Deflection of the Rigid Bar  
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The figure shows a vertical bar A B C which is pinned at B and supported by horizontal rods at A and C. The length of the segments A B and B C are 400 millimeters and 520 millimeters respectively. The rod at C is of length 2000 millimeters and the rod at A is of length 1250 millimeters. A load P directed to the right acts on the bar between B and C. The rod at A is compressed and the rod at C is stretched by 1.82 millimeters.

Based on the measured strain, the axial elongation of rod (1) must be +1.82 mm (i.e., the rod grows longer). Since rigid bar ABC is attached to rod (1), the rigid bar must deflect the same amount at point C.

Since the rigid bar is pinned at point B, the deflection of the rigid bar is zero at B. The pin does, however, permit the bar to rotate. Consequently, the deflection that occurs at C causes the bar to rotate into the position shown.