Posted on 7/5/2012 6:53 AM by Josh Brown
Batten down the hatches. Over the past few years, hurricanes have made headlines and caused billions of dollars in damage to structures and products along the Gulf Coast and eastern seaboard. All the country’s coastlines and low-lying inland areas are susceptible to high wind events associated with these storms and the potential devastation they cause.
If you think the country has seen more active seasons for weather disasters recently, it certainly has. These storms are a phenomenon, and are becoming more and more prevalent along our country’s coastlines. According to a Reuters article in July 2011 the record was nine separate incidences set in 2008. By the end of 2011, weather disasters tallied a record setting 14 billion dollars in damages. This year is off to a roaring start, with double the number of tornados reported as of the first of March.
The most active high wind zones are along the coasts of the Gulf of Mexico and the eastern seaboard. Peak wind speeds can range from 90 mph to in excess of 150 mph. Even if an area has been spared from dealing with these disasters in the past, building owners from the smallest home to sprawling plant, distribution and warehouse facilities have to be prepared for whatever nature blows their way.
Of particular concern are commercial operations, especially warehouses that find themselves increasingly exposed to danger as a result of their masses of overhead dock doors. The potential for billions of dollars in damage to facility and inventory assets when a hurricane makes landfall is motivation enough for building managers to storm proof their operations.
Having a loading dock door that can withstand high winds is crucial to a building’s survival. About 50% of the damage to a distribution center’s contents is a result of the dock doors being ripped from their tracks and off the walls. The risk is significant considering most doorways are an 80 square foot opening and the average distribution center can have dozens, and even hundreds of doors.
Moreover, the door is the only moving part on the building’s structure as most other components – walls, the roof, etc. – are securely fastened into the building materials. In the parts of the country that will experience these devastating storms, commercial buildings must have doors that stand up to the pounding wind and debris, yet do what they are supposed to routinely do, which is open and close to efficiently to handle truck traffic on the loading dock.
If commercial building owners or management aren’t tuned in to the need to avert the damage to their facilities and disruption to their schedules, the insurance companies and consequently, the code writers for state and local governments will remind them. According to Munich Reinsurance America, one of the top providers of property and casualty reinsurance in the U.S., the number of natural disasters has tripled in the last 20 years and 2010 was a record breaker with about 250. CNA in their report “Risk Control in the Warehouse/Distribution Industry”, estimates that 58% of insurance claims dollars are from wind and water damage.
Prior to landfall and 170 mph peak winds from Hurricane Andrew that hit Florida’s Miami-Dade county in 1992, the philosophy was to rebuild damaged buildings. In the wake of Andrew’s devastating $25 billion in damages, Florida taxpayers and the insurance industry grew tired of buildings being rebuilt just to be knocked down again. The a result of Andrew’s impact has lead Florida to enact the country’s toughest state building codes to ensure buildings are tougher than the storms. These extensive regulations encompass 24 product categories and 3,000 pages, with overhead sectional doors being among those products.
Florida is requiring that buildings and their components, including doors, withstand wind pressures generated by winds ranging from 110 mph to 150 mph. In addition, the doors must also stand up to a level of UV rays from the sun that could compromise the strength of the door panels. And it is no wonder Miami-Dade County is leading the building standards charge against Mother Nature in light of the damage Hurricane Andrew left behind.
The Miami-Dade County Building and Neighborhood Compliance (BNC) Department set out to ensure the strictest standards for manufacturers to comply, including those for overhead sectional doors used at many warehouse and distribution facilities. These standards require a notice of acceptance and completion of an Air Pressure Test, Large Missile Impact Test, Cyclic Wind Pressure Loading Test, and a Forced Entry Test among others.
Within the world of building codes, “wind load” refers to the pressures exerted on a structure and the components comprising the structure due to wind. Wind pressures are assumed to act both toward (positive pressure) and away (negative pressure) from a building’s surface.
Wind load rated impactable loading dock doors are stepping into this role as building protectors, already designed to stand up to forces on the inside of the building. But now, these doors are rated to even meet the Miami-Dade requirements for resistance to forces and impacts outside the building.
Under normal conditions plant, warehouse and distribution center loading docks are extremely busy places, with forklifts darting across the dock floor at high speeds within a confined space. Before the advent of impactable sectional doors, the style of overhead doors used in these facilities were similar to a standard garage door, hardly built to take a hit from a forklift much less withstand hurricane force winds.
The widely accepted use of impactable dock doors has enabled distribution centers, manufacturing plants and other commercial facilities to address the common damage and downtime issues that come with forklift impacts, saving considerable damage, energy loss and reducing operating costs to the facility.
The features that allow the these doors to stand up to forklift impacts without suffering damage to the panels or track, include heavy-duty retractable plungers that allow the door to open upon impact as well as an impactable track and strong bottom panel to allow doors to break away easily preventing damage.
If a forklift collides into an impactable dock door, the guide mechanism releases the panel from the door guide, while resetting the door is quick and easy. Just pull the door panels back into the guide tracks and the operation is back in business without damage or downtime.
With a damage resistant door protecting again forklift impacts, it’s no surprise that an easy next step was to include design enhancements to enable their damage resistant doors to stand up to the punch of the high wind events and flying debris from hurricanes, tropical storms or tornados.
The damage resistant polycarbonate skin guards against damage from flying materials as well as provides a layer of UV protect from the sun’s harmful rays that can weaken panels. Its full-height reinforced impactable track and heavy-duty retractable plungers allow the door flexible properties while still maintaining its ridged strength. And finally, as a last layer of extra protection are the slide locks with lock out pins which keep the doors securely in the track that is fixed to the wall during high wind events.
As a way to combat these high wind events in accordance with state of Florida codes, rigorous testing establishes if a door design meets static air pressure resistance required by ANSI/DASMA 108 or ASTM E330 specifications. Though static air pressure (positive and negative) is one issue (measured in lbs/sq ft), some localities are requiring door testing to determine the ability to resist penetration of airborne debris. The testing involves hundreds of simulated wind gusts and impacts from a 2-by-4 stud that is shot from a cannon at 50 feet per second.
Essentially, the impactable door design meets the Florida codes as determined by the testing. The same door panels, which stand up to the forceful impact of speeding forklifts carrying heavy loads, were able to pass the wind gust and projectile tests and
still provide coverage for the doorway. To provide additional assurance to overcome these forces, inside the panels there is a flexible tubular frame reinforced with a steel angle.
The high-density guide tracks mounted flush to the jambs are another part of standard impactable doors, which enable the door to remain attached to the wall. Unlike a standard door “J-Track”, the high-density tracks fight off the most abusive forklift impacts on the inside while providing the necessary strength to withstand wind to the panels when the slide locks are engaged during a storm.
Negative pressures here are the issue. To combat these forces, wind load rated models have multiple slide locks that are mounted securely to a steel plate on the panels. As a storm approaches, the crew can engage the slide locks into holes along the height of the guide track, providing the protection necessary during a high wind load event.
To prepare the door for a high wind event or hurricane landfall, the door is closed and the slide locks are engaged into the guide track and locked out with a pin that is attached to the tracks. Mounting the locking mechanism to the door panels enables dockworkers to quickly and efficiently prepare the door for the high wind event, and then quickly disengage the locks once the storm has passed. Pin placement is an extremely important consideration in facilities that have a large number of these doors with limited time and resources to prepare for a high wind event.
While the Gulf region and other areas along the Atlantic coast, facilities have suffered billions of dollars of damage due to high wind events. Thankfully, today’s optimally designed and stringently tested wind load rated doors can help distribution and warehouses facilities of all sizes obtain reduced property damage and maintain a more secure loading dock after the storm, leading to minimal disruption to the supply chain.
Josh Brown is Door Application Consultant,TKO Doors