TREE SEARCH 



The tree search (Figure 5c) is given a node to start. It looks through all plate items 

 (both NH and NT) which have not yet been used to see if one joins the node. If not, it is by- 

 passed. If so, it looks at the node at the other end and determines if that node has been joined 

 to the tree. If not, it puts the new node on the tree by giving the value of NEXT for the new 

 node, the present node, and puts the new node on the bottom of the list of nodes to be searched, 

 NRANK. A value for LINK is given each node as it is entered on the tree, which tells which 

 plate goes back to NEXT. The sign of LINK specifies the direction of the plate. The branch 

 is put on the tree by making MTYPE = 1. If, when the other end of a branch is being examined 

 to see if it should be added to the tree, it is found that it is already on the tree (NEXT ^ 0), 

 then the branch is one that will close a loop and MTYPE = - 1.^ After all branches have been 

 examined to see if they touch the first node, the computer will take the next item on NRANK, 

 and if it is on the tree (NRANK 4^ 0), it will look through the remaining branches, etc. There 

 are two possible exits. Normal exit occurs if all nodes are found (it finds NN of them). If 

 all nodes are not connected, then, at some time all nodes which were connected to the first 

 node have been searched, but no more nodes are in NRANK to use. The computer prints a 

 statement if nodes are not properly connected, and starts to the next case. 



FIND TREE LOOPS 



To find the loops (Figure 5d), take each plate which is not on the tree (MTYPE = -1). 

 Go back down the tree from both ends to the origin to close loop. For symmetric sections, 

 shear flow can cross the centerline for z-shear and torsion but not for y-shear. More loops 

 are generated by going directly from the first node to the other nodes on the centerline and 

 then returning via the tree. L = number of loops for y-shear, LA = number of loops for z-shear 

 and torsion. 



The word NEXT was used in connection with going back down the tree to the first 

 node. 



OUTPUT 



Output may be either on-line (printer) or off-line (tape) by proper choice of sense 

 switch 5 (see output flow chart, Figure 3b). 



8.3 



