Based on the provided detail of a Special Moment Frame (SMF) beam-column joint, what is the length of the critical plastic hinge zone where closely spaced transverse reinforcement (hoops) must be provided?

• 1.5 times the beam depth (1.5h)
• 3 times the beam depth (3h)
• 2 times the beam depth (2h)
• The clear span of the beam divided by 4 (L/4)