Forty years ago (July 17, 1981) two of three atrium-spanning ‘skywalks’ at the Hyatt Regency Hotel in Kansas City, Missouri, collapsed onto a crowded dance event, resulting in 114 deaths and 216 people injured. The hotel had been open for one year. The skywalks design called for a fourth-floor span 120 feet long, a third-floor span of the same length, offset to one side, and a second-floor span directly under the top span. Each walkway weighed about 64,000 pounds. The walkways were was suspended from the roof of the building by three pairs of steel rods, each 1.25 inches in diameter, attached to steel beams that crossed under the walkways.
|To right, the 4th and 2nd floor skywalks, fallen|
to the atrium floor. The bottom of the 3rd floor
skywalk is top, center. Click to enlarge photos.
Did the roof collapse? Did the rods pull out at the top? Did the rods break? No, no, and no. Months of investigation concluded that the structural failure was a consequence of a cascade of human errors. The architect’s original design called for rods to pass through three steel cross-beams supporting the upper skywalk and continue to cross-beams underneath the lower skywalk. For each skywalk, nuts threaded on the rods would be under the beams, the full weight of the skywalk supported by these nuts. The company contracted to manufacture the rods objected. For nuts to be in place under the upper skywalk beams meant that the entire length of the rod from the end supporting the lower skywalk all the way to the upper skywalk would need to be threaded, so the nuts at the upper level could be rotated up the rods from the bottom.
|Right side image shows what |
was actually built. Center image
shows the welds.
This horrific flaw was compounded by the fact that the design of the cross-beams had also been changed. For each cross-beam, two pieces, each shaped like a squared-off letter “C” were designed to be welded to each other along the edges, creating a rectangle. The design call for the welds to be on the sides, so that the holes drilled for the support rods would go through solid metal. Instead, the rectangular cross-beams were set under the skywalks with the welds on top and bottom, so that the drilled holes went through the welds. The collapse came when the upper beams separated at the weld line, allowing the nuts to slip through, leaving the upper rods still firmly attached to the roof. Lawsuits were filed. Court reports stated that in the process of going from initial design to completed construction, architects and engineers each believed that someone else had performed safety calculations. As there was no formal review process to track all changes, this never happened.
Has Maynard’s history been marred by any construction design flaws that led to a catastrophic event? There has been a slew of building fires, but there is no reason to believe that causes were other than mishaps with wood stoves, coal stoves, kerosene lamps and candles (or arson, at least two, likely more). There are mentions of bridges being destroyed by floods, but those were natural disasters.
The 105-year history of gunpowder manufacture at American Powder Mills, located on the Maynard/Acton border on both sides of Route 62, was marred by explosive disasters. In fact, between 1835 and 1943, there were at least 26 explosions, 30 deaths. Newspaper reports mention windows broken in Maynard, explosions heard in Concord, and workers’ body parts being collected in buckets (funerals were closed-casket). The salient point about gunpowder manufacture was that explosions were a given, so by design, the plan was to minimize damage.
|Click to enlarge. The wheels would rotate and the |
dish they were suspended above would revolve,
to mix the dampened ingredients. Too dry, or if
the stone wheel created a spark if it touched the
dish, and there would be an explosion.
The black powder manufacturing process in brief: potassium nitrate, sulfur and charcoal are each milled separately to a fine powder then mixed together while dampened with water. The blend is pressed to remove water, the presscake then broken into the desired coarseness in the kernel house (coarse for cannons, fine for guns), sieved to remove dust, resulting grains glazed with graphite to prevent sticking in humid air, further dried, and then packed into copper-nailed oak barrels or tin containers. Workers considered the kernel-house the most dangerous, the drying-house next.
|Shattered beams and bent iron rods from when an|
explosion had destroyed a building. The 2,000
pound grinding wheel was blown yards away.
The remnants of a building pictured to the left can be seen along a path that starts at the canoe launch area located on the south side of Route 62.