推荐回答（1个）
给你一个大六角高强螺栓的长度计算办法：
高强度螺栓的长度L应符合设计要求或按下式计算确定：
L=L′+△L (1)
式中 L′───连接板层总厚度（mm）；
△L ───附加长度（mm），
△L=m+2s+ip (2)
其中 m───高强度螺母公称厚度（mm）；
s───高强度垫圈公称厚度（mm）；
i───当L≤100mm时，i=2；当L＞100mm时，i=3；
p───螺纹的螺距（mm）。
表4.2.12 高强度螺栓附加长度△L（mm）
螺栓公称直径 M12 M16 M20 M22 M24 M27 M30
高强度螺母公称厚度 12.0 16.0 20.0 22.0 24.0 27.0 30.0
高强度垫圈公称厚度 3.0 4.0 4.0 5.0 5.0 5.0 5.0
螺纹的螺距 1.75 2.0 2.5 2.5 3.0 3.0 3.5
大六角头高强度螺栓附加长度 23.0 30.0 35.5 39.5 43.0 46.0 50.5
根据公式（1）计算所得值，当L≤100mm时，可按螺栓长度以5mm为一个规格的规定，将其个位数按2舍3入、7舍8入的原则，计算出使用长度；当L＞100mm时，可按螺栓长度以10mm为一个规格的规定，将其个位数按4舍5入的原则，计算出使用长度。
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