Timber rafter ceiling joist connection 8

[Calc1]

I am using method of joints to calculate the tension force in ceiling joist but the result is 2 times the computer run or any roof framing book table, anyone has any suggestions, for example if uniform load is 54 lb/ft for LD=1 on the rafter(Horz) and the span is 17 ft with 1 ft overhang each side, the reaction at the wall = 459 lbs, the ceiling joist tension force=T=1377 lbs now if you use any framing book, they recommend 6-16d nail which capacity is 1/2 around 650 lbs which is close to computer run result, am I missing something here?

 

[Calc1]

Thanks everyone for participating, I am glad that such a fundamental case is resolved, I know that many in our field did not have a answer for this case, even those who I have opportunity to work with in this field, but again, I appreciate everyone inputs and sharing their knowledge. I have had many conflicting answers, from Residential Structural Design Guide: 2000 Edition (HUD2000 edition), design example 7.3 (Heel Joint) that used joint method and designed for higher tension load to structural exam (SE) sample problem that tension force was the lesser value based on FBD and take the moments around the ridge.

 

[pba]

SlideRuleEra,

Thanks for the new slides. Yes you are correct! To my horror I must confirm that I've designed a great number of cut timber roofs with twice the necessary ceiling tie tension load. I am at least grateful that I've designed for twice and not half...

 

[SacreBleu]

SlideRuleEra...
Thanks- I have seen the light. It is with some amount of amazement that I thought the world was flat...for a while.

 

[miecz]

Three cheers for apsix for holding his/her ground in the face of formidable opposition, and to Calc1 for bringing up the issue in the first place.