By Mary Kate McGowan, Associate Editor, News
About every three years, an earthquake that is strong enough to be damaging hits Nevada and eastern California, according to the Nevada Seismological Laboratory.
But when Scott Campbell, Ph.D., P.E., Member ASHRAE, visited Las Vegas, Nevada, a few years ago, he noticed a new building did not have any seismic restraints on its HVAC equipment, even though it is located in a fairly high seismic zone.
“It got through all these inspections,” he said.
In the event of an earthquake, the lack of restraint on the equipment could be deadly.
While not every region deals with seismic concerns, most areas have to keep wind considerations in mind. But sometimes code officials, contractors and others who work on projects are not vigilant and the seismic and wind restraints necessary for buildings in high wind and earthquake-prone locations “slip through the cracks,” he said.
“Wind is a concern everywhere, and seismic is a concern probably in more parts of the country than you think,” said Campbell, who works at the Portland Cement Association.
At the 2018 ASHRAE Winter Conference in Chicago, Campbell discussed industry and ASHRAE resources that help building professionals accurately fulfill seismic and wind restraint of HVAC equipment in his presentation, “Overview (FEMA) of Best Practices and Industry Recommendations.”
Campbell said the industry’s best practices are found in the published standards on seismic and wind restraints, and it boils down to having someone qualified doing the calculations on each project to determine the anchorage required for the equipment based on the equipment’s loads and other factors.
“The main issue in meeting the codes is anchoring your equipment properly, whether it’s mounted to the floor or it’s ceiling–mounted,” he said.
Anchorage requires specific calculations for every job, Campbell said.
Depending on where the equipment is located, anchorage includes different factors. If it is mounted overhead, the equipment pulls on the anchor during whatever wind or seismic load occurs, and if the equipment is mounted on the floor, it matters if it is located near the edge of a concrete slab, he said.
SEISMIC CONCERNS
In areas with seismic concerns, calculations include the weight of the equipment, the type of equipment and the importance of the equipment.
Some equipment is more flexible than others, he said. Equipment such as air-handling units and fans tend to be more flexible, while equipment that deals with liquids such as chillers and pumps tend to be more rigid because of the requirements for containing liquid, he said.
“In some cases you have to look at whether the equipment would be functional after an earthquake,” Campbell said.
There are industry standards and guidelines for certifying your equipment as well as ASHRAE Standard 171–2017, Method of Testing for Rating Seismic and Wind Restraints.
Hospitals, emergency shelters and schools are just some examples of buildings where HVAC systems might have to be operational during and after an event, he said.
To reduce seismic loads on the equipment, the closer to the ground the equipment is located, the better, he said. Generally, housing the equipment on the bottom floor is not practical, and the equipment’s restraints and anchorage must be calculated keeping the seismic forces in mind.
“What tends to happen in an earthquake is the building moves, and that amplifies the motion. So the higher up in the building you are, the higher the forces are for seismic,” Campbell said.
WIND CONCERNS
In areas with wind concerns, Campbell said anchorage calculations revolve around the equipment’s exposure to the wind. If a piece of equipment is inside a building, the wind load is not a concern, but if it is on the roof, the equipment’s surface area and the parts of the equipment that is exposed to the wind should be taken into consideration.
Typically, it is best to design for the worst case and eliminate the wind exposure if possible, according to Campbell. To reduce wind exposure, sometimes screens are installed around the equipment for protection, he said, but their effectiveness can be limited depending on the design.
“For wind, the higher you are, the stronger the winds are in any location. They’re lowest at the ground level,” he said.
How high the equipment is located in the building is not as much of a concern for high-wind prone buildings, he said. The bigger concern is if the equipment is located inside or outside the building.
RESILIENCE
Places such as the U.S. West Coast and Japan are known to have high seismic activity and have plans in place to mitigate the threat, but other places that are prone to the disruption are not as prepared, Campbell said.
Seismic threats to buildings’ HVAC systems are more or less ignored in some areas, he said, unless contractors and code officials are vigilant.
“There are parts of the country where if no one catches it, they don’t do anything at all,” he said.
In some places, seismic and wind restraints are required by code, he said. But engineers still need to pay attention to the specific area in question to determine if it is a high seismic activity zone, or if the building in question has specific needs like remaining operational during and after an event, he said.
“There’s a lot of movement now looking at resilience to have a lot more buildings designed to a higher standard. So instead of just not killing anyone, the building is actually functional at some level after a major event,” Campbell said.
To install equipment properly and in the right area, Campbell suggested involving the people who are doing a building’s seismic and wind design as soon as possible.