Construction of Barn Frames. 339 



the stronger members. (2) That of shortening the free 

 span. 



The first case is illustrated in the rows of bridging used 

 between the joists in a floor. In these cases when a weak 

 member is bridged between two stronger ones a portion of 

 its load, because it yields soonest, is thrown by the bridging 

 upon the stronger, and stiffer floors are thus secured and 

 the breaking of individual pieces prevented. 



Braces in nearly all cases are, in principle, either posts 

 or else they are suspension rods which allow the strength of 

 the material to be utilized unaffected by the principle of 

 leverage, the stress being a direct pull or. a push, bringing 

 into play the full tensile or crushing strength of the ma- 

 terial. 



To shorten the free span of an 18-foot joist or timber 

 two feet at each end by means of suitable braces is in- 

 creasing its carrying power 28.5 per cent. 



It is much more important to pay strict attention to these 

 matters of strength at the present time than in former years 

 both because lumber is higher and often of much inferior 

 quality. 



415. Constructing Timbers from Two-inch Lumber. It is 



often not only cheaper but better to construct 8x10 or 8x12 

 beams by putting together 2x10 or 2x12 plank, the timber 

 thus constructed of ten being stronger than a solid one would 

 be because weak places are more likely to be distributed so 

 as to give a greater mean strength. It is of course not true 

 that a 10x10 so made would be stronger than a solid timber 

 of the same dimensions if both were of highest grade 

 lumber. 



416. Form of Barn Frame. During pioneer days, when 

 saw mills were none or few, it was much easier to secure the 

 needed stability for a barn by hewing a few heavy timbers 

 of suitable length and putting them together with braces 

 than it was to use the 2 inch lumber now so common in the 

 frames of dwelling houses. 



Since the old type of barn frame was depended upon to 



