mass /stiffness proportional damping type .Manual is confusing and unlikne LRB type ,there is no prepared video/webinar or resource for this.The main confusion is as a result of linear parameters and nonlinear parameters availability at the same time,user can not decide about the procedure .most of the time program takes linear parameters instead of nonlinear parameters and this cause to shift from nonlinear analysis to linear one.we can not clearly choose nonlinear parameters to go on with that.This area need some extra explanation and resources provided for users