The spatial correlation matrix of the load is defined as follows. Let ${F}_{\left(N,i\right)}^{I}$ be the load applied to degree of freedom i at node N in load case I, through the use of a concentrated or distributed load. Let J correspond to the Jth frequency function referenced under load case I. The spatial correlation matrix used in the random response analysis for this load case is then

$${\mathrm{\Psi}}_{\left(N,i\right)\left(M,j\right)}^{IJ}={C}_{\left(N,i\right)\left(M,j\right)}^{IJ}{F}_{\left(N,i\right)}^{I}{F}_{\left(M,j\right)}^{I},$$

where ${C}_{\left(N,i\right)\left(M,j\right)}^{IJ}$ are the coefficients defined in user subroutine UCORR. Typically the load magnitude is given as 1.0; therefore, the load definition is simply selecting the nonzero terms that will appear in ${\mathrm{\Psi}}_{\left(N,i\right)\left(M,j\right)}^{IJ}$.