Wind speed not only affects the truck dumper itself, but also the truck and /or trailer. Understanding how wind speed impacts truck dumpers is critical for proper design and safe operation.
Parallel Wind Direction
Wind acting parallel with the truck dumper, referred to as a ‘head’ or ‘tail’ wind, applies the greatest force directly to the deck. A head wind blowing from the front to the back of the dumper typically does not present significant issues when the dumper is loaded. Even with the deck unloaded, the dumper typically has sufficient mass to counteract wind forces; however, raising the deck while unloaded during high winds is not recommended.
A tail wind blowing from the back to the front of the dumper typically places the most stress on both the structure and hydraulic system.
This added stress occurs because the wind acts in the same direction as the gravity load of the truck or trailer. Depending on wind speed and direction, a tailwind can add several thousand pounds of additional force to the deck. If the deck is aged or the truck is heavier than the dumper’s load rating, the additional load can cause structural damage to the main frame.
Cross Wind
Cross winds are of greater concern than parallel winds, despite putting less force on the dumper itself. The reason for this is the truck and trailer, and not the dumper deck. The trailer presents a large surface like a sail for the wind to act upon. The trailer is most vulnerable to wind while it is in the raised position after the contents have been unloaded. An empty trailer is relatively light compared to its surface area. High wind speeds on an empty trailer can put a twisting force through the trailer and into the dumper frame, regardless of whether the tractor is tied down or not. In a worst-case scenario, the wind will cause the trailer to shift on the deck, creating more torsional forces on the dumper and potentially causing the truck and/or trailer to fall. Safety/retainer hoops are a last-resort feature and are not designed to restrain trailers during high-wind events.
combination winds
Wind very rarely acts completely parallel or perpendicular to specific pieces of equipment. Wind direction can change rapidly, and swirling or turbulent winds can create a combination of forces in multiple directions. Surrounding geographic features, buildings, or nearby equipment can create additional currents or wind turbulence, adding to the complexity of the wind loading.
Design Parameters
Airoflex dumpers are designed for site-specific wind loading based on ASCE hazard data. This allows the wind forces to be accounted for in the major axes of the dumper for both structural design and foundation loads. The design wind speed may be very high, and is NOT the operational wind speed for the dumper.
Operational Parameters
Airoflex recommends a maximum wind speed of 20 miles per hour, based on a 3-second gust, as the cut-off for operating any truck dumper. Larger models (65-foot deck length and up), dumpers located on flat or open terrain, or areas prone to high wind gusts, may require a lower wind speed maximum. Smaller dumpers, or dumpers that are blocked from the wind by buildings or other structures, may be able to operate safely at higher reported wind speeds due to being shielded from the full wind force.
Any increase in the dumper’s maximum operational wind speed is site-specific and depends on the user’s safety procedures. The user assumes full responsibility for operating above the Airoflex-recommended guidelines and should not do so without proper consideration and safety protocols in place. When deciding whether to operate a truck dumper under specific weather or wind conditions, a general rule of thumb is to consider crane operation. If a crane would not be operated at the current wind speed or weather conditions, then a truck dumper should not be operated.
Conclusion
Wind forces have a great effect on the design and operation of truck dumpers. Understanding how they interact with a truck dumper can not only help with better structural designs but also allow for safe and continued operations. Please contact Airoflex with any questions about design or operation regarding wind speed.