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Post by Gokhan on Jun 18, 2013 9:19:22 GMT -8
I keep wondering what the lifespan of the grids is and what happens when they become iron oxide. I am guessing definitely a lot more than the lifespan of the line. They wouldn't use corrosion-prone steel for those wire meshes. Probably something not as expensive as stainless steel but more expensive than regular rebar steel.
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Post by darrell on Jun 18, 2013 9:21:06 GMT -8
I keep wondering what the lifespan of the grids is and what happens when they become iron oxide. Are they that different from the rebar used to reinforce concrete? Cured concrete is permiable to water, and the strength of a reinforced concrete bridge depends a lot on all that rebar. Is there some ultimate lifespan, after which the bridge is at risk of collapse, or is the steel rebar stable after some surface rusting? Here are two sections from the Wikipedia article on reinforced concrete:
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Post by Gokhan on Jun 18, 2013 9:31:33 GMT -8
Are they that different from the rebar used to reinforce concrete? They are obviously a lot different per your pictures. They are shiny-silver-colored -- probably zinc-plated steel or some other corrosion-resistant steel. As joemagruder must have tried to point, they will get a lot more wet inside the backfill material than rebars in concrete.
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Post by Gokhan on Jun 18, 2013 12:12:12 GMT -8
Formwork is progressing on the Venice Bridge. Note the arch shape near the supports. The falsework over the median can't be built until Monday or so when the last support will be unwrapped.
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Post by darrell on Jun 18, 2013 17:23:19 GMT -8
Formwork is progressing on the Venice Bridge. Note the arch shape near the supports. That's peculiar: I see the curve, but don't see how an arch works with this skewed bridge of single-track bridges. The crossings of Washington and National on the other side of the arched Culver City station aren't arched.
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Post by Gokhan on Jun 18, 2013 19:29:50 GMT -8
Formwork is progressing on the Venice Bridge. Note the arch shape near the supports. That's peculiar: I see the curve, but don't see how an arch works with this skewed bridge of single-track bridges. The crossings of Washington and National on the other side of the arched Culver City station aren't arched. However, the supports in Phase 1 are arched. Perhaps they are making up for straight supports in Phase 2.
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Post by Alexis Kasperavičius on Jun 19, 2013 7:14:35 GMT -8
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Post by culvercitylocke on Jun 19, 2013 8:32:36 GMT -8
Coverings and form came off of the final Venice Bent last night.
And last week, in preparation for Venice blvd street reconstruction they cut down several trees on the venice median east of National, as well as trees on the north side of Venice blvd.
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Post by Gokhan on Jun 19, 2013 11:45:32 GMT -8
Coverings and form came off of the final Venice Bent last night. Yes, I saw it, too, and it's good news. They still need to do backfill at its base. The falsework construction over Venice Blvd median could start soon once that done.
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Post by culvercitylocke on Jun 19, 2013 13:42:14 GMT -8
Also from Dwights new pictures comes the news that they were pouring the bridge/station for Sepulveda yesterday.
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Post by bzcat on Jun 19, 2013 16:18:27 GMT -8
Also from Dwights new pictures comes the news that they were pouring the bridge/station for Sepulveda yesterday. I saw them pouring concrete in a weird place (not in the direct line of sight of the bridge). After viewing Dwight's photos, I see that they were pouring concrete for the LADOT parking garage
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f ron
Full Member
Posts: 222
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Post by f ron on Jun 19, 2013 18:12:19 GMT -8
There are rebars sticking out of the ground on the ROW between Overland and Westwood. Looks like the beginning of sound wall construction. I thought there was just a fence here and no wall? There's no soundwall on that side of the tracks but it's possible that the rebar --which is adjacent to the sub-station may be the beginings of a retaing wall structure. This is the last of the Northvale trench stretch to get something to hold up the track bed. It's been installed everywhere else there already. That said the rebar is also adjacent to some grating. Hard to imagine they'll be laying the bed over it but then maybe they will. Which comes first by the way? The sound wall or the track bedding? Attachments:
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Post by Alexis Kasperavičius on Jun 19, 2013 19:10:26 GMT -8
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Post by darrell on Jun 19, 2013 20:30:08 GMT -8
There are rebars sticking out of the ground on the ROW between Overland and Westwood. Looks like the beginning of sound wall construction. I thought there was just a fence here and no wall? There's no soundwall on that side of the tracks but it's possible that the rebar --which is adjacent to the sub-station may be the beginings of a retaing wall structure. This is the last of the Northvale trench stretch to get something to hold up the track bed. It's been installed everywhere else there already. That said the rebar is also adjacent to some grating. Hard to imagine they'll be laying the bed over it but then maybe they will. Which comes first by the way? The sound wall or the track bedding? Dwight replied, "That is for a retaining wall between row and tpss" He also wanted to pass on:
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Post by Gokhan on Jun 19, 2013 22:14:01 GMT -8
Tonight they will construct some of the falsework over the eastbound lanes of Venice Blvd. It will take about three weeks to finish it and then another three weeks to finish the falsework over the westbound lanes.
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Post by Gokhan on Jun 19, 2013 22:23:46 GMT -8
There are rebars sticking out of the ground on the ROW between Overland and Westwood. Looks like the beginning of sound wall construction. I thought there was just a fence here and no wall? There's no soundwall on that side of the tracks but it's possible that the rebar --which is adjacent to the sub-station may be the beginings of a retaing wall structure. This is the last of the Northvale trench stretch to get something to hold up the track bed. It's been installed everywhere else there already. That said the rebar is also adjacent to some grating. Hard to imagine they'll be laying the bed over it but then maybe they will. Which comes first by the way? The sound wall or the track bedding? It's a ballast-retaining wall. Apparently it's somewhat stronger and possibly higher than a regular ballast-retaining wall in order to protect the TPSS agans damage in a possible derailment. There may also be a visual barrier on top of it so that Overland Elementary kids in the classrooms can't get distracted by the trains. There is a sound wall on the other side. Sound-wall foundations also serve as ballast-retaining walls and therefore no ballast-retaining wall on that side is necessary. Once these walls are finished, they will grade the right-of-way, lay subbalast (fine gravel) and a weed-retardant cloth and then the ballast (coarse gravel). They will place the ties and then the welded track on them. They will cover the ties with ballast and bring a special train to align the tracks and settle the ballast. The very last process is to grind the tracks with a rail-grinder train. Once the sound-wall foundations and frames are done, sound walls can be placed at anytime. Once the sound walls are placed, the next process is for you to start sleeping in peace. They will also coat them with anti-graffiti glazing at some point.
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Post by culvercitylocke on Jun 20, 2013 10:03:42 GMT -8
What are stems and sofits?
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Post by Alexis Kasperavičius on Jun 20, 2013 10:33:55 GMT -8
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Post by joshuanickel on Jun 20, 2013 10:43:39 GMT -8
What are stems and sofits? Here is a diagram to help describe it:
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Post by Gokhan on Jun 20, 2013 11:34:03 GMT -8
Nice, informative picture!
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Post by Gokhan on Jun 20, 2013 11:56:24 GMT -8
Nothing at Venice Blvd yet. They are behind schedule for some reason. Some forms came off at Palms Station: Not sure why they were scraping off concrete on these forms. I hope it didn't come off because the forms were removed too quickly: You can see that they are breaking off the concrete at the edge of the new abutment to expose rebars so that they could build the inner retaining wall, which will also house some utility rooms: The same is being done at the old Motor Ave abutments to enlarge them. A lot of DWP utility relocation is taking place throughout Palms. They will also cut a trench across National to connect the TPSS to the DWP box.
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Post by rajacobs on Jun 20, 2013 13:23:30 GMT -8
Gokhan noted that "Some forms came off at Palms Station..." And this afternoon, the walls were being covered with black plastic. I'm imagining this is to deter graffiti "artists."
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Post by Gokhan on Jun 20, 2013 13:27:02 GMT -8
Gokhan noted that "Some forms came off at Palms Station..." And this afternoon, the walls were being covered with black plastic. I'm imagining this is to deter graffiti "artists." Both for protecting concrete during curing and, yes, from the taggers in the long run. They will also be glazed with an antigraffiti coat later.
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Post by Gokhan on Jun 20, 2013 14:20:24 GMT -8
Not sure why they were scraping off concrete on these forms. I hope it didn't come off because the forms were removed too quickly: expolinefan verified that the forms were removed too early (in a day?) and the concrete was still adhered on the forms and the concrete wall came off along with the forms as a result.
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Post by roadtrainer on Jun 20, 2013 19:07:21 GMT -8
|Years ago I was working on a job where we were pouring concrete into wooden forms, before any form got cement we would give it a good coat of oil.Thereby when the cement cured we were able to remove the forms with no problems, perhaps somebody forgot to put some oil on the forms or none at all.
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Post by Gokhan on Jun 21, 2013 11:14:19 GMT -8
I saw more of this today. It appears that they are testing the forms -- not really a form-removal failure:
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Post by Gokhan on Jun 21, 2013 11:15:37 GMT -8
Some falsework went up over the westbound support in the Venice Blvd median last night:
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Post by Gokhan on Jun 24, 2013 12:24:48 GMT -8
Motor Avenue abutment widening is taking place. The abutment is being widened on the north side (freeway side). You can see that the old abutment had a step structure. Not sure if it had any cast-in-drilled-hole (CIDH) foundation but the widened portion will have. They also exposed some rebars of the old abutment. You can also see that they are casting some wall on the top portion of the old abutment -- possibly an emergency side walkway. East abutment, north side: East abutment, looking toward north: The wall they are building on top of the east abutment, south side: Looking southeast toward the east abutment: West abutment, north side, drilling for the CIDH pile: West abutment: South side of the west abutment: Looking east on National Blvd just west of Motor Ave, nothing like the mother nature's spontaneous landscaping, somehow finding a way to flourish through the crack between the sidewalk and curb -- beautiful: Venice Bridge falsework, looking southwest:
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Post by darrell on Jun 24, 2013 13:51:14 GMT -8
Motor Avenue abutment widening is taking place. ... Love the detail, thanks, Gokhan!
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Post by Gokhan on Jun 24, 2013 21:34:22 GMT -8
I was surprised that there is no corrosion whatsoever on the year-1963 -- 50-year-old -- rebar.
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