def hyperbolic_load(y, pu, a, b):
    """
    Static hyperbolic model developed by Lee
    
    Parameters
    ----------------
    y -- displacement
    pu -- ultimate load
    a, b -- coefficients
    
    Output
    ----------------
    p -- soil resistence pressure
    """
    p = y / (a + b * y) * pu
    return p
