Generally, in order for us to be able to help you need to report the entire error message that you receive, everything in red. Additionally we would need to see your function call and function definitions.
However, there are some obvious programming errors here. You declare some symbolic variables. Don't do that. You don't need them. Most likely, symbolic variables are variables that you want to optimize. They should be the variables in your d vector.
Also, you need to write a separate function for your nonlinear constraints. Something like this:
function [c,ceq] = confun(d)
c = Ps_sample - ((6*Pf_sample*l/b*h^2).^2 + (Pt_sample/h*b^2*(3+1.8*b/h)).^2).^0.5;
MATLAB mathematical toolbox documentation