CHAPTER V 

 Joints and Connections 



FIG. 85s was copied from a sheet of drawings forming part of 

 a set made for the building of a public school in a middle 

 western state. The writer knows from experience in check- 

 ing designs that this is a common type of roof. Amateur architects 

 and many young draftsmen have a fondness for constructing 

 wooden trusses with light tension members of wood. The 

 student who read Chapter IV carefully knows how simple a 

 Xst*effy matter it is to find 



I .composition ^of .;4 * 3 ' 5f "P j v chon(,& 8 - thestrcssesinthc 



I 



members of a simple 

 truss. There are many 

 hand-books on the 

 market which contain 

 diagrams and formu- 

 las for the design of 



nil/sses OH is rr. CCHTCKS 



Fig. SOB. 



trusses, so it is not a difficult thing to proportion the members 

 of any form of truss. 



The student is advised to check the design of the truss shown 

 in Fig. SOB. It will be a very useful exercise. The joists are on 

 16-in. centers. The joists under the roof are 2 in. x 8 in. and 

 carrying sheathing on which is placed the composition roofing. 

 The ceiling joists are 2 in. x 6 in. In the design assume a fiber 

 stress in tension and compression of 800 Ibs. per sq. in., the loads 

 per square foot of horizontal surface to be as follows: composition 

 roofing, 5 Ibs. ; joists, 5 Ibs.; sheathing, 4 Ibs.; plastering, 5 Ibs.; 

 roof load 30 Ibs. ; truss, 4 Ibs. 



In the specifications appeared the following clause: " The truss 

 is to be well and securely nailed together, but the number of nails 

 at each joint shall not be less than shown on the drawings." The 

 draftsman had placed eight dots at each joint, probably meaning 

 each dot to represent a nail. The size of nail to use was not given. 

 On the advice of the author the roof was changed so it appeared 



136 



