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Everything posted by Purdueenginerd

  1. Anytime a building is constructed, the structural engineer needs to design the foundation. The foundation design is based off of the soil conditions at the site. The geotechnical engineer consultant will bore down in several locations at the project site and provide important information for the design team. For the structural engineer, depending on the project, the geotechnical engineer will provide test data with actual values for the structural engineer to use. For example: for a spread footing design, the geotechnical engineer will provide an "Allowable" bearing pressure at a given depth. Why does this matter? Without it, a structural engineer is forced to design the foundation based off of prescriptive minimums denoted in the code. As you might imagine, those values are not good. For the owner, getting soil sampling can reduce construction costs and make the building more durable. The geotechnical engineer also provides recommendations to the civil engineer! For example, if the building has a slab-on-grade, but the top soils have a high-plasticity and are susceptible to movement and swelling, the geotechnical engineer might recommend removing 4-8 feet of the top soil and replacing it with select fill! You'd actually be quite surprised. I have a project right now where I'm designing four 1 story buildings all within about 200' of eachother. The geotechnical report took 8 samples. There's a limestone gravel layer with a nice allowable bearing pressure of 30,000 PSF (thats a fanastic value). The depth of that layer is 5' in one spot and 30' in another. So one building has drilled piers 35' and another building, its only 10'. In an area like Houston, with a lot of alluvial deposits soil conditions below grade can and do change drastically. Buffalo bayou has not had a static location for the majority of its existence and proto-streams and different conditions likely flowed through downtown Houston eons before even humans were on the north american continent. Now you may ask, what are normal values and was is PSF? PSF stands for Pounds per Square foot, and I'm simplifying things here a bit but there are two main directions loads or energy get transmitted into the foundation, Laterally (ie, wind an seismic), and Vertically (Gravity, Dead, Live, and overturning from wind and seismic). When a building a designed, the structural engineer will size the foundation element based on the values provided by the Geotechnical engineer. Lets say he/she gave me a value of 4000 PSF at 8 feet down (which is more or less normal for Houston). Lets say I'm just designing a spread footing. A spread footing, for lack of a better terminology is a block of concrete, typically directly beneath a column or vertical member. Most of the time they are square, but technically can be any geometry. (ive had several petro-chemical projects with octagonal spread footings). Anyway, lets picture a 5'x5' (looking down, in plan) spread footing. Thats 25 square feet. I would expect that to carry 100,000 lbs load (vertical only). (25 *4000 psf = 100,000 lbs). Not bad right? Now lets picture if the owner elected not to get soil sampling done and I had a column with 100,000 lbs of force. How big would my spread footing need to be? 100,000 lbs/1000psf = 100 square feet. Or 10'x10'. It would also have to be thicker for other reasons I'm not going to touch on right now. Now, imagine a building with 50 columns, those cost savings will add up quick!
  2. Crane has some nice christmas lights on the main support member. Nice little touch driving home from work on Friday.
  3. Yeah, Houston contractors are really bad about sidewalk closures. Normally poorly thought out compared to other cities. Not sure if this is handled at the permitting office or not.
  4. Keep in mind that some affordable housing developments are merely that because they set aside a certain number of units for lower income residents, instead of concentrating poverty into one large tower. I pretty much categorically oppose your proposal that the poor should be relegated to trash land, like junkyards and concrete plants. Land, even in midtown, is relatively cheap and is a good spot for middle, lower, and upper classes to co-mingle and go to work together. As for the costs associate with building a high rise. Yes its typically more expensive than a low rise building, BUT, it uses less land to create the same number of units, which also has costs associated with it.
  5. more common than you think! Even for small-ish pours. Refer to section 2.4 http://dl.mycivil.ir/dozanani/ACI/ACI 305R-99 Hot Weather Concreting_MyCivil.ir.pdf (older version)
  6. Concrete curing procedures are based on ACI 308.1 (http://dl.mycivil.ir/dozanani/ACI/ACI 308.1-98 Standard Specification for Curing Concrete_MyCivil.ir.pdf) (link is for the 1998 version, I think the latest version is actually 13). Can't tell what they've put down from the photos but at least from 200' away they appear to be complying with section 2. A contractor, should follow curing procedures on all of their concrete placements. Outdoor Flat work pours are especially susceptible to damage if procedure isnt followed. The reason for performing these actions is because when concrete cures, the chemical reaction of water and cementitious materials puts off heat, ie, it is an exothermic reaction. A temperature differential between the interior and the exterior faces of the concrete can built up tensile stresses and cause large cracking in the face of the concrete (this is bad!) In addition, for flatwork and/or outside pours, air flow, evaporation, and sunlight can change the strength characteristics of exposed sections of the concrete(this is bad!). Curing procedures are put in place to make sure these bad things dont happen or are mitigated. IE, ensuring that exothermic concrete can dissipate heat more quickly, or alternatively, make the concrete uniformly warm. For Mass pours.. or concrete placements that are huge. Additional steps have to be taken to mitigate these affects. ACI207.1R-14 (http://dl.mycivil.ir/dozanani/ACI/ACI 207.1R-05 Guide to Mass Concrete_MyCivil.ir.pdf) (i've provided an older version). Provides guidelines and specifications on how to handle that. The history section of the commentary is quite educational if you'd like to learn more. There are additional specifications for Hot weather and Cold Weather concreting.
  7. yeah, lots of earth work on this one. Agree with you Triton. Very large project for 358 units.
  8. A few years ago I had a repair project at petrochemical facility where we had a mass-pour with a high-early strength concrete. A 2' thick concrete roof deck for a below grade structure. After the concrete set (to give you context on how fast it was setting, I could walk on one side of the roof while the other side I would sink into), the contractor basically flooded the top of the concrete with 3 inches of water. The next morning, I recorded the water temperature at 120ºF. It was stunning to me how much energy it put out curing. The contractor indicated they had a fire break out several years back because of extreme exotherming of the setting concrete.
  9. agreed. thats an awesome photo. The volume capacity of a concrete truck is about 10 cubic yards fully loaded. I'm counting about 25-28 trucks total lined up. Thats a lot of concrete.
  10. The entire building is about 10k sq feet.
  11. I know a few actually who do. I do collect old AISC steel construction manuals (though I use them for work still on occasion) Right now I have 1st, 5th, 6th, 7th, 8th, 9th, 13th, 14th, 15th edition. My 1st edition is dated January 1930. Found it for about 60 dollars online. The 5th, 6th, 7th, 8th, 9th I have found at Half-Price Books over the years, each for about 15-20 dollars. 13-15 Ive used in my professional career so I bought them when they were/are still active codes.
  12. Yes! You want the concrete and rebar to act as a composite material. The rebar deformation patterns were standardized in 1947. Before then there was a lot of variance on rebar deformation patterns and a lot of proprietary shaping by manufacturers . Even older concrete structures (Normally pre-1920's) have "smooth" bar.
  13. its 13 pounds per linear foot. Excellent paper weight material!
  14. Fun Fact! #3 bar, Diameter 3/8" #4 bar, Diameter 4/8" #5 Bar, Diameter 5/8" #6 Bar, Diameter 6/8" #7 Bar, Diameter 7/8" #8 Bar, Diameter 8/8" #9 Bar, Diameter 9/8" (also 1 in^2 in cross area) - Pre 1940's, #9 bars would traditionally be square 1"x1" bars. #10 Bar, Diameter 1.27" (They stopped using the previous numerical system) #11 bar, Diameter 1.41" #14 bar, Diameter, 1.693" #18 bar, Diameter 2.257" Here's a picture of #18 bar I took the other day
  15. This comes off as a little needlessly accusatory, FYI. Anyway, to settle the population density of Houston here's an interactive map, from 2014. https://www.arcgis.com/home/webmap/viewer.html?webmap=85a821d13a4f4502a85f71c4aae8bae8
  16. I would consider midtown houston to be part of the city center. I know when I lived there I routinely used the light-rail to get to downtown and the med center. I would imagine a not-unsubstantial percentage of midtown residents commute to either downtown or the med center and contribute to the pedestrian traffic of both. If theres going to be signficant residential growth in the city center, Midtown and South Downtown are primed for the most growth, in my opinion.
  17. Indeed, a lot of the themes are covered in the book, with the exception of the tunnel system: though I'm not sure I agree with the author in regards to his opinion regarding the tunnel system.
  18. Been to a few job sites where I have to do this. I think its a good idea. Stretching and flexing is certainly cheaper than an OSHA recordable from pulling a muscle. I like it.
  19. Tried going down that way with my wife a few weeks ago. Got frustrated with all the construction around the med district and cut back through midtown...
  20. I tried looking up some more updated press on this one. https://setexasrecord.com/stories/513240744-construction-worker-alleges-negligence-caused-fall-through-floor-at-holiday-inn-site Only thing new this indicates is that this confirms they were in the middle of a concrete placement when the collapse occurred.
  21. Thought i'd share this book. I burned through it on one flight from Houston to Chicago last weekend without falling asleep. https://www.amazon.com/gp/product/0865477728?pf_rd_p=183f5289-9dc0-416f-942e-e8f213ef368b&pf_rd_r=ZVY9XHD60ZJT1W7AJ7RB Nonetheless, little dated, but Houston is mentioned a few times, in a negative light. There's some good data points on pedestrian infrastructure and policies to create more walkable neighborhoods. I found the book rather compelling.
  22. I might be subject to recency bias in my opinion of the typical projects Gensler peforms, at least from my anecdotal standpoint. I'm not trying to convey theyre snobby, I apologize-- that wasnt my intent. I guess every time I've worked with Gensler its typically a huge multi-national firm as the owner. Hopefully thats not enough to doxx me ; ). That's why i'm generally surprised they would go for and win the bid for a parking garage, even one that's automated. My only thought would be that something else is attached to this project that hasnt been revealed yet. Alternatively, perhaps Gensler just has a lot of experience with this automated garages in other markets and thats why they won.
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