A month before each winter and spring commencement, Point Loma Nazarene University begins preparing the Greek Amphitheatre for the nearly 12,000 visitors it’ll host over commencement weekend. Events Coordinator Kim Riddle and her team of contractors, Campus Facilities employees and the Records Department, estimate that four to five thousand people attend each graduation ceremony, with 400 graduates and faculty on the floor, 1,500 to 1,700 guests sitting in the white seats of the amphitheater and 2,000 to 3,000 additional family and friends in grandstands constructed for extra seating.
The temporary grandstands might seem spindly and unstable to some. So, in honor of the math foundational exploration course each undergraduate student has to take, let’s do a physics problem.
With the weight of 2,000 to 3,000 people sitting, how much force do they exert on the stands, and how does that compare to the building code weight allowance for bleachers?
First, we need to know how much the audience weighs. According to data from the Centers for Disease Control, the average American has a mass of 185.3 pounds, or 84.05 kilograms. Multiplying this by the rate of acceleration due to gravity, approximately 9.8 meters per second, we find our average American is exerting 823.7 Newtons of force on their seat, spread out over the area of their contact with the seat. For reference, a 1974 study on the physics of karate found that a concrete block can be broken with between 2,500 and 3,000 newtons of force in a concentrated area.
So, with our estimate of 2,500 guests, we can calculate that the crowd is collectively exerting about two million Newtons of force on the grandstands. But how does that compare to building code?
According to subsection 303.2 of the International Building Code, which the California Building Code is based on, “bleachers, folding and telescopic seating and grandstands shall be designed for a uniform live load of 100 pounds per square foot.”
That’s about 444 Newtons per square foot, so assuming each person has at least two square feet of area to sit, the grandstands are within code. In reality, Riddle estimates that each person has about three square feet of room, so guests at commencement are well within their weight tolerance.
In order to prepare for everyone, Events Services and Campus Facilities begin work on the Greek about a month before commencement. Riddle says this process starts with giving the Greek a bit of a tune-up.
“The Greek is very old, it’s one of the oldest amphitheaters around, and it’s made out of wood seating, so they’re constantly fixing it and doing things. We close the Greek down for about a month before just so they can fix the seating and paint [the seats], things like that,” said Riddle.
Then, two weeks out, the Statewide bleacher company brings in equipment and constructs the grandstands while Campus Facilities and Events Services start bringing in seating for the graduates and faculty, backdrops and banners. This year, Riddle says new ramps are brought in for disability accommodations and the lift is being tested.
The week before commencement is very busy. Flowers are hung by the Department of Grounds Maintenance and bunting is hung by Campus Facilities. The sound equipment company comes and sets up their equipment, and during the day on Friday the road is shut down.
“Campus Facilities will do the actual staging,” said Riddle. “Events Services are the people who move the tables and chairs around, but Grounds, a part of Campus Facilities, do all the flowers and get that ready, so Campus Facilities takes a really hefty load of getting it all ready. My job is just to make sure that all of those people are doing what they say they’re going to do.”
After working her job for nine years, alongside some employees of Campus Facilities who’ve been at PLNU for thirty years, Riddle said things are fine-tuned, and she can enjoy the graduation celebration and the joy that comes with the graduates’ accomplishments.
“It’s great and everyone’s smiling. That’s what we try to do, we try to make sure they’re having the best event that they can have, and for their family. They’ve finished! So, I think commencement is really a great time, it’s a long day for us but it all feels so good that it’s done and it’s done well, and we really try to make that event special for the students,” said Riddle.
Written By: Lily Damron
