3 steel plates of 6 mm thickness, a total of 4 rivets, each 11 mm in diameter, at the corners of an equilateral triangle with one side 12√3 mm long (rivet no. 1, 2 and 3) and in the center of this triangle (rivet no. 4) are connected with each other. A force of 45000 N acts on the middle plate as in the figure. The safe shear stress for the rivet is 120 N/mm2 and the safe surface pressure is 225 N/mm2. According to this;
a) Show all the forces acting on each rivet by drawing them on the figure, showing their directions.
b) Make the safety checks by specifying the number of rivets that have the most difficulty.
 

45000 N + 2 1 + + 4 + 3 +