Hurricane Hugo, Puerto Rico, the Virgin Islands, and Charleston, South Carolina, September 17-22, 1989 (1994) / Chapter Skim
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Surface Wind Speeds and Property Damage
Surface Wind Speeds and Property Damage
Pages 82-114
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From page 82... ...
INTRODUCTION To assess properly the performance of buildings and other structures subjected to extreme natural events such as Hurricane Hugo and to establish the severity of the event itself, it is essential to have accurate wind-speed information. It is not unusual to encounter reports of extraordinarily high wind speeds following a destructive hurricane, and Hugo was no exception.
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From page 83... ...
To be consistent with standard wind-speed measurement and reporting procedures, the speeds described in the following sections refer either to peak gusts or sustained speeds at a height of 10 m in flat, open terrain, typical of airport exposures. It is important to note that wind speeds measured under nonstandard conditions may differ widely from standard measurements.
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From page 84... ...
Cro~x by three members of the CND investigative team 5 days after the storm indicated that the most severe damage was located along the north coast from the mouth of the Salt River eastward to the end of the island. This observation is consistent with the San Juan radar images, which show very intense convective bands developing to the northeast of Christiansted and moving over the area directly off the ocean from about 0530 to 0630 GMT.
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From page 85... ...
During this time interval, the wind directions shifted gradually from northeast to southeast. Based on observations of damage made from the air, it was clear that the wind speeds over St.
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From page 86... ...
Culebra Strong winds from the northeast began to affect Culebra at about 0900 GMT when Hugo was located approximately 75 km to the south-southeast. Data from San Juan radar indicate that intense rainbands began to move over Culebra from the northeast at 1020 GMT.
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From page 87... ...
Because the winds there would have been directly off the ocean, speeds slightly higher than those at Roosevelt Roads Naval Station may have been reached. DESIGN WIND SPEEDS While the specified design wind speeds for the affected areas can provide some insight into the wind resistance of local structures, they are perhaps more an indicator of perceived importance of wind loading as a design consideration.
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From page 88... ...
0 400 800 1200 1600 GMr FIGURE ~2 Gust speeds measured at San Juan International Airport. Humcane Hugo 6G - 27G ~ ED 185 0 90 ~ lo 4360_ 4; 270 _ 1 3Q _ 90 C _ o lo 20Q~
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From page 89... ...
There are no provisions in the building code for local terrain effects or for classification of buildings as to occupancy or function. If typical surface-pressure coefficients of 0.S and -0.5 are assumed for windward and leeward sides, respectively, the required design pressures can be converted to corresponding reference wind speeds (assumed to be sustained speed over a 10 minute period in open territory)
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From page 90... ...
These wind speeds, referenced to standard exposure conditions, TABLE ~2 Code-Specified Design Wind Speeds for the Caribbean Region. Source of Requirement Sustained Speed (knots)
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From page 91... ...
Based on the code-specified design speeds listed in Table 4-2 and the probable maximum wind speeds listed in Table 4-3, the following observations can be made: The basic design speed implied by the Virgin Islands Building Code was exceeded on St.
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From page 92... ...
There are several new housing developments in the Christiansted area, and one of these, located on the north slope directly east of Christiansted, is shown in Figure 4-4. It is believed that local terrain characteristics caused a significant increase in wind speed, perhaps as much as 20 percent, in this area.
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From page 93... ...
Surface Hand Speeds and Property Damage I_ FIGURE ~3 Condominium at Coakley Bay, St. Craig FIGURE 4-4 Housing development east of Christiansted, St.
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From page 94... ...
Again, the terrain undoubtedly caused an increase in wind speed, and the strongest winds were approximately face-on to the failed wall. It appears that the roof sheets and purlins were carried away as a unit, leaving the end frame unsupported and allowing the windward wall to collapse.
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From page 95... ...
_ . rem I ~ FIGURE ~7 Metal building west of Christiansted, St.
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From page 96... ...
The most damaging winds were from the northeast, and one report put the wind speeds at I86 knots (214 mph) for this location.
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From page 97... ...
Groin ._ FIGURE ~10 Damaged oil storage tanks, St. Croix.
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From page 98... ...
Cro~c Humcane Hugo A_ ~1 _= ,_ I_ I_ Damage to the metal building in the foreground indicates wind directions from the northeast around to the south, and this is consistent with the movement of Hugo. A portion of another metal building is shown in Figure 4-12.
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From page 99... ...
Surface grad Speeds and Property Damage e—V~ , __ D ~1 ' ~ -. L_ __ , ..J FIGURE ~12 Metal building at Alexander Hamilton Airport, St.
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From page 100... ...
San Juan radar showed intense rainbands moving over the island from the northeast and thus the possibility of locally intense winds due to m~crobursts (vertical momentum transport) cannot be ruled out.
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From page 101... ...
Surface Band Speeds and Property Damage FIGURE ~15 Resort hotel, St. Thomas .
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From page 102... ...
This was not the case in Puerto Rico. Therefore, though the observed damage suggests a likely m~croburst near Charlotte Amalie and elsewhere, the occurrence of m~crobursts in Puerto Rico is only a matter of informed speculation.
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From page 103... ...
Surface Wed Speeds and Property Damage _~ _~ _— lo_ FIGURE ~18 Houses on post-and-beam supports, Vieques. __ Hi_ Cad ~,L.-YD - 1 =;E .Y, Ei Hi_ FIGURE ~19 Housing development, Vieques.
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From page 104... ...
The quality of construction was poor, and it is doubtful that there was any attempt to comply with the Puerto Rico Building Regulation. In addition, the terrain slopes steeply upward to the west, which is very likely to have caused an acceleration of the intense easterly winds from Hugo.
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From page 105... ...
Surface Hand Speeds and Propel Damage MEL FIGURE ~21 Housing development next to airport, Culebra. FIGURE ~22 Small craft in Ensenada Honda, Culebra.
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From page 106... ...
Neither location experienced a clear lull from eye passage as did Cape San Juan at the extreme northeast tip of the island, although Roosevelt Roads came close. Figure 4-24 shows two reinforced concrete buildings on the east coast of Puerto Rico between Cape San Juan and Fajardo.
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From page 107... ...
Surface Wind Speeds and Property Damage __—e ~ .
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From page 108... ...
108 Humcane Hugo FIGURE ~26 Horizontal construction joint in shearwall, Dos Marinas.
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From page 109... ...
The roof slab is 100 to 125 mm thick. As with the highrise reinforced concrete buildings just described, the seismic requirements of the building code governed the design, and the substantial dead loads made this type of structure highly resistant to Hugo's wind forces.
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From page 110... ...
FIGURE ~29 Reinforced concrete house, Fajardo, Puerto Rico. Humcane Hugo
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From page 111... ...
Thomas approximately 40 years. The basic wind speed implied by the Virgin Islands Building Code corresponds to an MRI of 15 years.
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From page 112... ...
112 at' FIGURE ~31 Damage to curtain wall, San Juan FIGURE ~32 Damage to curtain wall near street level, San Juan. Humcane Hugo l
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From page 113... ...
1990. Hurricane Hugo in the Caribbean Assessment of Surface Wind Speeds.
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From page 114... ...
10:~-22. Virgin Islands Building Code.
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