【行业知识】澳大利亚风荷载设计

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GUIDE TO WIND CLASSIFICATION

本文摘录自澳洲屋面瓦材料商的产品手册

Introduction

An accurate wind classification is essential input to determining the installation standard to ensure that the performance of a tiled roof is not compromised by environmental conditions.

准确的风力分类是确定安装标准的关键，以确保瓦片屋顶的性能不受环境条件的影响。

It is normal practice that the advice of a suitably qualified building engineer be sort to accurately determine the Wind Classification for a site.

一个合格的建筑工程师的建议是正确确定一个场地的风的等级，这是正常的做法。

The information provided in this guide has been created to assist the designer or the main contractor in their responsibility in determining the appropriate wind classification (or design wind velocity (m/s)) for a site.

本指南中提供的信息是为了帮助设计师或主承包商确定合适的风的分类(或设计风速(m/s))。

Also note that the process used in the guide is an approximate method for estimating wind classifications for residential structures only. For full analysis refer to Australian/NZ Standards;

还要注意的是，指南中使用的方法只是估算住宅结构风分类的近似方法。全面分析参照澳大利亚/新西兰标准;

• AS/NZS 1170.2:2011 and by its Amendment 2 (2012);Definition of Terrain category

•AS/NZS 1170.2:2011及其修正案2(2012);地形类别的定义

• AS1170.2-2002 – Structural design actions, Part 2:Wind actions; This Standard is generally applicable to determining the wind loads on any structure.

•AS1170.2-2002 -结构设计动作，第2部分:风的动作;本标准一般适用于确定任何结构的风荷载。

• AS 4055-2002: Wind loads for housing”. In NZ, the relevant standard is NZS 4203.

•AS 4055-2002:房屋的风荷载。在新西兰，相关标准是NZS 4203。

It is important to categorize each building on a case-by-case basis. Each site should be assessed individually for its wind classification. Each building must be assessed for compliance with geometry and for evaluation of pressures.

重要的是要根据具体情况对每个建筑物进行分类。每个场地都应该根据其风力分类进行单独评估。每一栋建筑都必须进行几何形状和压力评估。

Therefore, Monier Roofing does not accept liability for any loss or damage suffered as a result of any errors in the interpretation or application of this design guide. Monier Roofing recommends that the advice of a suitably qualified building engineer is sort in assessing the wind classification of a particular site.

因此，蒙乃尔屋面不承担由于本设计指南的解释或应用错误而造成的任何损失或损害的责任。Monier屋面公司建议，一个合格的建筑工程师的建议是在评估特定场地的风的分类。

What is wind classification

什么是风的分类

The wind classification relates to gust wind speeds (m/s) that affecting a given site. The determination of a wind classification is critical in ensuring that a building is designed and constructed to the level appropriate to withstand the wind forces it will be subjected to. The wind classifications defined in the standards are summarised in the Table 1 below:

风的分类涉及影响某一地点的阵风风速(m/s)。确定风的等级对于确保一座建筑的设计和建造达到适当的水平以承受它将要承受的风力是至关重要的。《标准》内所界定的风力分类摘要载于下表1:

TABLE 1 – WIND CLASSICATION CONVERSION TABLE

表1 -风分级换算表

Determining a wind speed classification

确定风速等级

The selection of wind speed classification for a house depends on the conditions at the site of the house. The classification shall be determined from Table 2 on Page 8 using the following site conditions:

风速等级的选择取决于房屋所在地的条件。根据第8页的表2，使用以下场地条件确定分类:

STEP 1 The region where the site is located as defined in Figure 1 (Region A B C or D as given in AS/NZS 1170.2).

第一步，定义所在区域(AS /NZS 1170.2中给出的A、B、C或D区域),如图1。

STEP 2 The terrain that surrounds or is likely to surround the site within the next 5 years, as defined in Figure 2 on Page 4

第二步，如图2所示，未来5年内，场地周围或可能会被包围的地形

STEP 3 The topography of the site, as defined in Figure 3 on Page 5

第三步，场地的地形，如图3所示

STEP 4 The shielding that a structure is subjected to, as defined in Figure 4 on Page 6 FS PS or NS

步骤4结构所受的屏蔽，如FS PS或NS，见图4

Step 1. Geographic wind speed region

Please note: Specific design wind speed recommendations are available for some regions via government recommended websites. Refer to the links below for specific regionally information;

请注意:某些地区的具体设计风速建议可通过政府推荐网站获得。有关具体的区域信息，请参阅下面的链接;

> SOUTH AUSTRALIA http://tinyurl.com/mns36yv

Step 2. Selection of terrain category

Terrain categories are used for determining a structure’s exposure to wind as a result of terrain that surrounds it.

The terrain category for a housing site is a measure of the lowest effective surface roughness from any radial direction within a distance of 500 m of the proposed housing site.

地形类别是用来确定一个结构暴露在风的结果，地形围绕它。
住宅用地的地形类别是在距离拟建住宅用地500米范围内的任何径向的最低有效表面粗糙度的量度。

It shall be based on the likely terrain five years after design.

The terrain category for a housing site shall be identified by the notation TC1, TC1.5, TC2, TC2.5 or TC3 and shall be determined as follows:

它应该基于设计后五年的可能地形。
房屋用地的地形类别应以TC1、TC1.5、TC2、TC2.5或TC3表示，并应确定如下:

Supporting Notes:

Well established trees may be considered as obstructions for evaluation of terrain

category.

建立良好的树木可视为地形类别评估的障碍。

In selecting a terrain category due regard to the permanence of the obstructions should be made.

在选择地形类别时，应充分考虑障碍物的持久性。

Supporting Notes:

In urban situations, roads, rivers, small lakes or canals less than 200 m wide shall be considered to form part of normal ‘Terrain Category 3’ terrain. Parks and other open spaces less than 250 000 m2 in area shall also be considered to form part of normal ‘Terrain Category 3’ terrain provided they are not within 500 m of each other,or not within 500 m of open country.

在城市情况下，200米以下的道路、河流、小湖泊或运河应视为正常的“第3类地形”地形的一部分。面积少于25万平方米的公园及其他休憩用地，如彼此相距不足500米，或相距不足500米，亦应被视为构成一般“第3类地形”的一部分。

Housing sites less than 200 m from the boundaries of open areas larger than 250 000 m2, e.g. golf courses, that are completely surrounded by urban terrain,shall be considered to have the terrain category applicable to the open area itself Shielding provisions may still apply to these sites.

距离大于250000平方米的开放区域边界200米以内的住房场地，如高尔夫球场，完全被城市地形所包围，应考虑将地形类别适用于开放区域本身，屏蔽规定仍可适用于这些场地。

Housing sites less than 500 m from the edge of a development shall be classified as the applicable terrain that adjoins the development, i.e. TC1, TC1.5, TC2, TC2.5 or TC3, as applicable.

距离开发项目边缘不足500米的住宅用地，应划分为与开发项目相邻的适用地形，即TC1、TC1.5、TC2、TC2.5或TC3(视情况而定)。

Where the water body is large (i.e. the wind has been blowing over the water for more than 10 km), then wind has the chance to develop long wavelength waves that will shoal on reaching the shore irrespective of the wind. Hence:

当水体较大时(即风已吹过水面超过10公里)，风就有机会形成长波，不管风如何吹，这些长波到达岸边时都会形成浅滩。因此:

(a) Water bodies less than 200 m wide in the direction that the wind is blowing to affect a site do not affect the terrain category.在受风影响地点的方向上，不足200米宽的水体不影响地形类别。

(b) Water bodies greater than 200 m wide, but less than 10 km wide in the direction that the wind is blowing to affect a site are deemed to be Terrain Category 1.在风向影响某一地点的方向上，宽逾200米但宽不足10公里的水体被视为第一类地形。

(c) Only water bodies greater than 10 km wide in the direction that the wind is blowing to affect a site are deemed to be Terrain Category 1.5.只有在受风影响的地点的方向上超过10公里宽的水体才被视为1.5类地形。

Terrain Category 2.5 addresses acreage subdivisions where the house density is less than 10 per hectare. Where trees are large and robust (similar size to houses) then wooded areas with:

地形类别2.5针对的是房屋密度低于每公顷10公顷的细分区域。树木粗壮(与房屋大小相似)，然后有以下树木的林地:

(i) Fewer than 2 large trees per hectare can be categorized as TC2.每公顷少于2棵大树可列为2级树木。

(ii) Between 2 and 10 large trees per hectare can be categorized as TC2.5.每公顷2到10棵大树可以被归类为TC2.5。

(iii) More than 10 large trees per hectare can be categorized as TC3.每公顷超过10棵大树可列为TC3。

In some cases, the 500 m radius circle may contain combinations of smooth features. For example, a small lake with diameter less than 200 m may be adjoined by a park also with width less than 200 m. However, the combine width of smooth features is greater than 200 m and the lake should be considered as part of the park, giving limiting terrain category for the building at the centre of the 500 m radius circle as Terrain Category 2.

在某些情况下，500米半径的圆可能包含平滑特征的组合。例如，直径小于200米的小湖可以与宽度小于200米的公园相邻。然而，平滑特征的结合宽度大于200米，湖泊应该被视为公园的一部分，将半径为500米的建筑的限制地形类别作为地形类别2。

Step 3. Selection of topography

The topographic classification determines the effect of wind on a structure due to its location on a hill, ridge or escarpment relative to the height and slope of a hill, ridge or escarpment.

地形分类决定了风对结构的影响，这是由于风的位置相对于山、脊或陡坡的高度和坡度而决定的。

A hill, ridge or escarpment is a natural feature that rises in height by more than 3° from the surrounding area. The slope of a hill, ridge or escarpment is measured by measuring the slope throughout the top half of the hill, ridge or escarpment at its steepest point. The second consideration is to determine whether the structure is located in the bottom, middle or top third of the hill, ridge or escarpment in terms of height.

山丘、山脊或陡坡是一种自然地貌，其高度比周围地区高出3度以上。山坡、山脊或陡坡的坡度是通过测量整个山坡、山脊或陡坡最陡点的上半部分的坡度来测量的。第二个需要考虑的是，根据高度，确定建筑物是位于山脚、山脊或陡坡的底部、中部或顶部三分之一处。

With the slope and the position of the structure known, the adjacent diagrams may be used to determine the topographic classification i.e T0, T1,T2, and T3.

根据已知的坡度和结构的位置，可以用相邻的图来确定地形分类T0 ,T1 ,T2 ,T3。

In assessing the wind pressures on any structure, the prevailing wind direction must be assessed and if unknown, wind pressures from all wind directions should be assessed.

在评估任何建筑物的风压时，必须评估盛行风向，如风向未知，则须评估所有风向的风压。

In areas where the maximum slope does not exceed 1 in 20 (approximately 3°) the topographic classification shall be T0.

在最大坡度不超过1 / 20(约3°)的地区，地形分类为T0。

Step 4. Selection of shielding

Shielding classification is required as wind speeds on a house is influenced by obstructions around the house that are of similar size. Shielding classification should be considered based on the likely shielding five years hence.

由于风速受房屋周围大小相似的障碍物影响，故需要对房屋进行防护分类。屏蔽等级应该根据五年以后可能出现的屏蔽来考虑。

In Geographic Wind Speed Regions A and B trees or groups of trees with similar face area to houses may be considered as shielding elements. In Geographic Wind Speed Regions C and D trees and vegetation shall not be considered as shielding elements.

在地理风速区，A和B树或与房屋表面面积相似的树群可视为屏蔽元素。在地理风速区C和D，树木和植被不能作为屏蔽元素。

This is because the long duration of the wind events in tropical cyclones can denude the trees and reduce their effectiveness as obstructions.

这是因为在热带气旋中，长时间的风力事件会破坏树木，降低其作为障碍物的有效性。

The shielding class for a housing site shall be identified by the notation FS, PS or NS, and shall be determined as follows:

住宅场地的屏蔽等级应由FS、PS或NS标识，并应确定如下:

(a) Full shielding FS

The application of full shielding shall be appropriate for typical suburban development greater than or equal to 10 houses, or similar size obstructions per hectare.

全屏蔽应适用于典型的郊区发展大于或等于10间房屋，或类似大小的障碍物每公顷。

Full shielding shall apply where at least two rows of houses or similar size permanent obstructions surround the house on all sides. In Regions A and B, permanent heavily wooded areas within 100 m of site provide full shielding.

在房屋周围至少有两排房屋或类似大小的永久性障碍物时，应采用全屏蔽。在A和B区域，100米范围内的永久性重林地提供了完全的保护。

The effects of roads or other open areas with a distance measured in any direction of less than 100 m shall be ignored. However, the first two rows of houses abutting permanent open areas with a least dimension greater than 100 m, such as parklands, large expanses of water and airfields, shall be considered to have either partial shielding or no shielding.

在任何方向测量的距离小于100米的道路或其他开放地区的影响应予以忽略。但是，与面积至少大于100米的永久性空地相邻的前两排房屋，如公园地、大片水域和机场，应视为部分屏蔽或无屏蔽。

(b) Partial shielding PS

Partial shielding shall apply to intermediate situations where there are at least 2.5 houses or sheds per hectare, such as acreage type suburban development or wooded parkland.

部分屏蔽应适用于每公顷至少有2.5间房屋或棚屋的中间情况，如种植面积式郊区开发或林地。

The second row of houses abutting open parkland, open water or airfields may be classified as having partial shielding.

与开放的公园、开放的水域或机场毗连的第二排房屋可被归类为部分屏蔽。

(c) No shielding NS

No shielding shall apply where there are no permanent obstructions or where there are less than 2.5 obstructions per hectare, such as the row of houses or single houses abutting open parklands, open water or airfields.

在没有永久性障碍物或每公顷面积小于2.5个障碍物的地方，如与开阔的公园、开阔的水域或机场毗连的一排房屋或单幢房屋，不得使用屏蔽。

Recent amendments of AS/NZS 1170.2 provide that where buildings are situated on steeply rising land, the roof of a building being designed will not be shielded by the roof of a similar-sized building lower on the slope. Higher topographic classes are associated with steeper slopes, for which full shielding is not appropriate.

最近修订的AS/NZS 1170.2规定，当建筑物位于陡峭上升的土地上时，正在设计的建筑物的屋顶将不会受到位于斜坡较低位置的类似大小建筑物的屋顶的遮挡。地形等级越高，坡度越陡，完全屏蔽是不合适的。

Calculating Wind Classification

Referring to TABLE 2 – WIND CLASSICATION FROM WIND REGION AND SITE CONDITIONS on Page 8, and following these 4 steps below, the wind classification for your site is able to be determined.

按照下面的4个步骤，可以确定您的场地的风分级。

From FIGURE 1 (Page 3): Determine your Geographic wind speed region, either A B C or D从图1(第3页):确定您的地理风速区域，A B C或D

From FIGURE 2 (Page 4): Determine the most appropriate terrain category (TC) for your site从图2(第4页):为您的站点确定最合适的地形类别(TC)

From FIGURE 3 (page 5): Determine the Topographic Class most relevant for your structure by calculating the slope of site at its maximum point and the location of the structure in terms if bottom,middle or top 1/3 of slopes height.

从图3(第5页):通过计算场地在其最大点处的坡度，以及根据斜坡高度的1/3(如底部、中部或顶部)来确定与您的结构最相关的地形类别。

From FIGURE 4 (Page 6) : Determine the Shielding most relevant to site from fully shielded FS partially shielded PS or not shielded NS from the prevailing wind direction.

从图4(第6页):确定与场地最相关的屏蔽:完全屏蔽FS部分屏蔽PS或未屏蔽NS，使其不受盛行风方向影响。