Tirey & Associates, P.C.

Consulting Structural Engineers

Project: Concord School

Passive Snow Monitoring System

Location: Concord, Vermont

Completion Date: 2005

 

When the results of a snow load capacity analysis for a school gymnasium showed that there was a significant deficiency in capacity relative to current building code requirements, the owner had few choices to select from if they wanted to continue to use the building throughout the winter. Given the location of the school in northern Vermont, building use through the winter is essential.

 

The option of structurally upgrading the metal building’s snow load capacity would be expensive and intrusive. In order to increase the capacity of both primary and secondary framing elements, it is most practical to reduce spans and tributary load widths to the various elements. This would require the introduction of similar new steel frames and foundations between the existing frames. This solution option was not feasible for the owner due to cost and timing.

 

The alternative solution is low cost but places a monitoring requirement on the owner to insure that the snow on the roof does not exceed the capacity of the structure. A passive snow monitoring system permits visual observation of the snow depth in relation to depth guides. The system includes a measurement device which is a series of 8 rods of increasing height and two different colors assembled in a row on a base. A written plan for observation of snow depth, possible required load measurement action based on the number and color of rods exposed to view, and snow removal actions from the roof provides a matrix for decision making for the owner to ensure that the building occupants are safe.The advantage to this system is that the owner incurs the cost of snow removal from the roof only when it is determined to be necessary, based on actual load measurements.