設T形截面翼緣寬b,翼緣厚t,腹板高hw,腹板厚tw。以翼緣上邊緣為基準線,按求形心公式,y=ΣAiyi/ΣAi 計算:
y=[(bt)(t/2)+(hwtw)(hw/2+t/2)]/(bt+hwtw)
=[(bt^2)/2+(hwtw)(hw+t)/2]/(bt+hwtw)
故形心在對稱軸y軸上,距翼緣上邊緣向下距離按上式y值確定。