In areas with seismic activity, the tops of risers exceeding 3'-0" in length shall be provided with which brace?

In areas with seismic activity, the tops of risers exceeding 3'-0" in length shall be provided with which brace?

• A. 2 way brace
• B. 3 way sway brace
• C. 4 way sway brace
• D. No brace

Answer: (C)

In seismic areas, long vertical risers can sway in multiple directions during an earthquake, so they need strong top restraint to prevent movement that could cause misalignment or failure. A four-way sway brace provides restraint around the riser in all directions, tying it into the structure at four points and stopping both horizontal sweeps and rotation at the top. Since the criterion applies to risers longer than 3 feet, this maximum level of restraint is required to keep the long riser stable under seismic forces. A two-way brace would limit restraint to one plane, and a three-way brace offers less protection than a four-way brace, while no brace leaves the riser unrestrained.

In seismic areas, long vertical risers can sway in multiple directions during an earthquake, so they need strong top restraint to prevent movement that could cause misalignment or failure. A four-way sway brace provides restraint around the riser in all directions, tying it into the structure at four points and stopping both horizontal sweeps and rotation at the top. Since the criterion applies to risers longer than 3 feet, this maximum level of restraint is required to keep the long riser stable under seismic forces. A two-way brace would limit restraint to one plane, and a three-way brace offers less protection than a four-way brace, while no brace leaves the riser unrestrained.