200 



PRACTICAL STRUCTURAL DESIGN 



multiplied by the perpendicular distance between these two 

 lines of action. 



Each rivet in the group carries an amount of direct stress as 

 shear equal to the total load divided by the number of rivets. 



STATICAL MOMENT ABOUT 

 AXIS xx' 





STATICAL MOMENT ABOUT 

 AXIS yy' 



Total Area 

 Total M 



f = 



5A 



A(2d + e) 



A(2d+e) 

 5A 



Total Area 

 Total M 



5A 



A(a + b + 2c) 



A(a +b + 2c) 

 5A 



Fig. 117. Method of Moments to find Center of Gravity of Group of Rivets. 



If the direct application of the load causes a bending moment, 

 then each rivet has an added stress due to bending moment. 



The stress in any rivet due to bending moment varies directly 

 as its distance from the center of gravity of the group of 

 rivets, and its resisting moment varies as the square of this 

 distance. 



Fig. 118 represents an angle connection for the end of a 10-in. 

 I-beam weighing 25 Ibs. per lineal foot. The reaction from the 

 load carried on the beam is 13,720 Ibs. delivered to the leg out- 

 standing from the beam, the other leg being connected to the 

 web of the beam. Finding the center of gravity of the three 

 rivets and multiplying we get an eccentric bending moment, 



M = 13,720 x 3.25 = 56,290 in. Ibs. 



