REPLACE_WITH_DASH_DASH
        function this = evalForce(this,int)
            % Needed properties
            dir  = int.kinemat.dir_n;
            ovlp = int.kinemat.ovlp_n;
            vel  = int.kinemat.vel_n;
            res  = this.residue;
            kl   = this.stiff;
            ku   = this.unload_stiff;
            
            % Elastic force according to loading or unloading behavior
            if (vel > 0) % loading
                f = kl * ovlp;
            elseif (vel < 0 && ovlp > res) % u