Mean signal of variable step signals

Hello, so, the problem is the following: I have 30 signals that go from 0 to 100 in time, but they are obtained from a simulation with variable time signal, so the timestep size is varying along each signal and among signals. I need to find the mean value of these signals. The porblem is thst first thing I tried to do is to use the minimum step size to interpolate all of them, so all of the are then the same size and is easy to fins the mean value. Proble: the minimum step size is way to small, and matlab deos not have enought memory to handle it. Is there anyway to compute the mean value keeping a variable step size? Lika taking the minimum stap size among the signals when necessary...but they are not coincident... Thank you beforehand