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Joined 1 year ago
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Cake day: June 29th, 2023

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  • I’m an engineer. I use all of it. I use it whether I’m writing technically correct and accurate forensic reviews or doing math in my head (or on paper) to analyze a condition in real time or checking a complex finite element model to ensure that there are no improper assumptions or invalid boundary conditions. AI/ML is really useful for some things, and deadly for others.

    Rote memorization may seem unnecessary, but a mental catalog - whether it be quotes, body parts and systems, equations of natural phenomena, or even manufactured parts and specifications - is the hallmark of someone who can work independently in a real time industry. It may not matter for some jobs, but it’s make or break in others.



  • Yet. Infrastructure on this scale moves slowly and the transparentness of pricing changes on short time lines in physical stores is hard to track. It exists in emergency economies - we call it price gouging - but that’s usually quite obvious. The idea of dynamic pricing has existed forever - hotels, airline flights, movie tickets, taxi rides, even electric rates. As technology advances it offers the opportunity to use the technology to shorten the time window for pricing changes more and more. An extra two tenths of a percent profit seems like a trivial amount. Amazon and Walmart combined for more than a trillion dollars in sales last year. 0.2% is a very non-trivial $2 Billion. If it becomes available, it will be exploited.











  • One option would be to make the beam a flush condition. To get a 16’ span with rafters you’re going to be using at least 2x8s. That’s 7.25" deep. If you were set the top of the beam at the top of the rafters and hang them from the beam (simpson or USP hangers) that buys you some space. Now an 11.88" LVL would only stick down 5-5/8" below the bottom of the rafters. (okay, 5-3/4"-6" with the additional slope over the 5.25" of beam) I’m not saying that a 3 ply 11x88 LVL with a 2.1E, bearing in a BC6 cap on 6x6s would work for your application, but the height tolerance would seem to add up in your favor.


  • The advantage of LVLs are that

    1. you can put them up 1 ply at a time
    2. they hold nails/cut easily
    3. the lumber yard will likely size them for you if you ask

    The disadvantage is that the depth will be about 1/16th of the span when using 2-3 plies.

    The advantage of steel is that an I beam (W shape is what you want, for “Wide Flange Beam”) will be about 2/3 the depth of an LVL. The disadvantages are

    1. An engineer will likely charge you about $600-800 to size this beam, but will also tell you how to top connect it
    2. It will be one piece (fwiw it will weigh about the same as the LVL)
    3. You will have to buy a 40’ piece, or pay a premium to have it cut down from a 40’ piece. (stock lengths of steel are 20’/40’)

    Note that nobody can properly answer your question from the data given (edit - just notice you mentioned 16’ rafters below). You would need to include the span of the rafters and (at least) your location to determine the snow loads and wind loads (edit: and seismic, though it’s unlikely to control for this design) for sizing the connections.

    Disclaimer: I’m a structural engineer, but I’m not your structural engineer. For a long span like this I recommend contacting someone licensed in your jurisdiction to help you out.


  • To take a contrarian view, the plastics wins handily in the reduce scenario. The plastic required to make a bottle is somewhere around 1/25 of the material required compared to glass. It’s high tensile strength and fracture toughness means a huge reduction in material processed per container.

    The flip side to that is convenience - the ability carry and dispose of a 1/2 ounce plastic container, vs a pound of glass container - makes it ideal for conditions where you are less likely to recycle.