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Sensitivity Matrix

II(b) Wind - Additional Detail

Asset Categories   Wind - Additional Detail
Mode Sub-Mode Important Impact-Asset Relationships Threshold Mobile-Specific Detail
Bridges Bridge (Superstructure) Cable-supported bridges and long-span beam structures are often light and flexible, meaning that wind actions may more significantly contribute to overall load for these bridge types. [14] The sensitivity of a particular bridge to wind depends on design considerations such as overall stiffness, mass, and the shape of the deck structure and support conditions. [14] See AASHTO standards and ASCE 7-05 guidelines for specific information on design standards for wind loading and bridges. Many bridge reliability analyses use a target safety margin of around 3.5, meaning that the resistance of any bridge component should be 3.5 times larger than the maximum load effect that could occur during the component's service life. If the bridge begins experiencing heavier traffic loads, increased wind loading, or other types of loading beyond the maximum load design, the margin of safety will decrease. [28] The Cochrane-Africatown bridge is a large cable-stayed bridge. Damage from the collision included damage to the cable stays, external cracked concrete on the superstructure, damage to the concrete barrier system, and a displaced main bridge span. Repair costs were $1.7 million dollars. [36]
Bridge (Substructure)      
Operator Houses (movable bridges) and electrical parts      
Roads and Highways Paved road surface      
Road substructure (gravel base, substructure)    
Unpaved roads      
Stormwater drainage (culverts, side drains, etc)      
Highway, road and street signs and traffic lights   During Hurricanes Katrina and Wilma, a large portion of street signs failed at wind speeds of around 90 mph in Miami-Dade County, a county which has similar design standards to Alabama. [40] The recovery process after Hurricanes Katrina and Wilma included resetting and repairing traffic signals, traffic signs, and streetlights. [40]
Highway and road traffic and service   Highway operations experience the follow impacts during conditions with hurricane force winds of above 74 mph: safety risks, loss of life, loss of visibility, loss of traction, loss of communications and power, road damage. Milder impacts may also be experienced at winds under 74 mph. [40]  
Railroads Electrical Equipment (gates/flashers and signal bungalows) Damaged electrical lines from downed trees, for example, can impacts services.    
Railroad Tracks, Ties, and Ballast      
Railroad services (i.e., operations) Damaged electrical lines from downed trees, for example, can impacts services. Safety risks from hazardous material spills.    
Airports/ Heliports Runway and navigational aids Aircraft have crosswind limits above which they cannot land or take-off. High winds alongside other climate conditions such as rain, hail, lightning, snow, freezing rain, can create conditions where operations may be impeded or delayed, or where planes cannot land/take off, particularly in extreme events such as hurricanes. [64, 12, 6]    
Aircraft Lightning and hail can damage and remove aircraft from operations.
Hail can severely damage aircraft. [39, 49]
  Removing aircraft from operation results in lost revenues and excess maintenance costs. [39]
Airfield buildings and structures (e.g., terminal buildings, hangers, air traffic control tower) Wind damage to structures increases non-linearly as wind speed increases. For example, Powell et al. (2007) found that light, moderate, and severe wind damage thresholds correspond to loss levels of around 2%, 12%, and 60% of insured value. Furthermore, winds greater than or equal to 55 m/s produced about 30 times more loss than winds from 25 to 41 m/s. [76] Aviation control towers, air traffic control centers, emergency aircraft hangers are considered Occupancy Category IV or "essential facilities" by ASCE 7-05. They are given a higher importance factor and must be designed to withstand a greater pressures from wind. [67]  
Services and airport/ heliport operations (e.g., flight departures and arrivals, baggage/cargo transfers, ground transportation) Thunderstorms and other convective weather can close airports, cause delays, and hinder or stop ground operations.
Low ceiling and poor visibility can "severely reduce the capacity of an airport and lead todelays"
Precipitation can decrease visibility, require greater separation distances, decrease breaking effectiveness
Increase in 1-hour mean wind speed can increase the likelihood of flight delays
Storms, high winds with cross-wind components can cause delays
High winds can cause delays in maintenance activities, aircraft turning and runway changes (e.g., crosswinds affect choice of runway) [12, 16, 49, 64]
Pejovic et al. (2009) did not establish a threshold for high winds (indicated by 1-hour mean wind speed above the mean), but found that incremental increases in wind speed above the mean could increase likelihood of delay. [53]
For Heathrow Airport, increase in 1-hour average wind speed above the mean increased probability of delay by 8%.
Cross wind components can cause delays at Mobile Regional and Downtown Airports. [64]
Natural Oil and Gas Pipelines Pipelines, aboveground During Hurricane Frederic, the two natural gas companies (Mobile Gas Service Corporation and the Mobile Gas District Utilities Board of Citronelle) suffered wind-related losses. Repairs consisted of repairing or replacing broken gas mains or services which were damaged by uprooted trees; or replacing meters or aboveground piping which were damaged by buildings shifting or by fallen trees. The sum of the damage sustained by the two companies is estimated to total about $494,000. [50]    
Pipelines, underground      
Pipelines, offshore      
Aboveground infrastructure (e.g., compressor stations, metering stations, other buildings, structures) Based on first-hand observations of structural damage during Hurricane Rita, Reed et al. (2010) documented damage to pumping stations--particularly canopies that became airborne, likely during high winds. [56] Oil and gas buildings and structures that could cause "substantial economic impact and/or mass disruption of day-to-day civilian life in the event of failure" are classified as Occupational Category III and must be designed to withstand higher pressures from wind. [67]
Emergency facilities, ancillary structures required for operation of emergency equipment, and buildings that store highly toxic substances are considered "essential facilities" and must be designed to withstand higher pressures from wind. [67]
 
Utilities for pipelines - electricity      
Electric Power Systems Electric Power Systems Wind speed and duration of strong wind have a statistically-significant effect on power outages, but effects are mixed based on power outage data from different states in the Gulf Coast Region. [35] Wind speed above 20 m/s was the explanatory variable used by Han et al. (2009) in their analysis (p. 201). Han et al. (2009b) investigated the correlation between the number of overhead components and the affects on power outages, but did not establish thresholds over which impacts were more likely to occur. [34, 35]
Analysis of data of damage from Hurricane Rita in Louisiana shows that fragility--defined as the ratio of outages in a parish divided by the total number of customers in that parish for the date of hurricane landfall--was 10 to 20% in sustained wind speeds that were 30% of the equivalent 2-minute sustained wind speed using ASCE 7-05, and was to 80 to 90% in sustained wind speeds that were 60% of the equivalent 2-mintue sustained wind speed. The authors note that other storm variables may also have an impact on line failures. [56]
For example, the Mobile division of the Alabama Power Company sustained $16.12 million in repair and replacement costs for the distribution system. Mobile County sustained 95% of the damages in the division. Damages to the division included 3,790 poles, 1,367 miles of line, 183 switches, and 1,890 transformers.
Marine Ports, Terminals, and Waterways Electrical Equipment Hurricane-force winds can destroy unsheltered equipment or even sheltered equipment if the shelter is damaged or destroyed. [48]    
Terminal Buildings Hurricane-force winds can damage windows, roofs, and potentially collapse entire structures. [48] Port facilities that could cause "substantial economic impact and/or mass disruption of civilian life in the event of failure" are classified as Occupational Category III and must be designed to withstand higher pressures from wind. [67]
Port emergency facilities, ancillary structures required for operation of emergency equipment, and buildings that store highly toxic substances are considered "essential facilities" and must be designed to withstand higher pressures from wind. [67]
 
Channels Additional debris from high winds (man-made equipment) can hinder travel through common routes. Additionally, build-up of debris in channels can reduce channel depth, also hindering travel. an increase in frequency of heavy precipitation events would increase siltation, requiring more frequent dredging. [48]    
Piers, wharves, and berths      
Port services (i.e., operations) Destroyed facilities can disrupt operations. Evacuations can disrupt operations, as well. Inability to handle vessels disrupts operations. [48, 49]    

*Note dollar amounts are not adjusted for inflation.

Updated: 03/27/2014
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