# Gbchg

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GBCHG is the polygon for the joint, and since BC acts down (see the polygon) CH acts up and HG down. Therefore, place the proper arrowheads on eh and hg near (3), and record that the stresses in those members are compressive and tensile respectively. Measuring, we find that CH and HG scale 4,100 and 2,720 pounds respectively.

It is plain that the stress in any member on the right hand side is the same as that in the corresponding member on the left, hence it is not necessary to construct the complete stress diagram.

2. It is required to analyze the truss of Fig. 25 which rests on end supports and sustains three loads each of 2,000 pounds as shown. Each member is 16 feet long.

Evidently, reactions are each 3,000 pounds. Following directions of Art. 26, first letter the truss diagram and then draw a polygon for the loads and reactions representing them in either order in which they occur about the truss. DCBAED is a counter-clockwise polygon, DC, CB, and BA representing the loads at joints (1), (2) and (3), AE the left reaction, ED the right reaction.

The construction of the polygons is carried out as in the preceding illustration, and little explanation is necessary. The polygon for joint (4) is AEFA, EE (1,725 pounds tension) representing the stress in of and FA (3,450 pounds compression) that in of. The polygon for joint (3) is BAFGB, FG (1,150 pounds tension) representing the stress in fg and GB (2,000 pounds compression) that in yb. The polygon for joint (5) is GFEHG, EH (2,875 pounds tension) representing the stress in eh and IIG (1,130 pounds compression) that in leg.

Evidently the stress in any member on the right side of the truss is like that in the corresponding member on the left, therefore it is not necessary to construct the remainder of the stress diagram.

1. Analyze the truss represented in Fig. 26, it being sup ported at its ends and sustaining three loads of 2,000 and two of 1,000 pounds as represented.

2. Analyze the truss represented in Fig. 27, it being sup ported at its ends and sustaining five 2,000-pound loads and two of 1,000 as shown.