大跨度复杂屋盖积雪漂移堆积机理、过程模拟与实测研究

Snow-induced roof collapses are increasing around the world partly because of the increasing in extreme weather events such as snowstorms. When designing snow-load-sensitive structures, such as large-span roofs and lightweight steel structures which are widely used over the country, snow load is one of the principal design loads. Furthermore, rationale for the code recommended design snow load is not clear and has not been calibrated using newly developed probability methods or verified with field observed snow depth information. This project is mainly focused on estimating the required design snow load considering the physic process of and uncertainty in snow accumulation such that the designed structures are sufficiently safe and economic. To achieve this objective, the tasks of the project are concentrated on: （1）full-scale and model-scale measurements of snow depth on roofs and analysis of factors that influence it; (2) properties of snow pack and the role of wind in the accumulation of snow on roofs; (3) methods of simulating snowdrift with numerical model and in wind tunnel; (4) estimation of the required design snow load on large-span roofs for codified use. The funding of this project will increase the needed research activity in snow load on large-span roofs to reduce possible economic losses and fatalities caused by snowstorms. The tasks and research results are essential for calibrating the codified snow load implemented in the national building code.

随着全球范围内极端天气现象的逐渐增加，因积雪造成的屋盖结构坍塌事故也 在逐渐增多。大跨度和轻型结构是对雪荷载敏感的结构体系，因此雪荷载的取值是其设计过程中的一个重要考虑因素。此外，近年来，大跨度和轻型结构在我国得到大范围应用，对雪荷载设计方法有着十分迫切的应用需求。本项目针对积雪漂移的形成机理、数值模拟方法和风洞试验方法等开展基础研究，并结合实际结构的现场实测结果，对大跨度复杂屋盖的雪荷载分布情况进行系统分析与总结，建立相对完整的雪荷载设计方法。主要研究内容包括：（1）大跨度屋盖积雪分布的现场实测与影响因素分析；（2）积雪的物理性质和风对积雪漂移的作用机理；（3）积雪漂移的数值模拟与风洞试验方法；（4）大跨度复杂屋盖的雪荷载设计方法体系的建立。本项目的开展，可提高我国对屋面雪荷载的认识与研究水平，并可为实际工程的雪荷载取值与我国荷载规范的修订提供依据。

本项目针对积雪漂移的形成机理、数值模拟和风洞试验等开展了一些列研究。主要的研究成果包括：在哈尔滨市内选取若干实际建筑，对其屋盖上的积雪深度进行实地测量，得到整个屋面的积雪分布情况；制作若干屋盖模型置于室外，对其上的积雪和气象条件进行测量。通过这两方面的工作，建立了我国屋面雪荷载的案例数据库。积雪漂移数值模拟与风洞试验研究方面，基于混合流理论，对积雪漂移进行数值建模与计算方法的探索，改进了风雪二相流数值模拟方法；同时探索了利用风洞对积雪漂移进行模拟的试验技术，进行了风雪联合试验相似数的研究。基于以上方法，对雪颗粒的动力粘性及运动特征；雪颗粒的三种运动模式（蠕移、跃移和悬移）在总输运量中的比重；建筑采暖和日照、大气温度对屋面积雪的融化、再冻结的联合作用进行了分析研究，明确了各参数的影响大小。最后，本项目开展了对若干典型屋盖（如平屋面、高低屋面、坡屋面、拱形屋面、球形屋面等）积雪分布情况的试验研究，并开展了大量的参数分析，在此基础上，结合之前所积累的屋面实测结果，改进了屋盖雪荷载的设计方法，为荷载规范的修订和完善、实际工程的设计提供了参考和依据。