Stiffness Matrices, Second-Order Effects, and Influence Coefficients

For structures with linearly elastic material behavior, structural, and dynamic analyses can be performed by using stiffness matrices and accounting as necessary for second‐order effects. Influence coefficients, representing wind effects of interest induced by unit loads acting at mass centers along the structure's principal axes, and unit torsional moments about the centers of mass are considered. Stiffness matrices, geometric stiffness matrices, and influence coefficients can be determined by using finite element software. Second‐order effects can be determined by a variety of methods other than the geometric stiffness matrix method, including the simple moment amplification method. Influence coefficients are used in conjunction with wind and gravity loads acting on the structure to determine internal forces, displacements, and accelerations induced by those loads. For any specified wind speed and direction, the wind load time series are computed from time histories of pressure coefficients.