|
||||||||||||
|
||||||||||||
| Residential Beam Load Question | |||
| Post Reply | Forum | ||
| Posted by: malagodi ® 01/12/2006, 19:48:41 Author Profile eMail author Edit |
Hi, I have a BS in ME, but have been outside engineering for 20 years so I'm a bit rusty. Any help is greatly appreciated. We are removing a lolly column in a basment. The resulting span will be 10 ft. I plan to sister the existing wood beam (triple 2x10s) with two 1/2" x 8" x 11' steel plates (ASTM A36-A50 duel grade steel). The plates will be mounted on either side of the existing beam and the assembly will be staggered-drilled every 12" to accept 3/4" rod with washers and nuts. It is a two story cape. I'm estimating 40 psf live load and 15 psf dead load (total 55 psf) for each floor and I have calculated 1/2 the distance to the foundation on each side of the beam and came up with a total load of 13,750 lbs (or 1,375 lbs per linear foot). I haven't been able to find lots of info on the steel (my handbooks are pretty old), but based on a yield strength of 32,260 psi for A36, I think I'm OK. I was able to calculate the max deformation as about .25" which is allowable based on a length/360 of .33". I think I calculated the maximum stress in the plates (combined) as -2,417 psi, but to be honest, I don't remember how to relate this information to allowable lbs per linear foot on the beam system. I think I'm close, if my calculations were correct, but I can't remember how to close the loop. Any help is appreciated as I've already ordered the steel plates. -Rick
|
| Post Reply Tell a Friend (must be logged in) Alert Admin About Post |
View All | | Next | |
| Replies to this message |
| Re: Residential Beam Load Question | |||
| Re: Residential Beam Load Question -- malagodi | Post Reply | Top of thread | Forum |
Posted by: must be crazy ®  03/31/2007, 15:56:17 Author Profile eMail author Edit |
Can you help me? I'm basically doing the same thing as you. My question is how did you come up with the bolting pattern?
Also, what wouuld be a good screw pattern if i wasn't going to drill all the way through ? |
| Post Reply Tell a Friend (must be logged in) Alert Admin About Post |
Where am I? Original Top of thread |
| Re: Residential Beam Load Question | |||
| Re: Residential Beam Load Question -- malagodi | Post Reply | Top of thread | Forum |
| Posted by: swearingen ® 01/13/2006, 08:27:37 Author Profile eMail author Edit |
Your deflection calc is right if only considering the steel. The wood will help and this number should be less. Be sure you do all of your work and fully tighten all of your bolts very well before removing the column. It will help more to shore up the 5' spans on either side of the lolly column first as well. Assuming the steel is the only thing stressed, the stress would be 19.3 ksi, which is high but within the allowable limits of the grade you have available. |
| Post Reply Tell a Friend (must be logged in) Alert Admin About Post |
Where am I? Original Top of thread | | | |
| Re: Residential Beam Load Question | |||
| Re: Re: Residential Beam Load Question -- swearingen | Post Reply | Top of thread | Forum |
| Posted by: malagodi ® 01/13/2006, 09:17:27 Author Profile eMail author Edit |
Thanks for the post, I really appreciate it. After struggling with the equations for a while, I'm curious. How did you arrive at the 19,300 psi stress figure? Thanks again for help with statics 101. |
| Post Reply Tell a Friend (must be logged in) Alert Admin About Post |
Where am I? Original Top of thread | | | |
| Re: Residential Beam Load Question | |||
| Re: Re: Residential Beam Load Question -- malagodi | Post Reply | Top of thread | Forum |
| Posted by: malagodi ® 01/13/2006, 16:12:47 Author Profile eMail author Edit |
sorry, I figured out my error. I made a mistake on the distance to the neutral axis which, when corrected, yielded a stress of 19,320 psi which you mentioned. Thanks. Is this the result I should compare against the published yield strength? For A36 I found a table that indicated a yield strength of 36,260 psi - I couldn't find a published strength for A36/A50 duel grade. Thanks again for your insight.
|
| Post Reply Tell a Friend (must be logged in) Alert Admin About Post |
Where am I? Original Top of thread | | | |
| Re: Residential Beam Load Question | |||
| Re: Re: Residential Beam Load Question -- malagodi | Post Reply | Top of thread | Forum |
| Posted by: swearingen ® 01/15/2006, 08:41:22 Author Profile eMail author Edit |
Yes, the stress found is the one you compare to yield. Normally in structural applications, the allowable yield stress on a 36ksi beam is 60% of that, or 21.6ksi. Since you're at 19.3, that's why I said it was a fairly high stress. However, since you're using dual grade steel, the actual yield stress is 50ksi, so you are well within strength limits. Remember that this does not affect deflection resistance, so your deflection number is the same. |
| Post Reply Tell a Friend (must be logged in) Alert Admin About Post |
Where am I? Original Top of thread | | | |
| Re: Residential Beam Load Question | |||
| Re: Re: Residential Beam Load Question -- swearingen | Post Reply | Top of thread | Forum |
| Posted by: malagodi ® 01/19/2006, 09:06:58 Author Profile eMail author Edit |
Thanks for your help - much appreciated! |
| Post Reply Tell a Friend (must be logged in) Alert Admin About Post |
Where am I? Original Top of thread |
Powered by Engineers Edge
© Copyright 2000 - 2024, by Engineers Edge, LLC All rights reserved. Disclaimer
