Uniform Snow Loads on Structures

Data on ground and roof snow loads for 199 structures are analyzed. Relationships between ground-to-roof conversion factor for uniform roof loads and parameters such as roof slope, exposure and thermal characteristics are investigated. The conversion factor was found to be most strongly influenced by exposure. On the average, there was about a 35% difference in conversion factors for windswept and sheltered roofs. The conversion factor was influenced to a lesser degree by thermal characteristics. On the average, there was about a 20% difference in conversion factors for heated and unheated structures. Roof slopes between 0° and 35 ° did not have an observable effect upon the conversion factors. An expected value relationship for the conversion factor was established. The variation of observed values about the expected value was modeled by a log-normal error term with a standard deviation for ln(ε) = 0.42. Comparisons with existing codes and standards indicate that their recommended conversion factors are, on average, larger than measured values.