What Went Wrong > Miami Herald, December 20, 1992 > Page 3 : 無料・フリー素材/写真
What Went Wrong > Miami Herald, December 20, 1992 > Page 3 / danxoneil
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| 説明 | Text continued from Page 2SRSPECIAL REPORT: WHAT WENT WRONGFAILURE OF DESIGN AND DISCIPLINEJEFF LEEN, STEPHEN K. DOIG and LISA GETTER Herald Staff WritersSection: SPECIAL SECTIONEdition: FINALPage: 3SR-- lasting up to 15 or 20 seconds and cutting tiny swaths roughly 50 feet wide and 200 feet long."We don't want people to think that the whole area was swept by 175 mile per hour winds," Black said. "It's just in the streaks where you get winds that high."From the peak wind, scientists like Black are able to calculate an equivalent maximum sustained wind in Naranja Lakes of above 133 miles per hour. A fatal design flaw compounded the wind's havoc for much of Naranja Lakes: missing were vertical steel rods that would have greatly strengthened hundreds of concrete-block condo units.Another of the high-damage areas, the section off Old Cutler Road, was near the high point of the 16-foot storm surge that hit Dade County, where the storm's winds hit South Florida's coastline with their greatest energy. The highest confirmed wind reading occurred here -- 177 mph for 2.5 seconds -- just before the anemometer atop a 33-foot pole collapsed at a private home near SW 162 Street and 85th Court.The Old Cutler Road area, like most of the region in the storm's eyewall path -- the swath of South Florida that took the hardest hit -- was rated F-1, peak winds up to 151 mph and sustained winds equivalent to 97 to 114 mph.COUNTRY WALKWhy was Country Walk devastated, while some nearby homes weren't?But in devastated Country Walk, the winds were even weaker, rated F-0 by the scientists: sustained from 64 to 96 and gusts to 127 mph.Yet here the damage was the second greatest of any area in South Dade, according to the computer analysis.Why?Some residents looked at Country Walk after the storm and immediately thought the houses, nearly all of which had extensive roof damage, had been hit by tornadoes. But the NOAA scientists, who are experts at spotting the paths of tornadoes in wreckage, found no such evidence."In a tornado, these kind of houses would just be flattened," Black said. "If there had been any tornado features here, you would see some kind of departure, some curvature to the debris paths. What you should be able to see is a curved path of destruction, and the debris from the houses flung out at an angle from the wind."Since Country Walk is largely a collection of wood-frame houses, some have speculated that the destruction there came, if not from a tornado, then from hard wind hitting weak wood.The NOAA scientists who visited Country Walk did not see any evidence of extremely high wind like the streaks that devastated Naranja Lakes, though an unconfirmed anemometer report of 144 miles per hour did emerge from the area after the storm.Black carefully studied an aerial photograph of Country Walk and estimated the peak winds at no higher than 100 to 110."There are some older Florida-style houses in that area out there that are just as exposed as Country Walk," Black said. "And they're not totally devastated like Country Walk was."The Herald hired an engineer, Eugenio Santiago, to inspect four houses in Country Walk. He found them especially ill- equipped to fight off the hurricane. The weak point was the "storm bracing" -- two-by-fours that strengthen the gable ends, the sides at either end of a pitched roof that provide an extremely exposed flat face to the wind.A chronic lack of bracing allowed head-on and suction winds to rip apart the towering gable ends in Country Walk. The few braces found were often sloppily attached. Entire rows of nails missed trusses on the roofs.Despite mounting evidence of structural weakness, others continue to blame the wind. They point to the severe damage to Homestead Air Force Base and the Turkey Point nuclear power plant, as well as the reinforced concrete utility poles that broke in the storm."In some cases, the wind was so bad, even if the house was built perfectly it would be the same result," said Roberto Pineiro, Dade's chief building inspector. "You see outside Country Walk huge Florida Power & Light poles snapped in half. That's reality. That's for everyone to see."But tall and slender light poles are exposed to higher winds than houses, and they lack the ability to efficiently distribute wind forces throughout their structure, like houses do.MAKING HOUSES SOLIDStudy: Materials to strengthen houses would have cost $200 to $300Built correctly, lower-profile houses can resist high wind forces, as box-like concrete-block-style 1960-era houses demonstrated all over South Dade after Andrew."What you've got to do is transmit those forces into the ground," said Crane Miller, a Washington lawyer who did a study of Hurricane Hugo for NOAA. "The only way to do it is to make sure everything is tied securely together. It is easy."To me, the catastrophe is the materials you would need to strengthen those houses would have cost about $200 to $300 per building and are insignificant in the total capital cost."The Air Force base and Turkey Point also have much higher wind profiles than houses. And they were exposed to the full force of unobstructed winds along the coastline.Most houses further inland faced weaker winds because wind generates friction and slows down after it hits land. Open fields and lakes might allow the wind to speed up a bit, but trees slow it down."Having trees in the neighborhood creates a little boundary layer," Black said. "It's like having a shock absorber for the wind."Country Walk was perched at the edge of open fields, but it was also thick with trees. And the computer analysis shows that the interior areas of Country Walk fared just as badly as the edges that were more exposed to the wind.Some comparisons are worthwhile to put Country Walk in context.In the computer analysis, 18 Country Walk subdivisions and condos encompassing 936 units were rated 98.2 percent uninhabitable with 90 percent of the inspections completed. South Miami Heights Manor, a subdivision of 765 concrete-block houses built in the early 1960s, was only 2.5 percent uninhabitable with 68 percent inspected. And the NOAA scientist rated the wind higher in South Miami Heights.Another comparison lies in the number of destroyed houses per subdivision. A house was rated destroyed if the damage was so extensive that the remnants had to be bulldozed and the house totally rebuilt.The two-square-mile area containing Naranja Lakes, an area known as "Ground Zero" centered roughly on Southwest 280th Street and 145th Avenue, had the most destroyed houses -- 368.The square mile containing most of Country Walk had 70 destroyed houses -- by far the most of any area north of Southwest 260th Street.South Miami Heights Manor had six.The large uninhabitable area off Old Cutler Road, where the homes were built in the early 1970s and are assessed at about $170,000, had only three destroyed houses.NARANJA LAKES3 died here, but damage was much lighter at nearby Sunny HavenNaranja Lakes had by far the worst damage of any area in South Dade. It was the site of both the worst wind and perhaps the worst design flaw, according to an engineer hired by The Herald to study the hurricane damage.Naranja Lakes was built in the early 1970s by a Mafia- associated builder who put up concrete-block condominiums with large, overhanging flat roofs. The one-ton concrete tie- beams that braced the walls and connected the roofs to the houses were not anchored to the foundation by vertical steel rods.The result: the normally wind-resistant concrete-box design became a deathtrap. When the wind streaks hit Naranja Lakes, the roofs took off, tie beams in tow, like flying wings. Three people died as the heavy beams toppled walls and drove through roofs like giant javelins.One subdivision near Naranja Lakes fared much better: Sunny Haven, a late-1950s development of 99 houses with an average assessed value of $29,000. Barely 1,000 feet from the utter devastation of Ground Zero, Sunny Haven rated only 26 percent uninhabitable."They're all very small houses with pitches about what they're supposed to be in Dade County, as opposed to the large, flat roofs of Naranja Lakes," Black said. "I don't see any reason why those places didn't experience the same kind of winds that Naranja Lakes did."Black, the NOAA scientest, has studied several concrete- block houses that lost their roofs and tie-beams in similar ways during Andrew. The common link: none had vertical steel holding the tie-beams down."All the houses that I've looked at that were destroyed had that problem," Black said. "It appears that no matter how high these winds were, a lot of these houses would have survived if they had these vertical columns."County-wide, flying concrete tie-beams were a relatively small problem, restricted to Naranja Lakes and a few isolated areas.The bigger problems were the smaller-scale failures that proliferated in Country Walk and other neighborhoods in weaker winds zones: garage and double doors that blew in and staples and gables that gave way."Those shingles are stapled on with a staple that didn't hold," said Marks, the engineer. "The felt that was stapled on didn't hold. The (particle board) and the plywood didn't hold."When the shingles, felt and particle board or plywood went, the roof went. When the roof went, the house became uninhabitable. And the high-pitched gable ends that were all the architectural rage in the 1980s helped the roofs go."The lack of understanding of how to build a gable caused as much damage as the staple problem," Marks said.At the heart of the roof failures was confusion among truss manufacturers, architects and contractors about who was responsible for the complex engineering involved in bracing the gable ends."If you look at the building code, it's deficient," Dade Building and Zoning Chief Carlos Bonzon said. "It's not clear who's responsible. The engineer for the truss manufacturer or the architect of record?"Bonzon admitted that his building inspectors had to rely on the contractors to build the gable ends correctly because the inspectors "didn't have training in wind-resistant construction. There is a deficiency in all levels in wind-resistant construction."UNMISTAKABLE LESSONScientist: Damage was 'proportional to the kind of construction used'The Country Walk area provides one of the starkest contrasts in the entire hurricane-ravaged landscape. Seen from an aerial photograph, like the one on the cover of this special section, the lesson is unmistakable. The aerial shows five neighborhoods, all constructed differently."The damage is directly proportional to the kind of construction used," said Black. "It was astounding for me to see that."The northernmost neighborhood in the photograph, Country Walk Section 2, was the hardest hit area of Country Walk. The 184-home development, built in the early 1980s, had 100 percent of its inspected homes rated uninhabitable and 33 houses destroyed.But the destruction immediately south of it was even worse. Here, the Dadeland Mobile Home Park, was a shredded mass of total devastation.Next to the park, Roger Homes, a 38-home development put up in the late 1980s, was also heavily damaged, 100 percent uninhabitable.Below the park, Mediterranea, a 111-home subdivision built in the late 1980s, was rated 99 percent uninhabitable. It did poorly, but not quite as badly as Country Walk.Next to Mediterranea and about a third of a mile south of Country Walk sits a success story: The 71-home Munne Estates project, built in 1989 and 1990.The red-tiled-roofed, concrete block houses look almost pristine in the aerial photograph."Maybe the storm went around my project," said Raul Munne, 51. "Either that or we did something right."He did a lot right. In stunning contrast with the surrounding subdivisions, nearly all of the roofs held on the $80,000 to $95,000 Munne homes. Munne built his roofs with plywood, not the weaker particle board, and he used thicker plywood than the code allowed. Then he used nails driven in by hand, not staples, to hold it down."Munne should definitely get credit for building good houses," said Dawn Mareno, a resident of Munne Estates. "All we lost were tiles."LONG DRY SPELLAvino: Long spell between storms helped foster complacencyHow did things get so bad that homes built with pride and craftsmanship can become a cause for celebration -- instead of the rightful expectation of any home buyer?Many blame the long dry spell between serious hurricanes in South Florida. By the 1980s, builders could put up houses with no memory of what it is like to be tested by 120 mile per hour winds."I think people got very complacent," said Santiago, the veteran engineer hired by The Herald. "People were justoblivious to things, as if they thought we never were going to have a hurricane in this area.""Without a doubt, complacency plays a role in it," said County Manager Joaquin Avino, who ran Dade's Building and Zoning Department in the early 1980s. "Look back in the '60s, '50s, and 40s. Materials tended to be heavier."Adds Flesner: "I think it's just the cost pressure that builders find themselves under. I think you see it more with the large tract builder. If they can save $100 to $200 a house, that's big dollars when you're putting up a lot of houses."To save money, builders pushed for the acceptance of cheaper materials, like staples, thinner plywood and particle board. The 1980s homes that did so poorly in the hurricane were built during a period when the South Florida Building Code was weakened to allow for the inferior materials and techniques."To reduce costs and maximize profits, they were able to get certain building materials approved by using attorneys," said Andrew Allocco, an engineer who inspects homes for prospective buyers.The Herald found that Dade's builders had a considerable influence in the department that inspected them. At the height of the building boom, the building industry contributed one of every three dollars to Metro commission campaigns."Lo and behold, the argument that these contractors and developers used will work in the long run against them," Allocco said. "They had to prove to the board (of Rules and Appeals) that products would withstand a hurricane. Lo and behold, they didn't."The board was warned twice -- in 1983 and again by roofers in 1984 -- that staples weren't working, but did nothing to change the code.INSPECTIONSSystem broke down as new construction proliferatedAt the same time that the building materials were becoming cheaper and construction was increasing, the county's building inspection system was failing to enforce the South Florida Building Code. Through overwork, oversight or outright corruption, county building inspectors allowed the flaws to proliferate.The number of inspectors did not keep up with the pace of construction. Inspectors were pressured to perform up to four times the number of inspections that could properly be done in a day. A computer analysis of building inspections revealed 194 times since 1987 in which inspectors were sent out on more than 50 inspections in one day, more than double the 20 inspection- limit recommended by a grand jury."It's one of the toughest codes, but so what if you don't enforce it or if people don't build to it," said lawyer Miller.State Farm's Flesner concurs: "There are things in the code that need to be fixed. But the bigger concern is enforcement."Grand juries exposed inspectors who didn't get up on roofs and took time off work to go to a bowling alley. A 1986 police investigation found widespread bribery of inspectors."I had a concern about whether or not they were doing a totally honest job in the field," said Ray Goode, who was Dade's county manager in the 1970s."Always in the back of your mind you worry because you have this small army of people out in the field every day checking houses. Do you know or not know if someone is giving them an envelope? Or passing along a case of Coors?"Sergio Pereira, Metro's manager from 1986 until 1988, said it was impossible for inspectors to spot every construction problem."That's very hard to police," Pereira said. "I don't think you can blame government for it. When you had the kind of building boom you had, what are you going to do? Leave an inspector at the building site forever?"After Andrew, Metro-Dade officials swiftly took action in what was in effect a telling admission of the deep flaws in the system.In short order, the county banned staples and particle board and required building inspectors to start checking whether gable-ended roofs are properly braced.Nonetheless, the county can only do so much."I do believe inspection is the second line of defense in this industry," said Ronald Zollo, an engineering professor at the University of Miami. "You may blame it all you want, but it's supposed to be built right in the first place."Herald Staff Writers Luis Feldstein Soto and Don Finefrock contributed to this report.Copyright 1992 Miami Herald |
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| 撮影者 | danxoneil , USA |
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