Purdueenginerd

^  Interesting info, Purdueenginerd.   Thanks.  If I read your post and the referenced materials correctly, installing something like TopGolf on the GRB roof would require the roof to be raised to a load level roughly 5 times as strong as the current roof, and building parking on the roof (which has been considered and found to be infeasible) would only require twice the load strength of the current roof (presuming the building was not over-engineered).

 

FWIW, I believe the GRB roof is actually approximately 11 acres, with the north and south additions.

Maybe. The truth is., We dont know what live load the roof was originally designed for. What we do know, is that 100 psf is a minimum design live load for a 'roof garden'. But using the assumption that baseline live load calculation was 20 psf back when it was originally built. Then the live load would increase by a factor of five. Using the term live load is important, because the total load would not increase by a factor of 5. The designer still has to account for rain, snow, self weight, wind, etc... Total load, might only increase by 1.2 or 1.5:

Now, in-feasibility is a tricky term in regards to design and engineering. I would opine that from an engineering standpoint, it would be doable to put parking on top and even top golf. The controlling factor is probably like many things: Cost & Benefit. 

Note: no factors of safety, reduction factors etc accounted for. 

Doesn't matter to me what they build on the roof of the GRB, but that's ~8 acres of prime real estate that should have something be it solar panels, Top Golf, soccer fields, park, helicopter landing pads, parking spaces, apartments, train station, botanical gardens, or whatever other ideas they can come up with.

To add to the conversation at hand:

Minimum Uniformly distributed live loads Table 4-1 ASCE 7: Minmum Design loads for buildings and other structures

Top Golf, Soccer Fields, Park, Botanical Gardens

Roof used for roof gardens: 100 psf

Helicopter Landing Pads

Helipads: 60psf (for helicopter with max take-off weight of 3000 lbs or less)

Parking Spaces

Garages with Passenger vehicles only: 40 psf

Train Station

For the trains: a lot-- I'd have to look at another code, but train supports would be very heavy

for the passengers waiting for trains the classifcation would be Assembly platform: 100 psf

Apartments

New structural editions, but floor loading is normally 40-100psf for apartment buildings. Depending purpose of room and portion of floor. 

So, I dont understand the anger going on here. I personally think top golf would be a great idea. But, as a structural engineer let me chime in on roof loading. In houston, roof loads have to account for downward, and uplift windloads. Snow loads, ice loads,  rain loads, self weight/dead load. 

For live load uniform distribution, the roof with no utilization aside from, being a roof will have a live load of 20 PSF (ASCE7 Table 4-1), or Pounds per square foot: So a 100x100 foot roof, is designed for 200,000 lbs (ballpark), of live load IN ADDITION TO its self weight, windloads, snow loads, ice loads, rain loads, etc...

Now, lets imagine they put "top golf" on top. That changes the classification to "Roof used for roof gardens" (table 4-1). And the LIVE load to 100 PSF. That means to the roof (100x100ft) would be designed to hold 1,000,000 lbs of live load IN ADDITION to the aforementioned.

And for the record, parking garage live loading is specified at 40 PSF(ASCE 7 table 4-1. People throwing around 7 million lbs: Thats not a lot of load. Cars, are relatively speaking: Pretty light. 

 

Finally, the equipment "air conditions, etc" is accounted for (likely) within the dead load calculation. I would guess, that that roof design already has a capacity between 100-250 psf.

:Edit: I see the area is 8 acres, or 348480 SQ Ft.

Therefore, a roof garden would be 34,848,000 extra lbs of live load. Sounds like a lot... but not impossible. To give you an idea of how strong these structures are in compression. One 12''x12'' concrete column (@4000 psi) can hold 576,000 lbs (Ballpark) in compression before it explodes (literally) (assuming buckling doesnt control). Would it require strengthing? Maybe/probably. Is it difficult? Not really. Is it expensive? Yes.

/Note, all loads unfactored. No factors of safety. No accounting for moments, etc... 

Not bad. Modern with a little flair. 

That drill looks like it is for geotech tiebacks for retaining walls. Hard to tell from that distance though. 

Youtube video explaining typical procedures

Sheesh. Commercial and residential construction workers safety culture is stunning to me sometimes...

Plasma torching without a faceshield. Shortsleeves. 

Saw cutting without a respirator

Improperly wearing a fall arrest harness. 

Fascinating. It already has the look of a dorm. I guess the students would take the lightrail to campus. 

Call me a skeptic though. Rice is a pretty wealthy school. I'd imagine they'd build some really nice dorms if needed. 

Thats awesome. You can see how the sign protected the paint behind it from UV bleaching. Guess it used to be a bright red.

http://swamplot.com/whats-getting-thrown-out-the-window-at-the-abandoned-days-inn-downtown/2014-09-03/

Swamplot noticed some of the changes going on. 

thanks for sharing. Welcome to the board

haha. Yeah. Its a finishing tool for larger placements. Power Trowel is the more 'official' name, but I like zamboni just as much. 

This is probably one of the most documented concrete pours in Houston history...

 

Looking at the webcam, it seems as though they are covering up the concrete with plywood or dirt...can't really tell since the webcam images aren't as nice as all of yours. 

Thats burlap and Plastic.

Helps cure it better and regulates temperature at the top so the sun doesnt bake it as much. 

Good question,

I dont know. haha. They look kind of like grade beams. Not too sure though. 

Great shots, I know some of you guys liked my comments over on 609 main (hines) about foundation construction and concrete consolidation. You can see one of the Vibrators (donkey dicks) laid out next to the crane base in the 2nd photo. 

Good action shots. 

Saw a few comments on population density for houston. I took a bit of time to gather some information in a handy spreadsheet. 

Source:  http://projects.nytimes.com/census/2010/map

Houston, TX. I isolated populations affected by the light rail within the 610 loop + the Galleria/uptown area. This includes pretty much the entire west side, Eado, moody park area, 3rd ward, rice area... etc.

I might add the rest of the inner loop another day...

https://docs.google.com/spreadsheets/d/1Yb0ikorR9cz-iIdfLkwNHbv8uWP4319VpG_5UgFA2XM/edit?usp=sharing

Population density of 5362 person/sq mi, in the subject areas puts us on equal footing in regards to population density as inner city houston, pre-1940 when trolleys were the predominant form of mass transit in the city. Re-Urbanization, in the last decade for Houston, especially on the west side where the majority of light rail lines are proposed, is well underway. 

/edit, looks like the built in spreadsheets dont work: Try the google docs link I made. 

I'm not going to get into the debate regarding rail (i happen to be pro-rail)...

But designing a BRT, so that it can not be upgraded to Light Rail (one that already exists in this city), has got to be one of the silliest things I've heard. Sharper 90º degree turns? Are these politicians that fearful of efficient design that theyre going to mandate a sharper 90º turn? What next - 10 percent grades every once and a while to throw off those pesky trains??

Thats pretty ridiculous. 

haha Dont know if any licensing boards are going to continuing education credits with the name "Purdueenginerd" signed at the top as credible

That's very interesting thanks for the insight PurdueEngineer. If I may ask, what kind of engineer are you? Structural or Civil?

And one more question, those piles that surround the shaft, are those similar to piles that go deep into the soil or do they not provide and large load bearing support at all?

Structural and Forensic Engineering are about 70 percent of my work day. Civil and Mechanical (not very advanced mechanical) are probably the other 30 percent. 

I don't do much 'new construction'. Most is fixing things that are failing/failed.

The perimeter piles are probably utilized as retaining structure. Designed to resist the lateral load of the soil below the street surface and provide a safe working environment for the crews working below grade. For load bearing, in regards to the building-- I doubt they'll be utilized for that purpose---at this interval. But we'll know within a few weeks. Those piles can go pretty deep. But how deep?  Say the hole in the ground is 20'. That means, it has to resist 20' deep of lateral soil pressure. The pile will try to rotate when the lateral soil pressure presses on it, what prevent its from rotating?--- More soil below the hole. So... those things probably go another 35-40 feet below the street. I'm simplifying the calculation massively as there's a lot more to take into account, but conceptually that is essentially their purpose. 

Great question Grizz,

So to answer this question, I'm going ask you to imagine you have just squeezed a pile of ketchup on your plate. That pile is maybe 1'' high. Even though Ketchup could be classified as liquid, why doesnt it  spread out like say water, or oil would on your plate. There is property of liquids called "viscosity". The property deals with internal stresses between the molecules that can be summed as Viscosity is quantified measure of resistance to internal stress. Water flows, because its internal stresses are not strong enough to overcome the force due to gravity. Ketchup internal stresses, can sort of beat out gravity.  Say you want to spread the ketchup out without touching it. Youre going to pick up your plate, and vigorously vibrate the plate (not violently). As you apply that vibration, you are adding more internal stresses to the pile.  What happens? Your ketchup pile spreads out. 

http://en.wikipedia.org/wiki/Viscosity

Now concrete, is a little similar (though not as delicious). ASTM, ACI standards generally indicate that concrete shouldnt be dropped from a pump hose end for over 4'-6'. The crews are <likely> going to take the pump hose to the bottom of their reinforcement. Concrete will be pumped there and form a pile. ACI and ASTM standards will then dictate that they have to vibrate it. We often use a concrete vibrators, dubbed nicely by crews as a "donkey dicks". (http://www.harborfreight.com/power-tools/concrete-vibrators.html). This spreads out your concrete and helps consolidate the material around the reinforcement. At THAT point, its just a matter of keep pumping, and keep "filling up" your form. 

The next issue comes on the engineering side. There are very accurate scientific tests, performed to determine a viscosity of the a liquid. In construction, I dont care for that accuracy. A test is often performed in the field called a slump test(http://en.wikipedia.org/wiki/Slump_test). The drop in concrete after the test is performed is a method used to 'sort of' determine how workable or flowable the concrete is. A highway might use a 1'' slump, thats very low. If the engineer specified a 1'' slump for say, this pour... the crew would mutiny and murder him. So the engineer knows the mix design he needs and will specify a slump based on that. 6'' slump is pretty workable. Mix design/slump can be altered with a chemical additives such as plasticizers (http://en.wikipedia.org/wiki/Plasticizer) and superplasticizers. Aggragate selection and water content also can alter material properties. 

Finally there's another option. If rebar density is SO dense, that proper vibration is difficult or impossible. The engineer might specify whats called a self consolidating concrete (SCC). THis concrete is so liquid-y that its slump  could be considered 10''-11''.  The beauty of those concretes are that its material properties allow for the suspension of the coarse aggregate during placement--- IE... the rocks won't sink! If they select that concrete, at that point its just a matter of 'filling up' the tub. 

 

All Soil moves over time. Geology is not my specialty. Soil Sublimation can be a problem in this area because of oil extraction and water extraction, which changes soil characteristics. Clay, sand, etc will move, if a load is applied. As an engineer, other than rapid seismic loads, I can't account for the geology of this area. The only load I can design for is, the loads from the building into the soil. I have to calculate weather the soils will move, if I apply a load to it. If the answer is no- then my design is sufficient. If an unknown underground river 600 feet below the building, collapses thus moving all the clay above it--- "Well, shit that sucks" is going to be my response.

But soil acting like a wave, thus slowly moving. Yeah- that makes sense. But none of the buildings in downtown houston are design to last throughout the geological era of this region. 

Thats a tough question. 

Maybe. So, Chase tower is taller, and I think has a smaller foot print than 609 Main. Which means two problems. Higher pressure on the soil due to less area & and more windloads due to taller height. Its hard to speculate, but maybe they dug down 60 feet, instead of 30 feet to achieve their footing. Maybe they drove piles & built a large footing. I think chase tower is also a steel frame, which makes it could make it lighter than a reinforced concrete structure of similar height. 

So look, Burj Khalifa, Tallest building in the world had a footing, but also had a shit ton of piles that went a whopping 160 feet down. Their soil conditions are sandy- which performs worse than clay. (Link below for UAE soil maps). My most recent geotech design project, I designed a foundation 30 feet from the ship channel-- Soil samples hit 3000 psi--- within 5 feet depth (and totally saturated in water). No soil condition is the same, but clay soils arent as bad as many think. 

https://www.uaesis.ae/imf/imf.jsp?site=ADSIS&u=everyone&p=everyone&Submit=Submit

So on a building like this, I always thought there were piers that went down deep into the ground, from which the building frame was constructed. With this giant slab, it looks like they're essentially building the building on top of a giant concrete raft floating on the clay 30 feet below ground. Can you explain it?

Piles arent needed if you the bearing and uplift pressures in the soils can be achieved within the depth they dug down. Piles would still need a transfer slab/foundation at the top of the piles to distribute loads to each pile. I didnt see if they installed piles on this project. but lets assume that foundation doesnt have piles and that the footing they poured is 300 ft by 150 ft and their soil tests showed that the bearing pressure is 4000 PSI. Off the cuff, calc without any adjustment factors shows that the soil will support 2,160,000,000 lbs- before it starts to move. Reinforced Concrete is 150 lbs per cubic foot.  Which means I could pour 300 ft x 150 ft x 320 foot (tall) Solid Block of reinforced concrete before the soil could fail in bearing, just from its weight-- and as you know buildings are mostly hollow. Now, thats just vertical weight. I doubt it controls. Wind loads and overturning moment are probably the controlling factor regarding geotech design. 

Someone mentioned piles arent used because bedrock is too deep. Thats not entirely true. Bedrock is, in fact, probably too deep. but really think about this. Say the Geo tech testing determined that at 40 feet deep, the soil pressure capacity is 4000 psi. But at 80 feet deep. Its only 5000 psi. How many piles (with their small cross sectional area) driven to 80 feet do I need to reach the same capacity has a gigantic footing at 40 feet? Where his/her degree of truth comes in, is that if bedrock was at 40 ft depth and had a pressure capacity of 13000 psi. In which case yeah, piles might be worth it. 

Basically, like many things it depends. I actually, would have assumed some piles would have been installed: but it all depends on the geotech conditions. No geotech site in Houston is the same. 

Disclaimer: Armchair engineering & and most of my foundation design is substantially smaller than this. 

This is for sure the foundation slab for the high rise. Parking garage loads are puny compared to the skyscrapers. 

 

Hope we get some good photos of the pour... Thats a massive one. My biggest concrete pour is 500 cubic yards. This looks like 15,000. 

Only 1000 off. Darn!

yeah, Im not sure what purpose they serve. I see C-Channels, oriented along the weak axis, cantilevered in the wrong spot to the beam. I think Phillip might be right, though I'm not too sure myself. I think to add to his comment, you can see studs welded into the C-Channels. Looks like nelson studs... but I cant tell.