using type TrussFEACrossSec{Float64} with TrussSolver

From my inspection, the type `TrussFEACrossSec{Float64}` is only used the generate the problem. 
But it's not usable in any other format? 
i.e. 
You can't do add (+) or subtract it with numbers 
`TrussFEACrossSec{Float64}(1.0) `+ 1 gives an error

I want to use it with `TrussSolver(solver)(<input a vector of areas>` 
