Structural health monitoring (SHM) techniques have previously been proposed based on structural intensity (SI) due to its sensitivity to changes in boundary and loading conditions, and impedance, as well as to various damage mechanisms. In this paper, computational techniques for SI-based SHM are presented. Finite element solvers combined with SI equations can yield intensity maps over structures to determine characteristic changes in power flow due to damage. Numerical techniques for structural surface intensity (SSI) are also introduced using two alternative methods: A time domain approach that directly uses SSI equations that are valid at the surface of any elastic solid, and a frequency domain technique, which computes SI for very thin plate elements located at the surface of the structure. Advanced contact features such as nonlinearity can also be included in the model to increase the damage detection sensitivity. A plate model is used to illustrate these capabilities using SSI maps at nonlinear harmonics (NSSI). The results show both improved damage sensitivity and more global detection capabilities in a NSSI-based SHM system. A complex structure is also included to show global and local changes in SSI due simulated damage scenario. The techniques developed can be applied to general SI/SSI assessments and the design of SI-based SHM systems.