Characterization of joint wind–snow hazard for performance-based design

Load combinations involving wind and snow load (effects) govern in the design of some types of structures located in heavy snow regions, such as long-span bridges or roof systems in cases where snow drifts could become significant. While load standards such as ASCE 7 provide guidance on combining design loads for design for life safety, guidance is not yet available for other performance levels (limit states). This is expected to become more significant as performance based-design procedures continue to evolve and gain acceptance in the design community. This paper presents an approach to statistically characterize the joint wind–snow hazard for use in performance-based design. Wind loads and snow loads are modeled as renewal pulse processes and combined within a numerical simulation. The results are then used to construct the joint wind–snow hazard level contours corresponding to different annual exceedance probabilities. The procedure described herein, along with the results for the specific cases considered, provide a useful context for relating design loads associated with specific hazard levels to those established for use in life safety design, such as those found in ASCE 7. This enables a discussion on the relationship between strength-based and hazard-specific design values, and between limit state design and performance-based design load combinations.

▸ An approach is presented to characterizing the joint wind–snow hazard. ▸ Wind and snow loads are modeled using renewal pulse processes. ▸ Hazard contours are developed from the joint density obtained from simulation results. ▸ Two different snow climates are considered. ▸ A partial factor approach is proposed, similar to what is used in ASCE 7.