time—dependent transformation consistent with

the hub configuration. Aerodynamic loads are computed

with an established flow model based on strip theory.

Aeroelastic effects are included by incorporating the

local velocity and twisting deformation of the blade

in the load computation. The turbulent nature of the

wind, both in space and time, is modeled by adding in

stochastic wind increments. The resulting equations

of motion are solved in the time domain using the

implicit Newmark—Beta integrator. Preliminary

comparisons with data from the Boeing/NASA MOD2 HAWT

indicate that the code is capable of accurately and

efficiently predicting the response of HAWTs driven

by turbulent winds.