Drainage holes on the tower platform
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According to HG21543-92, a drainage hole with a diameter of φ17 must be provided every 1.4 square meters in the platform flooring. Why is it 17 and not some other number? Where does this value come from? Does anyone know?
It seems that no one knows the issue with the φ17 drainage hole; we look forward to experts conducting research on it.
Based on one hole per 1.4 square meters (with a hole diameter of d=17mm), an accumulated rainwater height of h=10mm, and rainfall of extreme intensity (24-hour rainfall of 500mm), it is necessary to determine whether this hole meets the requirements. First, the maximum allowable flow rate for the hole is calculated: the velocity through the hole is u=0.6*SQRT(2gh)=0.265631323 m/s. With a diameter of d=17mm, the corresponding area is S=0.000226865 m2. Thus, the flow rate through the hole is Q2=S*u=6.02625E-05 m3/s. The rainfall intensity during extreme storms is H=250mm/24h=0.020833333 m/h=5.78704E-06 m/s. Therefore, the rainfall volume per 1.4 square meters is Q1=1.4*H=8.10185E-06 m3/s. Hence, the hole meets the requirements even if it is partially blocked, resulting in a reduced diameter from 17mm to 7mm; in that case, the flow rate would still be Q2=1.02175E-05 m3/s, which is sufficient to meet the requirements. I’m not an expert, so the algorithm may not be correct.