MechSE Seniors Win Safety Design Contest

A retractable safety awning designed last spring by four MechSE seniors won second place in the 2009 Safety Products Student Design Challenge sponsored by the Safety and Protective Products Division of Industrial Fabrics Association International and the Narrow Fabrics Institute. The seniors, now alumni, designed and tested the retractable awning, which they built using a high-strength textile commonly used in bullet-proof vests, cut resistant gloves, yacht sails and hurricane protection curtains. Pound for pound, the fabric is 15 times as strong as steel, yet light enough to float on water. The design team's data indicated that the advanced fabric could provide protection from an 11 pound object falling from a height of 100 feet, protecting pedestrians outside high-rise buildings from falling ice and other objects.

Falling ice is a significant problem in cities like Chicago, where high rise buildings, cold temperatures, snow and ice can result in tragic and costly consequences. Several years ago, a man walking down the sidewalk on Chicago's Magnificent Mile was hit and killed by a large chunk of ice. His family sued the building owner and was awarded $4.5 million.

To prevent such tragedies and costly lawsuits, building owners now post signs that warn pedestrians of the danger. In extreme cases, the city may even close roads or walkways, which can create traffic problems. In Spring 2009, four MechSE seniors (Paul Ocampo, Evangelyn Reyes, Michael Sharlog and Richard Vucich) came up with a better solution.

To determine how well the fabric could protect people from ice and other falling objects, the students created a gravity-powered pendulum testing apparatus that allowed them to simulate the impacts of falling objects realistically and to predict how each fabric would respond when used in a protective awning. Although a gravity pendulum was safer, more repeatable and easier to construct than other testing methods, it had one key drawback. Its impact velocity was only a third what it would be for an object falling from a height of 100 feet. So, the team had to increase the mass of the impactor to make the kinetic energy equal to a 100-foot fall, or a drop from a 10-story building. They then verified the impact velocity using a high-speed camera that captured the time during the last inch of the pendulum's travel during impact.

After making sure that their apparatus was properly scaled, the students used it to test how much impact energy each of the six fabric samples they'd selected could withstand. The highest strength textile had 21 times the impact resistance of standard awning fabric. "Our data indicated that the advanced fabric could provide protection from an 11 pound object falling from a height of 100 feet," Sharlog said.

Additional research indicated that conventional awning frames are not designed to withstand the loads needed to protect people from falling objects. So, the student's proposed design called for the frame to be constructed from structural steel rather than the lightweight extruded aluminum or steel used in traditional awnings. Computer analysis of the frame design confirmed that the structural steel frame could withstand both weather and impact loads.

"Our results show that this product could not only protect pedestrians from falling objects in urban areas, but could also be useful at ski resorts, where rooftop snow and ice removal is a significant concern for up to five months each year," Vucich said.

Better yet, the awning took second place and $750 in the 2009 Safety Products Student Design Challenge. Industry judges were impressed with their analysis of the problem and their solution to "as safety issue all of us who live in norther cities see where high-rise buildings exist."