Design wind loads for houses in tornadoes

在加拿大和世界各地，由于严重风暴造成的经济和保险损失继续增长。加拿大容易受到严重风暴的影响，重要的例子是1985年的巴里龙卷风(12人死亡，3亿美元)，1987年的埃德蒙顿龙卷风(27人死亡，6.7亿美元)，以及2003年的飓风胡安(8人死亡)。木结构房屋是我们最常见的结构类型，由于大多数房屋都不是经过设计的，防风功能有限，因此很容易受到攻击。主要的安全问题与保持整个房子在地基上，屋顶与墙壁相连有关。当实现这一点时，生命损失和经济损失将被降至最低。**由于多年的风洞研究以及最近对全尺寸结构以及建筑部件和材料的结构测试，在飓风等大规模风暴中对房屋的风力影响现在是合理的。众所周知，加强建筑规范可以减少这些风暴造成的损失。相比之下，在龙卷风中，房屋上的风荷载在很大程度上是未知的。尽管由于龙卷风造成的损失不断增加，减轻龙卷风损失的设计才刚刚开始讨论，但几乎没有设施可以产生足够大的龙卷风般的漩涡，以至于建筑物可以进行测试，这也是一个障碍。最近，随着WindEEE穹顶的开发，这种情况发生了变化。这项建议的目的是利用这一设施作为基础，确定龙卷风中木结构房屋的设计风荷载。特别是，(I)房屋的形状，(Ii)周围地形和(Iii)邻里模式，以及(Iv)静压降和内部压力，将在龙卷风状涡流存在的情况下对风荷载的影响进行研究。设计风荷载将基于对每个参数使用的一系列系数，这些系数相对于建筑规范中当前使用的系数。这种方法将简化实践工程师的设计，并允许随着其他因素变得更好地理解而修改代码。在调查过程中，至少将培训五名学生。*

Economic and insured losses due to severe storms continue to grow, both in Canada and around the world. Canada is vulnerable to severe wind storms, with significant examples being the Barrie tornado in 1985 (12 lives, $300M), the Edmonton tornado in 1987 (27 lives, $670M), and Hurricane Juan in 2003 (8 lives). Wood-frame houses, our most common type of structure, are vulnerable because of the fact that most houses are not engineered and have limited wind-resistant features. The primary safety issue pertains to keeping the whole house on the foundation, and the roof connected to the walls. When this is achieved, loss of life and economic losses are minimized.** Wind effects on houses in large-scale storms, such as hurricanes, are now reasonably known because of many years of wind tunnel studies and, more recently, structural testing of full-scale structures along with building components and materials. It is well established that enhanced building codes can reduce losses in these storms. In contrast, wind loads on houses in tornadoes are largely unknown. Notwithstanding the fact that design to mitigate losses in tornadoes is only just beginning to be discussed due to the ever increasing losses, the fact that there are few facilities which can create tornado-like vortices of large enough size that buildings can be tested has also been a barrier. This has changed recently, with the development of the WindEEE Dome. The objective of this proposal is to use this facility as a basis to determine design wind loads for wood-frame houses in tornadoes. In particular, the effects of the (i) shape of the house, the (ii) surrounding terrain and (iii) neighbourhood patterns, along with the (iv) static-pressure drop and internal pressures, on wind loads will be examined in the presence tornado-like vortices. Design wind loads will be based on using a series of factors for each of these parameters, relative to those currently used in building codes. This approach will simplify design for practicing engineers and allow codes to be modified as other factors become more well understood. At least five students will be trained during the course of this investigation.****