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Purdueenginerd

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Purdueenginerd last won the day on April 1 2015

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About Purdueenginerd

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    I work as a Structural engineer in the construction industry. I specialize in structural engineering for remodeling, renovation, and repair projects. Work for Architects, contractors, and owners. Highrises, midrises, university, hospital, residential, commercial, industrial and heavy petrochemical; I'm all over the place. My hobbies are Cycling, Traveling, reading, PS4 video games, and food; I also enjoy large construction developments, viewing construction project progress, architecture, and urban planning... which is probably why I'm on this website.

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  1. @hindesky Those are post tension or prestress ports. There are three times of structural concrete construction 1. Traditional Reinforced concrete 2. Post Tension Concrete 3. Pre-stress concrete To understand the three, a brief cursory explainer on how structural concrete works. Concrete is very weak in tension, Great in compression! Lets talk about No. 1 first. In traditional concrete, lets imagine a simple concrete beam with no reinforcement (ie, rebar). Concrete, like every material on this planet, will bend. If you imagine a sagging beam, the bottom of the beam will be in tension, and the top of the beam will be in compression. With no rebar, the concrete will crack at the bottom and quick propagate upwards, splitting the beam in half and causing collapse. Ever see a martial artist break concrete block in half? This is exactly what is going on. Theyre impact is "flexing" the block, creating tension on the bottom face and subsequently breaking the block. In traditional reinforced concrete, rebar is added to the bottom of the beam to engage and resist those tensile forces. Above is the cross section of a typical reinforced concrete beam design. I wont go into the equations too much, but you'll see that the top of the beam is in compression, the bottom of the beam is in tension (as denoted by C and T, respectively). Now what are the limitations for this? In traditional concrete construction, the tension zone effectively always exists, this limits how long the span is. In addition the more load you have on it, the "deeper" the beam required to create a sufficiently large concrete compression zone. For parking garages, is generally desirable to have long spans between columns because that means: more parking! So what is post tension? When the concrete is cast, they create this holes all the way through the beam/girder all the way to the other end. While the structure is shored, they'll run these high strength cables through the beam and tie them at both ends. The cables are then tightened, aka, tensioned, and locked in place. The tension in the cables in effect "compresses" the concrete. Remember concrete is great in compression. Post tension effectively put more of the concrete section into compression. Advantages include the ability to go longer spans with less depth. Disadvantages: less modifiable and more expensive to build-- Can also be dangerous if a cable fails. To answer your question, those holes are for post tension cables. Pre-stress is very similar in principle. You will most often see pre-stress concete in pre-cast garages. Prestress means that the cable was tensioned before the concrete was cast, then they poured the concrete and subsequently released the cables from tension, (which then applied a compression force on to the concrete. These are common at plant manufactured concrete shapes, that are trucked to the job site and put in place at the construction site. The disadvantages are similar to post tension. As for why theyre working on an already existing garage: Not sure. unless it was to make repairs or modifications. associated with the builing that may go up next door. This garage looks like a pre-stress/precast garage.
  2. Dont believe this is applicable to this forum. I have fond memories of ashville though, good hiking.
  3. I have a tiny repair project at a hotel. They are Howling about price for the repairs and trying to equivocate whether the repairs are needed. I imagine this is related.
  4. My specialty isnt bridges, but it is important to note that the code that governs the structural engineering of bridges (AASHTO) is generally more stringent than the code(s) that cover buildings. The statement in the news article is alarming but sort of vague. A brief explainer on load combinations. In both the building code and bridge codes, the predominant system of design today is Load Resistant factored design. (In Wood, Masonry, Soils and some steel structures - the old system is still used sometimes,). Long Story short, the engineers classify different types of loads. I'll just use 3 for example, but there are a lot more. Dead Load(DL) - Self weight of the building/structure Live Load(LL)- typically a transient load/mobile load ie, people. Wind load(W)- Pretty self explanatory. The engineer takes those loads and applies factors to them. Then puts them in different combinations! For example, in the building code here are 4 combinations that you'll likely see. 1.4 * D = Factored Load 1 1.2 *D +1.6L = Factored load 2 1.2*D+1.0W+0.5L =factored load 3 0.9*D+1.0W = factored load 4 Then for each member in a building, the engineer will compare all the load combinations with the capacity. I'm only showing you 4 load combinations, but the structures I work on, its not unrealistic to have 20 to 30. Accounting for wind directions, uplift etc. This system results in "more efficiently" designed structures. A brief example fictitious example: I have two buildings that weigh 2000 lbs: 1 building has to hold up a 1000 lb statue. The 2nd building has to hold up a dance floor with for 1000 lbs of people. Building 1, per code, would have to be designed for 1.4*(3000lbs) = 4200lbs Building 2, per code, would have to be designed for 1.2*2000lbs +1.6(1000lbs) =4000 lbs The reason i'm goign through this giant explanation is that the bridge code, has even more load combinations. Including load combinations on specific lanes loaded, and other lanes unloaded. They got load combos that include vehicle braking force, thermal force, wind, seismic, ice, rain, snow, the list goes on. What this sounds like to me: They missed a load combo. Does it mean it will fail? Not necessarily. It sounds like theres a potential for damage during a load imbalance. Which may get remedied by restricting the amount of lanes in the south bound span until the other span is complete. This is the more concerning to me. The soils part is a bit alarming, because I would presume a pretty substantial geotechnical report was performed for this test. I would imagine they have cut into a bit of their factor of safety for one of the load combinations. Without knowing what exactly is wrong regarding the stability, I cant imagine a full demolition and start over is cheaper than trying to make modifications to the existing structure. I could see it being done out of an abundance of caution, mostly because things went south very badly with the FIU bridge. Anyway, apologies for the wall of text.
  5. Anecdotal, but I have one renovation project in San Antonio so far has been put on hold. For my projects that are under construction, most of the contractors are implementing cleaning regimes, spreading out the workers, and then one project of mine split their workforce into 3rds and put them on day shift, evening shift and night shift.
  6. Yeah, the sign price I actually think sounds about normal for what I would expect fom IAH and HOU Signs. My smirk is more of a, "why spend a million dollars of tax-payer dollars on a sign". I'm being a bit of a debbie downer on this one, sorry.
  7. To be clear, I dont think many architects view those styles with "contempt" and in my opinion its mistaken to state that. The reason "classical" buildings arent built anymore is because thats what owners fundamentally demand. Picking specifically on offices. Many owners and tenants wanted offices with a floor to ceiling windows, maximizing natural light. What does that mean: Glass Curtain walls! As for making buildings look older, generally I see this at the University level. Buildings on campus will typically have architectural guidelines. Many Larger universities employ a university architect to make sure whatever building is being constructed will comply with the standards. I actually do not know how new construction federal buildings deal with architecture, I do know there are building code differences from the structural side of things. Historically, I have worked on two very old (former) federal buildings, both of which are by this guy: https://en.wikipedia.org/wiki/James_Knox_Taylor - I particularily like that he signed both the Architectural and Structural Drawings for my project (1912) Back in 1900's, he was basically the architecture dude of the Federal Government. There used to be an office that handled Federal Building Architecture: https://en.wikipedia.org/wiki/Office_of_the_Supervising_Architect_for_the_U.S._Treasury I believe it was cut short due to WWII and ongoing tensions with with private architecture firms and accusations of improper bid awards. After the war, I'm sure the anti-communist fever of centralized buildings helped impede its return. My personal opinion, given the presidents ongoing business connections to architecture and construction firms related to his real estate empire, I'm a uncomfortable with the president diving into another industry wherein he stands to benefit financially from. Feel free to call me "elitist", I also find The Presidents 'tastes' to be tacky, at least architecturally speaking. While I do like older style buildings, I think it wouldnt hurt to let each state nominate or appoint an architect to come up with standards for local jurisdictions. Like I said before, federal building standards already exist, I dont think it would be a significant jump to put in appearance standards. Finally, touching on craft/skilled labor. This is anecdotal, but the two buildings I worked on, while they had ornate components: could easily be replicated today. Unrelated, Ive had a few older buildings with decorative Terra-cotta that needed to be replaced and that had to be specialty ordered from one of the few remaining companies that fabricates them. Why isnt terra-cotta used on buildings anymore? Its heavy as hell, more susceptible to weathering and deterioration. Finally, to create ornate elements: Super expensive... Which as far as taxpayer money goes... a lot of people will raise hell about.
  8. Few of my projects outside of Houston have been office --->hotel conversions. Havent seen it too much in Houston yet.
  9. Yep, 1997 should be designed for 40 to 50 psf live load. At 2.3 you'll be good! If you want to confirm, your house is new enough that you should be able to get the drawings from the City of Houston permitting office. Most of the time the live load rating is listed in the general notes.
  10. Depending on the age of the structure, most single family residential homes are designed for a uniform distributed live load of between 40 and 50 lbs per square foot. The deadload is already accounted for in the capacity of the structural members. That being said, at 48x7x10 is an area of about 23 square feet. This comes out to about 2.3 lbs/sq feet. Even if its heavier than carpet, it will marginally eat into the live-load rating capacity of your floor,. Sructurally that likely wouldn't concern me. If you need more assurances or something in writing you'll want to hire a structural engineer. The only thing for is if the space was attic and then converted into occupy-able space. If it used to be attic space, my answer would differ. Best of luck.
  11. They just play U2's "Where the streets have No Name" on a loop the entire time youre there.
  12. agreed, I rented at Post Midtown in 2009, right after the financial crisis. If I remember correctly the 2 bedrooms (I had a roommate) were running like $1300/mo total at the time. That price point rose precipitously as the years went on.
  13. People forget that when Post-Midtown, Camden Midtown , Ventana at Midtown were built, Midtown was sort of a dump. Rents werent particularily expensive (at least compared to now) back in the early 2000's for those places.
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