Design wind loads for houses in tornadoes

在加拿大和世界各地，严重风暴造成的经济和保险损失持续增长。加拿大容易受到严重风暴的影响，典型的例子是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）和2003年的胡安飓风（8人死亡）。木结构房屋是我们最常见的结构类型，由于大多数房屋没有经过工程设计，抗风功能有限，因此很容易受到影响。主要的安全问题是保持整个房子在基础上，屋顶与墙壁相连。一旦做到这一点，生命损失和经济损失就会降到最低。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，风对房屋的影响现在已经有了一定的了解。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，龙卷风对房屋的风荷载在很大程度上是未知的。尽管由于损失不断增加，减少龙卷风损失的设计才刚刚开始被讨论，但很少有设施可以产生足够大的龙卷风漩涡，从而可以对建筑物进行测试，这也是一个障碍。随着WindEEE Dome的发展，这种情况最近发生了变化。该提案的目的是利用该设施作为确定龙卷风中木结构房屋设计风荷载的基础。特别是，(i)房屋形状，（ii）周围地形，（iii）邻里模式，以及（iv）静压降和内部压力对风荷载的影响将在龙卷风状漩涡存在的情况下进行检查。设计风荷载将基于对这些参数中的每个参数使用一系列因素，相对于目前在建筑规范中使用的因素。这种方法将简化实践工程师的设计，并允许随着其他因素的进一步了解而修改代码。在本次调查过程中，至少有五名学生将接受培训。

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.