Astra Tower

Astra Tower is a 450 foot tall residential building made of reinforced concrete. It will surpass the Wells Fargo Center as the tallest building in Utah. Jacobsen Construction should have the building complete by the end of 2024.

This post is my best photos up until now. I'll make more posts as the building progresses.

Astra tower as of June 20, 2023. The tower consists of a reinforced concrete core, concrete columns and shear walls, and post-tensioned concrete floor slabs. The large shear wall on the left is the north wall. It is full of steel embeds - steel plates embedded in the concrete to which future facade panels will be welded. I kinda like the exposed concrete, though.

The site on August 6, 2021. A Carl's Jr. restaurant was demolished to make way for the building. On the left you can see some preliminary excavations to expose the footings of the adjacent building to the north. That is an old brick pawn shop which will soon be dwarfed by Astra.
I'm very lucky there is a large parking structure right next to the site. It's a great vantage point.

Foundation work begins! This is my favorite part of a construction project. I don't know what it is about reinforced concrete, but it just fascinates me.
The blue machine with the large black boom is a rig for drilling the deep foundation piles. Rebar cages are lined up along the bottom of the photo (West end of site), along with ~100-foot-long hollow threaded pipes which will also go into the piles. Along the North perimeter (left), a short shoring wall has gone up to protect the pawn shop. 4-5 feet of soil has been excavated along the North side to flatten the site for drilling.

Pile installation continues. This photo gives a better look at the 130-foot-tall drill rig. It's basically a large hollow auger. After drilling to depth, as the drill is retracted, a cement slurry is pumped down through the hollow auger into the hole. Once the drill is removed and hole is full of slurry, one of the thick (3" diameter I would guess) threaded steel pipes is inserted in the hole. Then, a cylindrical rebar cage is inserted. Once the cement cures, the pile is complete.
At the center of this photo, you can see excavation around some of the completed piles. These will tie into the foundation.

Bad day. Here is the large drilling rig on its side. It tipped late the night before while they were moving it to drill another pile. The two cars visible were severely damaged. The owner of the silver car came out of a show at a nearby theater to see their car destroyed. The only injury was the drill operator who fell 12 feet or so, fracturing his back. All things considered, it's amazing more damage wasn't done. If it fell a bit more to the North, those old brick businesses could be leveled.

Surveillance video taken from the rear of the pawn show shows the rig fall.
Rig Collapse Video
The report of the accident reveals several equipment procedures were not being followed when the collapse occurred. Work at the site is paused for a number of days.
Visiting the site after the rig was removed, I noticed it had smashed a large electrical transformer box as flat as a pancake.
A replacement drill rig showed up a week or so after the accident to finish pile work.

At the Northeast corner of the site, the tops of the piles are exposed. There are no below ground levels in this building. 6 levels of above-ground parking structure will be topped with residences.
Rebar for the foundation will be tied into the pile reinforcement, and one massive foundation will result.
The thickness of the footing here is 7 or 8 feet. Further South (upper left) where the core of the building will rest, the foundation grows to a thickness of about 20 feet.

Lots going on in this photo. Pile installation is complete.
The pile tops from the previous photo are at the far left. A pad of concrete has been placed to facilitate level rebar placement. Just to the right of those piles is 8-4" power conduits. These will be encased in the concrete foundation.
The upper center of the photo shows footing rebar assembly has started. An amazing jungle of rebar ties into the piles. Dead center in the photo (just up and left of the yellow mini excavator) is where the base for the tower crane will be incorporated into the footing.
Excavation for spot footings is complete at bottom left. Each spot footing rests on several deep piles. Excavation continues along the West side (bottom of photo).
At the top of the photo on the sidewalk is a group of finely-dressed business people. Not sure who they were, but they were very interested in the site as one man pointed things out to them. Perhaps they are stakeholders in the building.

Another view of the Northeast corner. The concrete slab has been placed and reinforcement for the foundation is starting to go down. Formwork is going up at the right side of the photo. The adjacent worker helps show the scale of the thickness of this foundation. The power conduits are seen running along the center of the photo.

Tons and tons of rebar get placed and tied. Waterproofing membrane (white) begins to line the walls of the excavation.
A large white drain line has shown up near the Southeast corner. This may be the main sewer line for the entire building, but I'm not sure.

Spot footings are formed and rebar installed. More drain lines snake through the foundation. The final shape of the main foundation is becoming more clear.

Long reach!

Green collars are added to each of the central threaded bars in each pile. I assume these are to act against uplift of the foundation, but I could be wrong.

Nearly ready for concrete. The base for the tower crane is in place (red truss structure at the center). Column reinforcement sticks up from the foundation rebar. 

Two pumps ran all day to place all the concrete in the main foundation. Smaller spot footings were poured earlier. I made sure to write my initials on some pennies and toss them in there a few days before this, now they'll be buried in concrete forever.

Core rebar. I guess there is a little bit of room left for concrete.
The parking garage in the background is where I get my aerial shots. Security doesn't like me loitering there.

Columns begin to rise. A bit to the right of center is a large footing for one of the shear walls which will rise the entire height of the building.
The tower crane is now assembled and in use.

Steady progress.
The first deck forms are going up along the North end. These first 6 floors will be mainly parking garage. I believe part of the Southeast corner will be residences starting at level 2.

First post-tensioned decks are poured. The parking garage ramp slopes down to the South.

The tower crane. I think this is a called luffing boom crane. The counterweight assembly is coupled to the boom and dynamically moves in and out to balance the load. One crane is all that will fit on this small site.

Another setback: Formwork collapsed during a concrete pour for the first parking garage slab. After this happened, much more diagonal bracing was added to these tall red formwork posts.

An aerial view of the formwork failure (just above the center of the photo). The red strands crisscrossing the deck are post-tensioning cables. Some of these cables are seen hanging where the formwork failed beneath. No injuries resulted to my knowledge.
All the concrete seen in this photo had to be saw cut and removed before trying again.

After the concrete mishap, vertical progress accelerates and hasn't stopped. During the day, the site is buzzing, but all is quiet in the evenings when I visit.
The concrete core keeps ahead of the decks by only 2 or 3 floors. At 95 State, one block North of Astra, the core was nearly at its full height when steel began to rise.
I have a lot of respect for those organizing projects like these. It can't be easy.

A side view of the deck slabs and formwork. Small black dots along the slab's sides mark each post-tension cable. After each cable is tensioned, the excess is cut off, and the hole filled with grout.
Similar concrete structures often use deep concrete beams to support the decks, but this building has no such beams. Keeping the decks so thin means more floors and higher profitability for the owner.

Dozens of tension cables run along the slabs and through columns.

The top of the parking structure makes a great spot for material staging and rebar cage assembly. Precast concrete cladding is hung from the floor slabs, and windows follow.

95 State

95 State is a 25-story, 515,000 SF office tower built in Salt Lake City from 2019-21 by Okland Construction. It was designed by Skidmore, Owings & Merrill.

The foundation work on this building was fascinating. It was my first opportunity to experience the scale of a high-rise building's enormous foundation.
First, excavation takes the site down to about 30 feet below street level. You can see the shoring lining the site-large timbers span vertical steel beams which are tied back into the retained soil.
Once excavation is complete, piles are placed in the earth. I'm not exactly what kind of piles these are, but I'm assuming they are reinforced grout friction piles. A giant machine drills a deep 24-inch diameter hole into the earth, which is immediately filled with a cement slurry-basically concrete without the rock and gravel aggregate. Then, a cylindrical rebar cage is inserted in the slurry. Once the concrete hardens, 11 feet of the soil between the piles is excavated and the hardened slurry removed, exposing the top portion of reinforcing steel in the pile. The pile is then incorporated in the forms and reinforcing steel for the footings of the building. You can see the tops of these piles in the photo-small circles scattered throughout the rebar.
363 of these piles are drilled 110-115 feet deep down into a layer of dense gravel which can support the weight of the building above.

Rebar for the massive 11-foot-thick footings is assembled and formed up. Notice on the left side of the image-triangular shaped footings called "grade beam outriggers". I believe these are designed to transfer loads from the perimeter building columns into the stronger central core of the foundation. The cap of a pile is visible at bottom-center.
Space on a downtown job site is hard to come by, so construction materials are stored wherever there's space.

Concrete for the footings is poured. Vertical rebar clusters are the beginnings of vertical concrete columns. Horizontal rebar shows where grade beams with connect more footings together. The base of the building's concrete core is visible at the left, and formwork for the core is being assembled.
This building has 1 basement floor of below-ground parking on this south end and 2 levels on the north end which is all reinforced concrete. The rest of the building is a reinforced concrete core with steel structure and concrete floor deck with a glass curtain wall facade.

The concrete core-home to elevators, mechanical chases, and stairways, begins to rise. An intricate system of reinforcement assures the strength and durability of the 392-foot-tall structure.
The tower being located in a dense urban area means I can have great views of the construction. Pedestrian access remains constant around the site, so I can see all the work up close.

The core continues to rise. After a section is poured, the formwork is released and is jacked up one floor level. Rebar is assembled, concrete poured, and the process repeats.

Here we see embedded steel plates in the core. Additional steel connector plates will be welded to these-creating a place for the steel structure to attach to the concrete core.

The core continues to rise, followed by steel erection.

Photo from Loopnet
The finished tower. The first two levels above the lobby are a meetinghouse for the Church of Jesus Christ of Latter-Day Saints.

I learned a lot from this article in Structure Magazine.

First post - Salt Lake Temple

 I take a lot of construction photographs. Until now, I've posted many of them on Instagram, but I wanted a place to post more photos and document what I'm seeing.

This first post will be about the Salt Lake Temple. I'll just post the highlights of the hundreds of photos I've taken during the project. The temple is currently being renovated and seismically retrofitted using base isolation. I visit the temple often, and look forward to documenting my observations here.

Base isolators staged west of the temple. Each one weighs 18,000 lbs. 98 of these will completely support the 187 million pound temple.

Base isolators staged west of the temple. Each one weighs 18,000 lbs. 98 of these will completely support the 187 million pound temple.

Excavation exposes the original foundation. Holes are drilled into the stone, through which steel rods are placed and bolts tightened on each side-compressing and tying together the foundation.

New steel roof trusses. Extensive steel reinforcement is being added throughout the temple to strengthen the existing masonry. I believe these new trusses will run alongside the old steel trusses which were added in a previous renovation. I have heard that all new steel connections made in the temple itself will be bolted instead of welded wherever possible to prevent fire in the historic structure.

New steel roof trusses. Extensive steel reinforcement is being added throughout the temple to strengthen the existing masonry. I believe these new trusses will run alongside the old steel trusses which were added in a previous renovation.

I have heard that all new steel connections made in the temple itself will be bolted instead of welded wherever possible to prevent fire in the historic structure.

Steel pipes are placed side by side beneath and perpendicular to each wall of the temple. These pipes are hydraulically jacked beneath the temple with the soil being removed by hand. This process is called "Jack and Bore". Once the pipe is in place, grout is pumped between the outside of the pipe and the surrounding soil. A rebar cage and sleeves for tensioning cables are inserted, and concrete follows.
The temple will sit on these beams, which transfer the load to the seismic base isolators.

Just right of center in this photo is where a portion of the foundation of the temple has been completely removed. There are 8 or so steel beams running beneath and supporting the masonry wall above. You can see them marked with roman numerals. These beams are hanging off of a large steel beam on each side of and running parallel to the wall. These two larger steel beams rest on new concrete foundations.
The east and west walls of the temple have the new steel/concrete beams running their entire north/south length. These gaps in the foundation allow for the interior end of those beams to be exposed and tied into the new foundation. There are four such gaps in the foundation. You can see the inner end of one of the steel/concrete beams in the gap shown here.

Rebar cage and sleeves for tensioning cables are inserted into the steel pipes prior to concrete. The sleeves are difficult to see in this photo, but the 4 sleeve ends are visible in the plywood cap.

Larger 7-foot steel pipes are inserted beneath each exterior stairway of the temple. I'm not sure the reason behind this. Intricate rebar cages and cable sleeves are placed in each prior to high strength concrete.

The excavation adjacent to the temple is complete, and work begins on the new base isolator foundations. The rebar cage being assembled is the footing where the base isolators will rest. Construction workers placing rebar help with the scale of the photo.
Original ground level of the temple is located at the bottom of the stone stairs near the top center of the photo.

The rebar cage for the base isolator footing nears completion on the west side. Footings similar to this run along each side of all the exterior walls of the temple. Again, workers inside the rebar cage show the scale. These footings are just shy of 6 feet thick.

Steel reinforcement of the corner tower masonry. I think because these are soon to be installed, much of the towers are now filled with reinforcing steel.

Northwest of the temple, work on the grounds progresses. The new building at the left will house restrooms.

Atop the large base isolator footings, more precise concrete pads are prepared. Templates for the base isolators assure that this concrete is placed perfectly.

Piles of reinforcing steel are continually delivered to staging yards west of Temple Square.
During a school trip to Schuff Steel in Lindon, I saw some fabrication of some of these pieces. Our guide told us that each piece is unique due to the the nature of the masonry construction of the temple. Detailed measurements and precision fabrication is required to make sure each piece of structural steel will snugly fit alongside the historic masonry.

The first base isolator is placed on May 3rd, 2023. A video with members of the construction team is being made. Barely visible on the right edge of the base isolator is a small shiny scale model of the isolator, used to demonstrate the technology in the video.

Notice what look like pipes sticking out of the large concrete footing beneath the base isolator. These angle down and in toward the temple wall. I believe these are more sleeves for future tension cables.
The square red steel plates bolted to each side of the base isolator stabilize it during construction. I imagine removing these plates will be one of the final steps in this massive project.

Isolator installation ramps up.

At the top of the south wall (left side of this photo) is shown a white boom. This is a precision rig for drilling holes down through the entire wall to the foundation. Through these holes will run steel rods or cables which will tie the new roof structure to the foundation, compressing and strengthening the tall masonry walls.

The foundation is removed above the larger steel pipes beams. I'm not sure if it's cut all the way through to the interior or not. Interestingly, much of the steel pipe to the left of the larger pipe is exposed. You can see the layer of grout which was pumped between the pipe and the surrounding soil after they were jacked into place beneath the temple.
The massive concrete beams which top the isolators and tie into the ends of the steel pipe beams begins to take shape. Rebar is welded directly to thick steel fins which are welded directly to the tops of the pipes.

Great view from the Conference Center. The 3 or 4 levels of new construction north of the temple is reaching final grade. The renovation of the Church Office Building/Main Street Plaza continues.

There is an unbelievable amount of work happening on this project. I'm lucky to live so close and to be able to keep up with it. I love seeing advanced construction and engineering techniques used to preserve such historic structures.

    I think future posts won't cover such a large time span. Ideally, soon after I take some photos I'll just make a new post. Maybe that means that each post will be short, but I think it will mean I can go into more detail. We'll see how it goes.