Effect of Tornado Wind Speeds on Typical Traffic Signs

摘要

Little is known about real-time tornado wind speeds and their effects on infrastructure. The objective of this project is to better understand these relationships through the use of wind tunnel testing. It is valuable to know the behavior of well understood structural systems in different wind conditions and under what circumstances these systems fail. With the wind speed data collected by these 'windicators,' larger structural systems can be designed in a more efficient and safer manner. This data can also be used to increase tornado severity prediction capabilities. A scaled model of a typical Canadian traffic sign (stop sign) was designed at a 1:6 scale to mimic the relationship between bending strength and wind speed, factoring in gusts. Testing was performed with a range of scaled bending capacities and wind speeds. To analyze the data collected, the static and dynamic properties of the scaled sign model need to be investigated and understood. A relationship between rotation angle and static forces showed that a moment of 0.49 Newton meters in model-scale was needed to initiate movement. If this movement reached a critical angle of 15 degrees the model would overturn. Preliminary observations show that at the onset of motion the wind speed was estimated at 12 meters per second. For full scale applications, the 3-second gust velocity to blow a typical stop sign over is required to be at least 180-200 km/h.