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1. 技术说明
2. 载入中
3. 标志的风荷载计算 – 在 1991

# 标志的风荷载计算 – 在 1991

## 结构数据

 位置 Oxfordshire, 英国 占用 各种各样的 – 招牌 地形 平坦的农田 Sign Horizontal Dimension, b 12.0 米 Sign Horizontal Vertical, H 12.0 米 Ground to top of signboard, H 50.0米 Ground to signboard centroid, 与Ë 44.0 米 Reference area of signboard A标志 144.0 平方米. Pole diameter, d 1.0 米 Pole surface type Cast iron Ground to top of pole, 与G 38.0 米 Reference area of pole Apole 38.0 米  $${v}_{b} = {C}_{给你} {C}_{季节} {C}_{alt} {v}_{b,map}$$ (1)

$${v}_{b}$$ = 以 m/s 为单位的基本风速
$${C}_{给你}$$ = directional factor
$${C}_{季节}$$= 季节性因素
$${C}_{alt}$$= altitude factor where:

$${C}_{alt} = 1 + 0.001一个$$ 对于 $$z ≤ 10$$ (2)
$${C}_{alt} = 1 + 0.001一个 ({10/与}^{0.2})$$ 对于 $$与 > 10$$ (3)

$${v}_{b,map}$$ = fundamental value of the basic wind velocity given in Figure NA.1 of BS EN 1991-1-4 National Annex
$$一个$$ = altitude of the site in metres above mean sea level

$${q}_{b} = 0.5 {⍴}_{空气} {{v}_{b}}^{2}$$ (4)

$${q}_{b}$$ =设计风压Pa
$${⍴}_{空气}$$ = density of air (1.226公斤/立方米)
$${v}_{b}$$= 以 m/s 为单位的基本风速

$${q}_{p}(与) = 0.5 {C}_{Ë}(与){q}_{b}$$ for site in Country terrain (5)
$${q}_{p}(与) = 0.5 {C}_{Ë}(与){C}_{Ë,Ť}{q}_{b}$$ for site in Town terrain (6)

$${C}_{Ë}(与)$$ 雪地装载
$${C}_{Ë,Ť}$$ = exposure correction factor for Town terrain

To calculate the wind force acting on the signboard/pole:

$${F}_{w} = {C}_{s}{C}_{d}{C}_{F}{q}_{p}({与}_{Ë}){一个}_{ref}$$ (7)

$${C}_{s} {C}_{d}$$ = structural factor
$${C}_{F}$$ = force coefficient of the structure
$${q}_{p}({与}_{Ë})$$ = peak velocity pressure at reference height $${与}_{Ë}$$
$${一个}_{ref} = b h$$ = reference area of the structure

## 地形类别

Based on BS EN 1991-1-4 National Annex, the Terrain Categories in EN 1991-1-14 were aggregated into 3 类别: Terrain category 0 is referred to as Sea; Terrain categories I and II have been considered as Country terrain, and Terrain categories III and IV have been considered as Town terrain.

Considering wind coming from 240°, we can classify the terrain category of the upwind terrain as Town terrain.

## Directional and Season Factors, $${C}_{给你}$$ & $${C}_{季节}$$ ## Altitude Factor $${C}_{alt}$$

For the altitude factor, $${C}_{alt}$$, we will only use Equation (2) for a more conservative approach using site elevation $$一个$$ equal to 57.35m. 因此:

$${C}_{alt} = 1 + 0.001(57.35) = 1.05735$$

## 基本风速和压力, $${v}_{b}$$ & $${q}_{b}$$

The wind speed map for the United Kingdom can be taken from Figure NA.1 of the National Annex for BS EN 1991-1-4. $${v}_{b} = {C}_{给你} {C}_{季节} {C}_{alt} {v}_{b,map} = (1.0)(1.0)(1.05735)(22.7)$$
$${v}_{b} = 24.0 小姐$$

We can calculate the basic wind pressure, $${q}_{b,0}$$, 使用方程 (4):

$${q}_{b} = 0.5(1.226)({24}^{2}) = 353.09 出色地$$

SkyCiv现在可以自动检测风域并仅需少量输入即可获得相应的风速值. 试试我们的 SkyCiv自由风工具

## Orography Factor $${C}_{的}(与)$$

altitude factor, $${C}_{alt}$$, we will only use Equation (2) for a more conservative approach using site elevation $$一个$$ equal to 57.35m. 因此:

## Peak Velocity Pressure, $${q}_{p}(与)$$

For our structure, since the terrain category is classified as Town terrain, the peak Similarly, the peak velocity pressure, $${q}_{p}(与)$$, can be solved using Equation (6):

$${q}_{p}(与) = {C}_{Ë}(与){C}_{Ë,Ť}{q}_{b}$$

$${C}_{Ë}(与)$$ = exposure factor based on Figure NA.7 of BS EN 1991-1-4 National Annex
$${C}_{Ë,Ť}$$ = exposure correction factor for Town terrain based on Figure NA.8 of BS EN 1991-1-4 National Annex

To determine the exposure factor, $${C}_{Ë}(与)$$ , for the signboard, 我们需要计算 $$与 – {H}_{dis}$$ and the distance upwind to shoreline in km. For simplicity, we will set the the displacement height, $${H}_{dis}$$, 至 0. 为了 $$与$$ 价值观, we will consider it on $$z = 38.0$$ 和 $$z = 44.0$$. 此外, the distance upwind to shoreline is more than 100km. 因此, using Figure NA.7 of BS EN 1991-1-4 National Annex: $${C}_{Ë}(38.0) = 3.2$$
$${C}_{Ë}(44.0) = 3.3$$ $${C}_{Ë,Ť}(38.0) = 1.0$$
$${C}_{Ë,Ť}(44.0) = 1.0$$

Using the values above, we can calculate the peak velocity pressure, $${q}_{p}(与)$$, 对于 $$z = 38.0$$ 和 $$z = 50.0$$:

$${q}_{p}(44.0) = (3.3)(1.0)(353.09) = 1165.20 出色地$$
$${q}_{p}(38.0) = (3.2)(1.0)(353.09) = 1129.89 出色地$$

## Structural Factor, $${C}_{s}{C}_{d}$$

For our signboard, we will use simplified value for the structural factor, $${C}_{s}{C}_{d}$$, to be equal to 1.0 可以假设为 6 或AND 1991-1-4.

## Force Coefficient, $${C}_{F}$$, for signboard

For signboards, the force coefficient, $${C}_{F}$$, 等于 1.8 可以假设为 7.4.3 或AND 1991-1-4.

## Wind Force, $${F}_{w,signboard}$$, acting on the signboard

The force acting on the signboard can be calculated using Equation (7) 可以假设为 5.3(2) 或AND 1991-1-4.

$${F}_{w,signboard} = {C}_{s}{C}_{d}{C}_{F}{q}_{p}({与}_{Ë}){一个}_{ref,signboard} = (1.0)(1.8)(1165.20出色地)(12.0米)(12.0米)$$
$${F}_{w,signboard} = 302019.84 N$$

Note that the horizontal eccentricity of this wind force acting on the centroid of the signboard is recommended to be equal to 3.0m.

The wind calculations can all be performed using SkyCiv Load Generator for EN 1991 (signboard and pole wind load calculator). 我们将插入已知值, 我们将插入已知值. 我们将插入已知值, you can streamline this process and get a detailed wind load calculation report for signboards and poles!

## Wind Force, $${F}_{w,pole}$$, acting on the pole

$${F}_{w,pole} = {C}_{s}{C}_{d}{C}_{F}{q}_{p}({与}_{G}){一个}_{ref,pole}$$ (8)

$${C}_{F} = {C}_{F,0}{ψ}_{λ}$$
$${一个}_{ref,pole} = {与}_{G}d$$

$$ψ_{λ}$$ is calculated based on effective slenderness, $$λ$$, using using Figure 7.36 的部分 7.13 或AND 1991-1-4
$${C}_{F,0}$$ is calculated based on Reynolds number $$R_{Ë}$$ = 考虑到高于当地地形高度时加速减少的因素 7.28 或AND 1991-1-4

$${与}_{G}$$ is the height of the pole from the ground in m
$$d$$ is the diameter of the pole in m
$$ν = 0.000015 sq.m/s$$ is the kinematic viscosity of the air
$$v({与}_{G}) = (2{q}_{p}({与}_{G})/ρ)^{0.5}$$ (9)
$${[R}_{Ë} = v(z_{G})d/ ν$$ (10)

We will dive deep into these parameters on the next sections

## Reynolds number, $${[R}_{Ë}$$, for the pole

Using the calculated values above, we can calculate $$v({与}_{G})$$ 使用方程式 (9):

$$v({与}_{G}) = (2{q}_{p}({与}_{G})/ρ)^{0.5} = (2(1129.89)/(1.226))^{0.5}$$
$$v({与}_{G}) = 42.93 m/s$$

$${[R}_{Ë} = v({与}_{G})d/ ν = (42.93)(1.0)/(0.000015)$$
$${[R}_{Ë} = 2862000$$

## Force coefficient, $${C}_{f0}$$, without free-end flow

The pole material we used is cast-iron which has equivalent surface roughness $$ķ$$ 我们将插入已知值 0.2 基于表 7.13 或AND 1991-1-4. The force coefficient $${C}_{f0}$$ can be determined using the formula from Figure 7.28 EN 的 1991-1-4 与 $$k/d = 0.2$$:

$${C}_{f0}= 1.2 + {0.18日志(10 千/天)}/{1 + 0.4日志({[R}_{Ë}/{10}^{6}} = 1.2 + {0.18日志(10 (0.2)}/{1 + 0.4日志((2862000)/{10}^{6}}$$
$${C}_{f0} = 1.246$$

## 有效的纤细度, $$λ$$

$$λ = max(0.7 {与}_{G}/d, 70)$$ 对于 $${与}_{G}$$ > 50米
$$λ = max({与}_{G}/d, 70)$$ 对于 $${与}_{G}$$ < 15米 $${与}_{G} = 38$$
$${λ}_{50米} = max(0.7 (38), 70) = 70$$
$${λ}_{15米} = max((38), 70) = 70$$

$$λ = 70$$

## End-effect Factor, $${ψ}_{λ}$$

The end-effect factor, $${ψ}_{λ}$$, can be obtained using Figure 7.36 或AND 1991-1-4 requiring the solidity ratio $$披$$ and effective slenderness $$λ$$. We will assume solidity ratio $$披$$ 我们将插入已知值 1.0 since the pipe column does not have any perforation. From the calculated parameters above,we can already calculate the Wind Force, $${F}_{w,pole}$$:

$${C}_{F} = {C}_{F,0}{ψ}_{λ} = (1.246)(0.910) = 1.134$$

$${F}_{w,pole} = {C}_{s}{C}_{d}{C}_{F}{q}_{p}({与}_{Ë}){一个}_{ref,pole} = (1.0)(1.134)(1129.89)(38.0×1.0)$$
$${F}_{w,pole} = 48689.22 ñ$$  # SkyCiv负载生成器  You can check the detailed wind load report for the signboard thru these links: ## 参考资料:

• 在, 乙. (2005). 欧洲规范 1: 对结构的操作 - 第 1-4 部分: 一般作用——风作用.
• BSI. (2005). BS EN 1991-1-4: 2005+ A1: 2010: 欧洲规范 1. Actions on structures. General actions. 风动作.