Building Damage in South Carolina Caused by the Tornadoes of March 28, 1984 (1985) / Chapter Skim
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'PUBLIC BUILDINGS'
'PUBLIC BUILDINGS'
Pages 16-35
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From page 16... ...
One wing of a private school, the Richard Winn Academy, of similar construction also suffered severe damage, mostly from the wind but possibly also from school buses reportedly seen flying through the air during the tornado. The construction of this part of the school followed the normal practice of using unreinforced walls and short roof anchors.
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l7 FIGURE 20 Dance academy in Newberry. FIGURE 2l Auto parts store in Newberry.
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l8 FIGURE 22 Masonry retail store in Winnsboro. FIGURE 23 Richard Winn Academy in Winnsboro.
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l9 FIGURE 24 Classroom at Richard Winn Academy. FIGURE 25 Classroom at Richard Winn Academy.
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20 FIGURE 26 Church in Winnsboro. FIGURE 27 Detail of church showing roof-wall connection.
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The metal deck was spot welded to bar joists (metal truss rafters) that spanned between girders or between girders and masonry walls.
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22 FIGURE 28 Fairfield County Community Center in Winnsboro. FIGURE 29 Detail of Fairfield County Community Center.
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23 FIGURE 30 Gymnasium of Richard Winn Academy. FIGURE 3l Steel-framed retail store in Winnsboro.
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1 f T ! .( i 1 12.0 FIGURE 33 Plan of Northwood Village Shopping Center in Bennettsville.
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Next to the department store, the small unoccupied local store lost all its supporting walls, but the center line of columns remained upright (Figure 36)
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FIGURE 36 Surviving framing in local store.
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27 FIGURE 37 Roof collapse in drug store. FIGURE 38 Failure of beam joint.
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28 FIGURE 39 Failure of front wall in supermarket. , FIGURE 40 Failure of roof in supermarket.
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In checking the roof system, several points became evident. The bar joists were quite adequate for the design gravity loads provided the decking supplied lateral restraint to the compression flanges of the bar joists.
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Despite the important role played by the walls, little attention appears to have been paid to their design. They were apparently sized to meet the absolute maximum ratio of unsupported distance to thickness permitted by the Standard Building Code in effect at the time of construction -- l8 -- with the roof being deemed to provide support.
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From page 31... ...
, •y'•fe^v.".", BOIl 1* 1 CHORD OF JOIST EXTENDED TO NEAREST COLUMN FOR BRACING COLUMN CAP PLATE 7.5 INCH x 12.5 INCH x 0.5 INCH STANDARD BOLTED BEAM CONNECTION _ GIRDER M-SECTION 5 INCH DIAMETER "STANDARD STEEL PIPE b im.H DIAMETER PIPE ~ -- -- 11 IK ICH x 7 INCH x 0.75 INCH BASE H 0.75 INCH DIAMETER ANCHOR B PLATE OLT 2 INCH NON SHRINK A GROUT \ y -- MIT , \ / / // ,• 4 IN( H CONCRETE SLAB VARIES fcsssssg ^ 2 •: •».• •.•••'..•»'.•,••" ',•.••: t \if'f'-, OVARIES ^ L 1 >iii i/; 1.0 FT /,» _.'-" •'•>»':;li §|^ 6 K BARS , • 6 15 BARS 5.0 FT (TYPICAL)
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From page 32... ...
Without the restraint and shelter provided by this canopy, the front wall of the department store possessed very little wind resistance. To determine how the failure of certain components influenced the wind loads on the remaining components, a study was conducted in the structural engineering wind tunnel at Clemson University using a l to 288 scale model of the shopping center and a boundary layer appropriate for the local terrain (Wright, l984)
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With these factors of safety, components designed to meet the pressures specified in the Southern Standard Building Code should not have experienced serious damage until the wind speed reached nearly l50 mph. If at that stage the front wall had failed, failure of the roof sheeting would soon follow.
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be made of the strength of the walls. No data were available concerning the ability of the roof sheeting to resist uplift forces or the wind resistance of the wood canopy, it is highly unlikely, however, that they would have met the code design requirements with a factor of safety of more than 2, and the roof sheeting is known to have failed before the walls.
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From page 35... ...
by a loss of restraint to the walls and a consequent reduction in structural capacity far greater than the reduction in load. Since these walls also provide the lateral bracing for the vertical load-bearing system, the conditions for a progressive collapse are established as soon as the roof diaphragm fails, it is particularly disturbing that the diaphragm's integrity, and ultimately that of the whole structure, depends upon such minor details as the window frame to masonry connections, the design of the walkway canopy, and the welding of the metal decking to the bar joists.
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