福建沿海历史街区风荷载特性数值模拟与风险防控方法
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摘要
通过ANSYS Fluent软件选用RNG k-ε湍流模型,以福建沿海历史街区为对象,数值计算分析街道形态与路网形式对极值风压系数分布的影响并探讨风灾防控的策略。研究表明:单一街道在全风向下高宽比(1.33)产生爬越流时极值负压系数绝对值较大,最大负压系数绝对值产生于风向与街道垂直且高宽比最大(1.33)的条件下;随风向由垂直于街道变为平行,多条街道相交与单一街道风压系数变化一致:整体的正、负压系数绝对值和范围均大幅度降低,单一街道、同一高宽比的极值负压系数绝对值最大降低64.74%,平均降低了43.93%。对三坊七巷与和平路历史街区造成风致破坏的最重要因素是临近历史街区的高层建筑带来的极值正压与负压系数,其次为开敞空间与街区道路走向。极值负压系数绝对值在建筑间距/高度3.5～5.8时成正相关,拟合曲线为抛物线,在建筑间距/高度大于5.8时极值负压系数绝对值均趋于稳定值。当风向与方格路网垂直时,高密度低矮建筑的风荷载极值与建筑所在的道路走向(平行或垂直)不相关。历史街区的风灾防控可从绿化配置和建设控制地带建筑优化两方面实现。
Based on ANSYS Fluent software the RNG k-ε turbulence model was selected in the research. The coastal historic district of Fujian were chosen as research object and the influence of street pattern and road net form on the distribution of extreme wind pressure coefficients was analyzed numerically, and the strategy of wind disaster prevention and control was discussed. The research shows that: The absolute value of the extreme negative pressure coefficient is larger when aspect ratio(1.33)of a single street produces a cross flow at the full wind direction. The absolute value of the maximum negative pressure coefficient generated in the condition of wind direction perpendicular to the street and the maximum aspect ratio(1.33). The change of wind pressure coefficient of intersection of multiple streets is consistent with a single street as the wind direction changes from perpendicular to street to parallel: the absolute value of the overall positive and negative pressure coefficients and range are greatly reduced, and the absolute value of the extreme negative pressure coefficient of a single street in the condition of the same aspect ratio is reduced by a maximum of 64.74% and an average reduction of 43.93%. The most important factor causing wind damage to Sanfangqixiang and Hepinglu historic districts is the extreme positive pressure and negative pressure coefficients brought by high-rise buildings near the historical block, followed by the open space in the district and the street road direction. The absolute value of the extreme negative pressure coefficient is positively correlated when the building's spacing/height is 3.5-5.8, and the fitting curve is a parabola. When the building's aspect ratio is greater than 5.8, the absolute value of the extreme negative pressure coefficient tends to a stable value. When the wind direction is perpendicular to the square road net, the wind load extremes of the high-density and low-rise buildings are not related to the road direction(parallel or vertical) of the building. The prevention and control of wind disaster in historic districts can be achieved from two aspects of greening configuration and architecture optimization in zone of construction needs to be controlled.
Based on ANSYS Fluent software the RNG k-ε turbulence model was selected in the research. The coastal historic district of Fujian were chosen as research object and the influence of street pattern and road net form on the distribution of extreme wind pressure coefficients was analyzed numerically, and the strategy of wind disaster prevention and control was discussed. The research shows that: The absolute value of the extreme negative pressure coefficient is larger when aspect ratio(1.33)of a single street produces a cross flow at the full wind direction. The absolute value of the maximum negative pressure coefficient generated in the condition of wind direction perpendicular to the street and the maximum aspect ratio(1.33). The change of wind pressure coefficient of intersection of multiple streets is consistent with a single street as the wind direction changes from perpendicular to street to parallel: the absolute value of the overall positive and negative pressure coefficients and range are greatly reduced, and the absolute value of the extreme negative pressure coefficient of a single street in the condition of the same aspect ratio is reduced by a maximum of 64.74% and an average reduction of 43.93%. The most important factor causing wind damage to Sanfangqixiang and Hepinglu historic districts is the extreme positive pressure and negative pressure coefficients brought by high-rise buildings near the historical block, followed by the open space in the district and the street road direction. The absolute value of the extreme negative pressure coefficient is positively correlated when the building's spacing/height is 3.5-5.8, and the fitting curve is a parabola. When the building's aspect ratio is greater than 5.8, the absolute value of the extreme negative pressure coefficient tends to a stable value. When the wind direction is perpendicular to the square road net, the wind load extremes of the high-density and low-rise buildings are not related to the road direction(parallel or vertical) of the building. The prevention and control of wind disaster in historic districts can be achieved from two aspects of greening configuration and architecture optimization in zone of construction needs to be controlled.
引文
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[2] 殷志祥,李军,张爽. 体育场馆建筑群风荷载相互干扰效应数值模拟研究[J]. 工程力学,2015,32(S1):289-293.
[3] LI Gang, GAN Shi, LI Yongxin, et al. Wind-induced interference effects on low-rise buildings with gable roof [J]. Journal of Wind Engineering and Industrial Aerodynamics, 2017(11):94-106.
[4] Hatem Alrawashdeh, Ted Stathopoulos. Wind pressures on large roofs of low buildings and wind codes and standards[J]. Journal of Wind Engineering and Industrial Aerodynamics, 2015(12): 212-225.
[5] GA Kopp, C Mans, D Surry. Wind effects of parapets on low buildings: part 4. Mitigation of corner loads with alternative geometries[J]. Journal of Wind Engineering and Industrial Aerodynamics, 2005, 93(11): 873-888.
[6] 汪汛,周岱,李煜,等. 重檐歇山顶中国古建筑风压与风场数值模拟分析[J]. 上海交通大学学报,2017,51(11):1287-1296.
[7] 单文姗. 殿堂式中国古建筑屋面风荷载特性[D]. 北京:北京交通大学,2016.
[8] 魏应植. 影响福建台风的路径、灾害和风雨特征研究[C] //广州:中国气象学会学术年会论文集,2007: 394-403.
[9] 雷鹰,李涛,张建国,等. 厦门地区台风风场特性的数值模拟[J]. 工程力学,2014 (1):122-128.
[10] Oke T R. Street design and urban canopy layer climate[J]. Energy and buildings,1988,11(1):103-113.
[11] CH Chang, RN Meroney. Concentration and flow distributions in urban street canyons: wind tunnel and computational data [J]. Journal of Wind Engineering and Industrial Aerodynamics, 2003, 91(9): 1141-1154.
[12] 李波,杨庆山,徐志,等. 树木对低矮房屋风荷载的遮挡作用[J]. 建筑结构学报, 2016, 37(S1): 33-38.
[13] 王焱. 夏热冬冷地区住宅节能优化设计[D]. 南京:东南大学, 2003.