Chapter 4 Wind Load 4.1 Background information of wind 4.2 Wind pressure 4.3 Height variation factor of wind pressure 4.4 Shape factor of wind load 4.5 Along-wind effect on structure 4.6 Cross-wind effect on structure 4.7 Wind load for bridge 归东理王大军 SHANDONG UNIVERSITY OF TECHNOLOGY
Chapter 4 Wind Load 4.1 Background information of wind 4.2 Wind pressure 4.3 Height variation factor of wind pressure 4.4 Shape factor of wind load 4.5 Along-wind effect on structure 4.6 Cross-wind effect on structure 4.7 Wind load for bridge
4.1 Background information of wind风的有关知识 Cause of wind风的形成 Wind is caused by differences in the atmospheric pressure.When a difference in atmospheric pressure exists,air moves from the higher to the lower pressure area,resulting in winds of various speeds.On a rotating planet,air will also be deflected by the Coriolis effect(柯氏效应)，except exactly on the equator.Globally,the two major driving factors of large-scale wind patterns (the atmospheric circulation)are the differential heating between the equator and the poles (difference in absorption of solar energy leading to buoyancy forces)and the rotation of the planet. 北极 图3.1大气热力学环流模型 赤道 的东理王大军 SHANDONG UNIVERSITY OF TECHNOLOGY
4.1 Background information of wind 风的有关知识 • Cause of wind 风的形成 ▫ Wind is caused by differences in the atmospheric pressure. When a difference in atmospheric pressure exists, air moves from the higher to the lower pressure area, resulting in winds of various speeds. On a rotating planet, air will also be deflected by the Coriolis effect(柯氏效应), except exactly on the equator. Globally, the two major driving factors of large-scale wind patterns (the atmospheric circulation) are the differential heating between the equator and the poles (difference in absorption of solar energy leading to buoyancy forces) and the rotation of the planet. 图3.1 大气热力学环流模型
4.1 Background information of wind风的有关知识 ·Three major types of wind三类性质的大风 Typhoon台风 A typhoon is a mature tropical cyclone that develops between 180 and 100E in the Northern Hemisphere.This region is referred to as the Northwestern Pacific Basin,and is the most active tropical cyclone basin on Earth,accounting for almost one-third of the world's annual tropical cyclones. In the Atlantic,Caribbean and eastern North Pacific,Hurricanes is used while in the Western Pacific and the South China Sea,typhoon is called. 归东理王大军 SHANDONG UNIVERSITY OF TECHNOLOGY
4.1 Background information of wind 风的有关知识 • Three major types of wind 三类性质的大风 ▫ Typhoon 台风 A typhoon is a mature tropical cyclone that develops between 180° and 100°E in the Northern Hemisphere. This region is referred to as the Northwestern Pacific Basin, and is the most active tropical cyclone basin on Earth, accounting for almost one-third of the world's annual tropical cyclones. In the Atlantic, Caribbean and eastern North Pacific, Hurricanes is used while in the Western Pacific and the South China Sea, typhoon is called
4.1 Background information of wind风的有关知识 ·Three major types of wind两类性质的大风 ·Monsoon季风 Seasonal wind between land and sea. Fundamental reason:thermal characteristics of earth surface Thunderstorm雷暴 ·Thermal Convective thunderstorm热对流雷暴 ·topographical thunderstorm地形性雷暴 ·frontal thunderstorm锋面雷暴 的东理王大军 SHANDONG UNIVERSITY OF TECHNOLOGY
4.1 Background information of wind 风的有关知识 • Three major types of wind 两类性质的大风 ▫ Monsoon 季风 Seasonal wind between land and sea. Fundamental reason: thermal characteristics of earth surface ▫ Thunderstorm 雷暴 Thermal Convective thunderstorm 热对流雷暴 topographical thunderstorm 地形性雷暴 frontal thunderstorm 锋面雷暴
4.1 Background information of wind风的有关知识 General conditions of wind climate in China我国风气候总况 1. 台湾、海南和南海诸岛由于地处海洋，常年受台风的直接影响，是我国最大的风 2. 东南沿海地区由于受台风影响，是我国太陆的大风区。，风速梯度由沿海指向内陆。 台风登陆后，受地面摩擦的影响，风速削弱很快。统计表明，在离海岸100k处， 风速药减小一半。 3. 东北、华北和西北地区是我国的次大风区，风速梯度由北向南，与寒潮入侵路线 致。 北地区夏季受季风影响，风速有可能超过寒潮风速。黑龙江西北部处于 我国纬度最北地区，它不在蒙古高压的正前方，因此那里的风速不大。 4. 青藏高原地势高，平均海拔在4~5km,属较大风区。 5. 长江中下游、黄河中下游是小风区，一般台风到此已大为减弱，寒潮风到此也是 强骜之末。 6. 云贵高愿处于东亚大气环流的死角，空气经常处于静止状态，加之地形闭塞，形 成了我国的最小风区。 归东罪子大军 SHANDONG UNIVERSITY OF TECHNOLOGY
4.1 Background information of wind 风的有关知识 • General conditions of wind climate in China 我国风气候总况 1. 台湾、海南和南海诸岛由于地处海洋，常年受台风的直接影响，是我国最大的风 区。 2. 东南沿海地区由于受台风影响，是我国大陆的大风区。风速梯度由沿海指向内陆。 台风登陆后，受地面摩擦的影响，风速削弱很快。统计表明，在离海岸100km处， 风速约减小一半。 3. 东北、华北和西北地区是我国的次大风区，风速梯度由北向南，与寒潮入侵路线 一致。华北地区夏季受季风影响，风速有可能超过寒潮风速。黑龙江西北部处于 我国纬度最北地区，它不在蒙古高压的正前方，因此那里的风速不大。 4. 青藏高原地势高，平均海拔在4～5 km，属较大风区。 5. 长江中下游、黄河中下游是小风区，一般台风到此已大为减弱，寒潮风到此也是 强弩之末。 6. 云贵高原处于东亚大气环流的死角，空气经常处于静止状态，加之地形闭塞，形 成了我国的最小风区