FREE BOOKS

Author's List




PREV.   NEXT  
|<   59   60   61   62   63   64   65   66   67   68   69   70   71   72   73   74   75   76   77   78   79   80   81   82   83  
84   85   86   87   88   89   90   91   92   93   94   95   96   97   98   99   100   101   102   103   104   105   106   107   108   >>   >|  
osition, of stresses takes place. The portion which is laid off below the bottom rods will probably not act unless there is sufficient concrete below the reinforcing bars and on the sides, and, as that is not the case in ordinary construction, it is very probable, as Mr. Goodrich has pointed out, that the concrete below the rods plays an unimportant part, and that the triangle which is now shown below the rod should be partially omitted. The triangles in Fig. 13 show the intensity of stress in the concrete at any point, or at any section where it is wanted. They show conclusively where the components are located in the concrete, their relation to the tensile stresses in the rods, and, furthermore, that they act only in a general way at right angles to one another. This is in accordance with the theory of beams, that at any point in the web there are tensile and compressive stresses of equal intensity, and at right angles to one another, although in a non-homogeneous web the distribution is somewhat different. After having found at the point of junction the intensity of stress, it is possible to tell whether or not a bond between the stirrups and the bottom rods is necessary, and it would not seem to be where the stirrups are vertical. It would also seem possible to tell in what direction, if any, the bend in the inclined stirrups should be made. It is to be assumed, although not expressly stated, that the bends should curve from the center up toward the end of the beam, but an inspection of the stress triangles, Fig. 13, will show that the intensity of stress is just as great on the opposite side, and it is probable that, if any bends were required to reduce the maximum stress in the concrete, they should as likely be made on the side nearest the abutment. From the stress triangles it may also be shown that, if the stirrups were vertical instead of inclined, the stress in the concrete on both sides would be practically equal, and that, in consequence, vertical stirrups are preferable. The next issue raised by the author is covered in his seventh point, and relates to bending moments. He states: "* * * bending moments in so-called continuous beams are juggled to reduce them to what the designer would like to have them. This has come to be almost a matter of taste, * * *." The author seems to imply that such juggling is wrong. As a matter of fact, it is perfectly allowable and legitimate in every instance o
PREV.   NEXT  
|<   59   60   61   62   63   64   65   66   67   68   69   70   71   72   73   74   75   76   77   78   79   80   81   82   83  
84   85   86   87   88   89   90   91   92   93   94   95   96   97   98   99   100   101   102   103   104   105   106   107   108   >>   >|  



Top keywords:

stress

 

concrete

 

stirrups

 
intensity
 
triangles
 

vertical

 

stresses

 
author
 

reduce

 

tensile


bending

 

moments

 

matter

 
inclined
 

angles

 

probable

 

bottom

 
practically
 

preferable

 
consequence

seventh

 
covered
 

raised

 

abutment

 
opposite
 

inspection

 

omitted

 

nearest

 

maximum

 

required


relates

 

portion

 

juggling

 

perfectly

 
instance
 

legitimate

 
allowable
 
osition
 
called
 

continuous


states

 

juggled

 

designer

 
compressive
 

Goodrich

 

theory

 

accordance

 
distribution
 

homogeneous

 
conclusively