[b]Reinforcing existing joists.[/b] 1

[structural248]

I'm going over the example from the book "Designing with Steel Joists, Joist Girders and Steel Deck" by Fisher, West and Van de Pas, 1991.

Page 165: How did they calculate the tension in the end bar and the maximum compression rod?

Is there a simple way to detemine these forces other than a computer model of the entire joist.

Is there any other method books available for joist reinforcement?

 

[SperlingPE]

joists are trusses

 

[UcfSE]

Can you tell us what example or chapter it's in? I have the 2nd edition of that book and p165 is in the middle of the index.

I haven't heard of any other books for joist reinforcement. The one you have is very good imho. It's straight forward and the recommendations are simple and easy to implement in the field for the most part.

 

[structural248]

This is in Chapter 5 Joist Reinforcement.
Example 5.5.2 Joist reinforcement.

 

[UcfSE]

Using the measurements given you can find the angles between the webs and the horizontal. For the end bar I get arctan(20/39)=theta=27.15 deg. With the reaction being 5.93k, summing forces in vertical direction gives: end_bar*sin(27.15)=5.93k end_bar=13 kips which is about the answer they give. Doing the same you can get the horizontal chord force end_bar*cos(27.15)=hor_chord=11.56 kips. The angle between the first web and the horizontal is arctan(20/12)=phi=59 deg. The component of the horizontal force in the direction parallel to the web is 11.56*cos(59)=5.96 kips.