Free-Body Diagram at Flange B  
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The figure shows the free body diagram around flange B. The free body diagram cuts through members 1 and 2. The load on the flange is P which equals 110 kilo newtons directed vertically downwards. The reaction force on member 1 is F subscript 1 directed vertically upwards.

To solve this problem, first consider equilibrium. Draw a free-body diagram around flange B.

Assume that the internal force in member (1) is tension.