SAN FRANCISCO | Park Tower at Transbay | 605 FT | 43 FLOORS

[SoCal Alan]

It's Sunday, and I'm procrastinating on my taxes , so here goes:

IMHO, it seems pretty inefficient to do concrete and rebar for the first so many (11?) floors. They have to remove (and reapply) the outer forms each time (instead of self-rising). Is it a cost issue (concrete/rebar vs steel)?

I would think that steel is easier, because of the precise measurements done beforehand, whereas concrete/rebar involve a lot of repetitive exact placement of forms and measurement/laser/alignment. Not to mention placement all of the temporary support underneath the floor forms (on top of poured concrete).

Also, what is the relative difference in strength/stability of concrete/rebar vs steel? Isn't steel more stable when undergoing a latitudal (is that a word ) movement in let's say an earthquake motion?

[viewguysf]

I don't have it at my fingertips, but remember reading they wanted to have very large floorplates at the bottom to appeal to tech companies.

[Jerry of San Fran]

SoCalAllan - from what I have read concrete has been formulated to be very strong today. And the rebar adds it's own qualities to the mix. I was surprised when I saw a building being built with reinforced concrete in San Francisco & started to ask questions as we live in an earthquake zone. You can see an interesting article comparing the two here: http://precast.org/2013/09/steel-concrete-yin-yang/

[Pedestrian]

Originally Posted by SoCal Alan

It's Sunday, and I'm procrastinating on my taxes , so here goes:

I did my taxes a week ago and sent them certified/return receipt so I can track them. Still sitting in the Fresno Post Office undelivered. I read they had floods in Fresno. Wonder what's going on.

what is the relative difference in strength/stability of concrete/rebar vs steel? Isn't steel more stable when undergoing a latitudal (is that a word ) movement in let's say an earthquake motion?

From what I've always read, it's more a question of rigidity than strength. Reinforced concrete tends to be the medium of choice for residential because people don't tolerate even the slightest sway in strong winds or small quakes in their homes--can bust the crockery. Steel can and is oftened designed to move and absorb such forces. As we have seen in buildings like the new hospital on Van Ness, there are even dampers that can be incorporated into the framework to absorb even more such forces: http://www.cwejournal.org/vol10nospl...an-earthquake/

Reinforced concrete, because it is more rigid, has to absorb the energy of wind pressure or a quake through sheer strength although there are also clever ways to minimize unavoidable motion in certain designs like the liquid damping system (essentially a giant water tank with internal baffles) atop One Rincon Hill.

Anyway, a rigid podium/flexible tower design, while unusual, seems like it could have advantages. Among the main ones in this case seems to be less weight than an all-concrete structure (meaning a less robust foundation required). In a sense, they seem to have transferred some of the performance requirements of a robust foundation above ground to the podium.

[iamfishhead]

Story three is coming along nicely

2017-04-17 11.26.55 by Joshua Goldstein, on Flickr

[Pedestrian]

Originally Posted by Jerry of San Fran

SoCalAllan - from what I have read concrete has been formulated to be very strong today. And the rebar adds it's own qualities to the mix. I was surprised when I saw a building being built with reinforced concrete in San Francisco & started to ask questions as we live in an earthquake zone. You can see an interesting article comparing the two here: http://precast.org/2013/09/steel-concrete-yin-yang/

Back in 1989 there was much discussion of this issue in relation to the failure of the Cypress Structure and other elevated freeways which were, of course, reinforced concrete. The concrete may have been improved--a lot of that has to do with the "mix" or the relative proportions of cement and gravel (and you see building failures often in the developing world because builders "cheat" by using too much gravel and too little cement)--but the discussion back then centered on the rebar. The difference in the amount and configuration of rebar in new code-compliant structures vs what was used when Bay Area freeways were built in the 1950s and 1960s is amazing. For one thing vertical columns now always have dense vertical rebar clusters held together with circumferential loops of more rebar. It almost looks like the finished structures are about 50% steel although that's probably an exaggeration.

[pseudolus]

Another pour today. Prior pour was April 12. The floor before was in two stages March 17 and 22, so they're picking up the pace.

[iamfishhead]

A picture as of today

2017-04-25 11.32.25 by Joshua Goldstein, on Flickr

[timbad]

from ground level, Saturday

[iamfishhead]

Look's like there'll be another pour real soon!

2017-05-04 16.01.29-1 by Joshua Goldstein, on Flickr

[Pedestrian]

^^If by "real soon" you mean today:


https://app.oxblue.com/open/clarkconstruction/parktower

[pseudolus]

Originally Posted by pseudolus

Another pour today. Prior pour was April 12. The floor before was in two stages March 17 and 22, so they're picking up the pace.

And April 21 and now May 5, for those keeping score.

[Pedestrian]

^^But this was floor 4. Didn't somebody say only the bottom 7 were going to be poured concrete? If so, then 3 (plus the roof of the pdiuum section) to go before we switch to steel.

But by this rendering, it looks to me like the podium is 8 floors (and a roof). That would be 5 more pours of this size and then I assume the tower would be steel.

[iamfishhead]

Originally Posted by Pedestrian

^^But this was floor 4. Didn't somebody say only the bottom 7 were going to be poured concrete? If so, then 3 (plus the roof of the pdiuum section) to go before we switch to steel.

But by this rendering, it looks to me like the podium is 8 floors (and a roof). That would be 5 more pours of this size and then I assume the tower would be steel.

I thought it was 10-12 floors

[fimiak]

Not the most interesting photo, but it is a night shot, so its at least unique.

[iamfishhead]

Here's the completed fourth floor and the start of the fifth

2017-05-08 10.38.49 by Joshua Goldstein, on Flickr

[Pedestrian]

This afternoon:


By me

[pseudolus]

It appears that little or no progress has occurred since a week ago.

[timbad]

[iamfishhead]

I think the next pour will start soon

2017-05-23 11.54.10 by Joshua Goldstein, on Flickr