huangyhg

replacing wood beam with a steel i-beam
what size of i-beam will i need to replace a wood beam. i have a cabin with a 24' x 24' floor area. the sub floor has 2x12's on two foot centers, which are 12' long, joined at the middle with a slight overlap. these 2x12's rest on a 4x6 wood beam with three 4x4 downposts spaced along the beam. i plan on making this area under the floor a useable basement space without the downposts. they will be in the way for the pool table. my plan is to use a steel i-beam to span the area. in the living area up above this floor there are no bearing walls. i have calculated the weight of the 2x12's and plywood flooring to be 70 lbs. of weight at each spot where the 2x12's will contact the i-beam. this adds up to 770 lbs. of weight on the i-beam, then add furniture and body weight, i'll say a max. load of 1000 lbs. on the i-beam. i'm hopeing a 8" i-beam will work out.
thanks,
mark
find a job or post a job opening
no no
the loading is determined b using the approriate design loads. the residential loading is typically 40 psf ll and 15 dl. the total load is varios combinations, but lets say dl + ll =55 psf (no load bearing walls in the interior). the tributary area of the center beam is 12 ft. so the beam loading is ~660 plf. the deflection limit usual is l/360.
using these parameters you can use a w12x30. but you must design for the 8.3 k reaction at the ends
b001,,
using your 660#/ft your 12"x30# works only if it has ""full lateral side support "". if he can"t support it fully then a 12"x40# works fine with a "actual"deflection of .58" ..with a allowable def. of .800"..
if you need the 8" height criteria, you can use a 8"x58#
but none of this will work without addressing and designing proper end supports!!!!!!
please see your local structural engineer, you need to get this design finished with proper end supports and or new footings. hope this gets you in the ball park.
ray pe
sorry to be unhelpul but..... hire a pe
ray72, don't the 2x12 @ 2' oc provide lateral support? i indicated the supports were required by giving the end reaction.

thanks to you for responding about my i-beam question. i had two seperate structual engineers in town here crunch my numbers and the w8x58 is the final answer. of course with proper footings for the end loadings. this is a great site and i am very impressed with the help!
thanks, mark
always happy to see that you go in the right direction.
ray
i'd like to see how you plan on getting a 24 foot beam weighing almost 1400 pounds in to your basement.
be careful using steel in a residential building.
in a fire the steel will heat up and lose its strength. it was this loss of strength in a fire that caused the collapse of the world trade centre. the facility survived the aircraft impact and only when the steel lost strength enough to buckle did the collapse occur.
steel in a residential fire may not lose enough strength to collapse but when the fire fighters get there they will spray water on everything. this will cause a sudden contraction of the beam and it may warp and buckle. i have seen residential steel beams twisted like a pretzel after a fire. the twisting of the beam can cause as much damage as the fire.
fire protection is essential and i would suggest that you check with your insurance company to see what effect this has on coverage and rates.
at almost 戮 of a ton this is not a do it your self project. the 58 in the w8x58 are the pounds per foot. i would suggest that you price this out first, including delivery.
how are you going to support the house when the existing beam is being removed before the steel one is in place?
you could also look into adding additional wooden beams, parallel to the existing one and perpendicular to the joists, thus breaking the joist span into four spans. you should be able to design a built up beam that will span the 24鈥?if the joist load is short enough.
under the canadian building code, table a-8 forming part of clause 9.23.4.32(3) a 5 ply 38x286 (2x12) will span 7.03 m or (23 鈥? with a 2.4m (8鈥? supported joist length if you use douglas fir select structural grade. to go outside this range you would need an engineers design but i would think that a 6-ply beam would work.
you could also use an engineered wood product or wood truss. this could be a do it yourself project and not weigh as much. the existing beam could stay in place until the new supports are in place.
rick kitson mba p.eng
construction project management
from conception to completion
rdk, the man wanted ... "i'm hoping a 8" i-beam will work out"
all of your post is a nice reference, but the 8" height requirement for the design is what's needed, we can always do it at 12". as far as the fire situation goes, do you really think that a 24' square, one story bungalow building will generate enough heat to last until all the combustion material is exhausted and then bend the beam? i imagine, that after the fire, the house will supply enough charcoal to roast the 600# pig using the new 8x58 steel beam. lol
boo1
""ray72, don't the 2x12 @ 2' oc provide lateral support? i indicated the supports were required by giving the end reaction.""
the new end reaction loading only holds the beam up. the existing overlapping joists just sitting on the new clear span do not laterally support the steel beam. joist attachments must be spec'ed out by his engineer depending on his solution.
pylko
""i'd like to see how you plan on getting a 24 foot beam weighing almost 1400 pounds in to your basement.""

any engineer, with experience in the field, can see that his clients can complete his designs.
ray72
when i have installed steel i beams, we fastened a 2x on top then nailed the joist or rafters to the 2x. i have never seen joist or rafters laying (un-attached) to a beam. so....

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