基于Copula函数的海绵城市日气温设计

极端温度和温差影响混凝土微观结构特征和力学性能,气温被视作混凝土施工维养的重要设计依据。基于中国819个气象站1961—2015年日气象和地理信息资料,采用地统计方法和Copula函数对海绵城市进行气象分区,分析分区日均温和日温差边际、联合概率分布,设计日均温、日温差和相应混凝土抗压强度。结果表明:海绵城市气象分区与行政分区一致;各分区日均温和日温差多服从正态分布,冬、夏日均温期望值在0～13.6℃和23.2～26.4℃间变化、标准差在3.2～5.4℃和2.5～3.5℃间变化,冬、夏日温差期望值在7.4～12.1℃和7.4～11.8℃间变化、标准差在2.9～3.7℃和1.8～3.4℃间变化;日均温和日温差联合概率分布冬季对称,夏季不对称,相应AMH Copula函数参数值分别在-5.68×10~(-6)～4.93×10~(-6)和-6.37×10~(-6)～4.89×10~(-6)间变化;冬季,东北、华北和西北分区设计频率分别处于50%、5%、5%,低于国标设计温度,设计出的混凝土无法达到抗冻要求,其余分区设计频率在国标设计温度内满足设计要求;夏季,各分区日均温均高于混凝土国标养护温度,易使得混凝土内外温度失调而产生热胀破坏。设计的极端温度、温差及抗压强度是对现有国标混凝土养护温度的补充和完善,为海绵城市新性能混凝土构建提供科学依据。

Copula function-based design of daily temperature for sponge city

Extreme temperature and temperature difference affect the microstructural characteristics and mechanical properties of concrete. Based on the daily meteorological and geographic information data from 1961 to 2015 from 819 meteorological stations in China，the meteorological zoning for sponge city is made with geostatistical method and Copula function，and then the marginal and joint probability distributions of the zonal daily mean temperature ( T) and temperature difference ( ΔT) ，the design daily mean temperature ( T) and daily temperature difference ( ΔT) as well as the corresponding compressive strength of concrete are analyzed herein. The result shows that the meteorological zoning is consistent with the administrative zoning. The daily mean temperature ( T) and daily temperature difference ( ΔT) of most of all the subzones are subject to the normal distribution; for which the expected values of the daily mean temperatures ( T) in winter and summer change from 0 to 13. 6 ℃ with the standard deviationsof 3. 2 ～5. 4 ℃ and 2. 5 ～ 3. 5 ℃，while the expected values of the temperature differences ( ΔT) in winter and summer change from 7. 4° to 12. 1° and from 4 to 11. 8 ℃ with the standard deviations of 2. 9 ～3. 7 ℃ and 1. 8 ～3. 4 ℃. Both the joint probability distributions of the daily mean temperature ( T) and the daily temperature difference ( ΔT) are symmetrical in winter and asymmetrical in summer respectively，while the parameters of AMH Copula function range from －5. 68 to 4. 93 ×10 －6 and －6. 37 to 4. 89 × 10 －6 in winter and summer respectively. In winter，the design frequencies of the subzones，i. e. Northeast China，North China and Northwest China are 50%，5% and 5% respectively，which are lower than the design temperature of the national standard，from which the designed concrete cannot meet the relevant freezing resistance requirement. However，the design frequencies of the other subzones are within the national standard of the design temperature and then can meet the design requirement concerned. In summer，the daily mean temperatures ( T) of all the subzones are higher than the curing temperature defined in the national standard for concrete，which are prone to make offset of temperature inside and outside concrete and then cause thermal expansion damage. The designed extreme temperature，temperature difference and compressive strength are the supplement and modification to the curing temperature of concrete defined in the relevant current national standard，thus provide the scientific basis for the construction of sponge city with new-performance concrete.