def pipe_char_plastic_pressure(t, D, f_y, alpha_fab) ->'p_p':
    """Calculate characteristic plastic pressure p_p.
    Reference:
    DNVGL-ST-F101 (2017-12) 
        sec:5.4.4.2 eq:5.13 page:96 $p_p$
    """
    p_p = f_y * alpha_fab * (2 * t / D)
    return p_p
