huangyhg

weight bearing loads for steel beams
i manage a scrap yard and sell steel beams (typically 8w x 21lb. x 30ft. long) customers are always asking me how much weight can this hold? i cannot answer them. is there a chart or some way to figure this out? for example if one is adding a second storey to an existing structure, and they have dimensions of the area to be added, they ask how much can this beam hold and/or how many beams would they need to span this area. i usually tell them to check with their architect or an engineer. i would like to be able to answer them here if possible. anyone have any answers?
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you are giving the correct answer. any other answer would open you up to liabilities you do not need to be exposed to. don't even attempt to answer that question yourself.
the craft is in the aisc, steel construction manual, table allowable moment in beams.
26 ft unbraced length allowable total moment is 13.5 kip
the design process for a steel beam can be summarised as follows:
a) determination of all forces and moments on critical
section
b) selection of ub or uc
c) classification of section
d) check shear strength; if unsatisfactory return to (b)
e) check bending capacity; if unsatisfactory return to (b)
f) check deflection; if unsatisfactory return to (b)
g) check web bearing and buckling at supports or
concentrated load; if unsatisfactory provide
web stiffener
h) check lateral torsional buckling; if unsatisfactory
return to (b) or provide lateral restraints
i) summarise results
trying to be a good citizen and offering some help to them could be construed as the practice of engineering. if you are not licensed to practice, then the best move is to refer them to a structural engineer as you have been doing. regulations vary from one area to another and so do local building codes.
i want to commend you on telling them to go and consult with an engineer. the w8x21 can carry various loads depending on the application, amount of load, location of load, whether it is a uniform load or concentrated load, is it dynamic load (i.e. vibrations, fatigue considerations). it also depends on the span length and is the span simple or continuous over several supports and what types of supports. how often is it laterally braced. is the load concentric or is it eccentric, any torsional effects, the boundary conditions for the ends are they fixed, pinned, free, does it has a cantilever. last but not least, what grade steel is it (astm a-36, astm a-572 grade 50 or the newest steel astm a-992)
as you can see due to all of the above and much more, engineers on this forum can not say how much a w8x21 or any other beam can carry.
the awareness on structural components is important rather advise on
i want to jump on the bandwagon and also tell you that you are giving the correct answer. aside from structural capacity, there is another thing we need to consider is deflection. i don’t know who you sell the beams to, but if it is a homeowner deflection is a major concern. most people really don’t want a bunch of cracks in the plaster or tile of their house.
dear mr. sro,
thank you for your addition

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