建筑屋面方形溢流口溢流量计算公式分析及探究

Calculation Formula of Overflow Flow of Square Overflow Orifice of Building Roof

建筑屋面溢流口的设计计算关系到屋面结构安全,对现有国家规范中墙体方形溢流口溢流量计算公式进行了分析对比,通过对水力学不同堰流形式、宽顶堰基本计算公式、流量系数及侧收缩系数等方面的分析推导,得出按现有规范公式计算出的溢流口几何尺寸偏小。结合屋面不同雨水斗对斗前水深的要求及建筑屋面的不同排水形式,提出了墙体方形溢流口属于宽顶堰,明确了溢流口的溢流水位高度和上游坎高度的取值范围,进而采用数学工具推出了屋面方形溢流口溢流量新的计算公式,并从水力学和数学角度对新公式进行了合理性分析,可供设计同行参考。

The design and calculation of overflow orifice of building roof is related to the safety of roof structure.The overflow flow calculation formulas of the square wall overflow orifice in the existing national norms are analyzed and compared.Through the analysis and deduction of different hydraulic weir flow forms,the basic calculation formulas of broad crested weir,the flow coefficient and the side shrinkage coefficient,it is concluded that the overflow orifice geometric size calculated according to the existing normative formula is smaller.Combined with the requirements of different roof drains on the water depth before the drain and the different drainage forms of building roof,it is proposed that the wall square overflow orifice belongs to the broad crested weir,and the value range of the overflow water level height of the overflow orifice and the height of the upstream wall is defined,and then a new calculation formula of the overflow flow of the roof square overflow orifice is introduced by using mathematical tools,and the rationality of the new formula is analyzed from the hydraulics and mathematical perspectives,which can be used as a reference for design colleagues.