One of the most significant factors is the shear-span/depth ratio(剪跨比)a,/ho ,Shear span a,is defined as the distance between points of zero and maximum moments. d moment moment zero zero L moment maximum (a) (b) Fig.7.1-4 Shear span. (a)Geometry and loading;(b)bending moment• One of the most significant factors is the shear-span/depth ratio（剪跨比） , Shear span av is defined as the distance between points of zero and maximum moments. a / h0 v Fig. 7.1-4 Shear span. (a) Geometry and loading; (b) bending moment