Maximum shear force is 3/2 � F/a�a ( a = side of square)
= 3/2 � 94�10³/320�320
= 1.3769 N/mm².

In a thin cylindrical shell of internal radius r thickness t when subjected to internal fluid pressure P, stress developed in internal walls can be termed as circumferential stress or hoop stress.
P(h) = pr/t.

Shear stress at top flange of I section is zero.
Shear stress at junction of web and flange= B/b �F/8I (D²-d²).
Shear stress at bottom of flange = F/8I (D²-d²).
And shear force is maximum at neutral axis i.e F/8I �[B/b (D²-d²)+d²].

Maximum shear force is w�l/2
= 60+16�8 / 2
= 94 kN.

The allowable stress in cast iron is 5500 N/mm².

The stress corresponding to ultimate load is known as ultimate stress and stress corresponding to breaking point is known as breaking stress. In stress strain curve, ultimate stress is above breaking stress. Hence ultimate stress is greater than breaking stress.

The resistance offered by internal stress to shear is known as shearing stress. Shearing stress is zero at extreme fibres of beam. The bending stresses are maximum at extreme fibres of beam cross section.

For a triangular section subjected to a shear force, shear stress at neutral axis is
= 4/3 � average shear stress
= 4/3 � F/A/2 ; A = bh
= 8F/3bh.

Working stress method is based on elastic ory assuming reinforced concrete as elastic material. The stress strain curve of concrete is assumed as linear from zero at neutral axis to a maximum value at extreme fibre. In working stress method, members are designed for working loads such that stresses developed are within allowable stress.

The modulus of section is ratio of moment of inertia to distance of neutral axis.
Given y = 50 mm
I = 2.8�10⁶ mm⁴.
& Z = I/y = 2.8�10⁶ / 50
= 57.76 �10³ mm
= 57.7 ~ 58 m.