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The problem with reinforced concrete (2016)

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Re: The problem with reinforced concrete (2016)

#151

Post by mcguire »

mc32 wrote: post #101
mortenjorck wrote: post #98

Earlier quoted context omitted.

People quote this figure often, but it really only applies to detached single-family dwellings, which are commonly built for a single owner. Japan certainly doesn't build larger structures such as office buildings for thirty-year lifespans – no one has floated any plans to tear down the Kasumigaseki Building yet: https://en.wikipedia.org/wiki/Kasumigaseki_Building

Have things changed in the last decade or so[1]? Japanese loathe “second hand” stuff if they can avoid it. This includes property. The service life for buildings is 47 to 50 years or so, for depreciation purposes. Totally unrelated, but I love that 1000 year old wooden temples get rebuilt every 20 years or so[2] because of the religious idea of renewal. [1] https://japanpropertycentral.com/2012/06/what-is-the-lifespa…

Possibly.

"A recent innovation in the Japanese real estate industry to promote home ownership is the creation of a 100-year mortgage term. The home, encumbered by the mortgage, becomes an ancestral property and is passed on from grandparent to grandchild in a multigenerational fashion. We analyze the implications of this innovative practice, contrast it with the conventional 30-year mortgage popular in Western nations and explore its unique benefits and limitations within the Japanese economic and cultural framework." The 100-year Japanese residential mortgage: An examination (1995) (https://www.sciencedirect.com/science/article/abs/pii/106195....)

Re: The problem with reinforced concrete (2016)

#152

Post by LegitShady »

ClumsyPilot wrote: post #149
LegitShady wrote: post #122

Earlier quoted context omitted.

Municipal and other budgets are already highly strained all over. If the cost of an interchange or large culvert goes up 2x to increase its lifespan, you can do less work now. Your level of service goes down now. There are trade offs to everything. Build something much more durable, pay twice as much, do half the work in a season and get more complaints. We already aim to build infrastructure based on estimates of fu…

Budgets are strained precisely because they are saddle with 50 year old structures in need of maintenance. Only a small % of the budget goes to new construction. Saving a little on the upfront cost only to pay a lot more for maintenance is a false economy. Stainless steel rebar does not double the cost of construction, and neither does high quality concrete. We need to stop buying subscribtion to "bridge as a service…

> Budgets are strained precisely because they are saddle with 50 year old structures in need of maintenance. Only a small % of the budget goes to new construction.

You have it exactly backwards - most of the budget goes to capital construction - replacement of existing structures and roads. The maintenance budget is constantly shrunk.

>Stainless steel rebar does not double the cost of construction, and neither does high quality concrete.

Last I checked stainless rebar was ~3x the cost of regular rebar...

"high quality" concrete doesn't mean anything. Most concrete is high quality.

>We need to stop buying subscribtion to "bridge as a service"

All infrastructure requires maintenance and eventual replacement. Bridges will never be permanent and will always require regular inspection, maintenance, etc.

Re: The problem with reinforced concrete (2016)

#153

Post by ClumsyPilot »

rektide wrote: post #47
throwawaysea wrote: post #23

An interesting read, albeit with information that is likely familiar to many. Given the issues surrounding concrete with greenhouse gases, recycling, and landfill contribution, it seems that timber ( https://arstechnica.com/information-technology/2012/05/wood-... ) may actually be a more viable alternative. We have techniques to grow it sustainably, it can be a carbon sink within a city, and it is mostly natural wood…

This is the only post I found mentioning recycling, and I think that's a key factor in this all. My generation is going to be the first saddled with a lot of old buildings we have to deal with. We are going to have to get good at recycling buildings. My understanding that the economics have already really pushed us massively forwards in the past decade or two, that we are far more aggressive about recycling construct…

"I feel like there's a consumer lack of understanding. The invisible hand can't push effectively here"

When I asked the real estate agent what's the expected lifespan of a house, she looked at me like she's just seen an alien. In fact, half the time, they don't even get the floor space right and every floor plan comes with a disclaimer "maybe this is wrong"

Re: The problem with reinforced concrete (2016)

#154

Post by ClumsyPilot »

LegitShady wrote: post #152
ClumsyPilot wrote: post #149

Earlier quoted context omitted.

Budgets are strained precisely because they are saddle with 50 year old structures in need of maintenance. Only a small % of the budget goes to new construction. Saving a little on the upfront cost only to pay a lot more for maintenance is a false economy. Stainless steel rebar does not double the cost of construction, and neither does high quality concrete. We need to stop buying subscribtion to "bridge as a service…

> Budgets are strained precisely because they are saddle with 50 year old structures in need of maintenance. Only a small % of the budget goes to new construction. You have it exactly backwards - most of the budget goes to capital construction - replacement of existing structures and roads. The maintenance budget is constantly shrunk. >Stainless steel rebar does not double the cost of construction, and neither does h…

"Last I checked stainless rebar was ~3x the cost of regular rebar"

But it's 5-10% of the total building cost, and if you bump that to 20% the corrosion goes from "always' to "probably never"

Re: The problem with reinforced concrete (2016)

#156

Post by mc32 »

mcguire wrote: post #151
mc32 wrote: post #101

Earlier quoted context omitted.

Have things changed in the last decade or so[1]? Japanese loathe “second hand” stuff if they can avoid it. This includes property. The service life for buildings is 47 to 50 years or so, for depreciation purposes. Totally unrelated, but I love that 1000 year old wooden temples get rebuilt every 20 years or so[2] because of the religious idea of renewal. [1] https://japanpropertycentral.com/2012/06/what-is-the-lifespa…

Possibly. " A recent innovation in the Japanese real estate industry to promote home ownership is the creation of a 100-year mortgage term. The home, encumbered by the mortgage, becomes an ancestral property and is passed on from grandparent to grandchild in a multigenerational fashion. We analyze the implications of this innovative practice, contrast it with the conventional 30-year mortgage popular in Western natio…

My understanding is the cost is mostly the land and the building not so much. I think Sweden introduced a law limiting mortgages to ~100 years[1] because property prices were becoming unaffordable to many. So this may be more about "affordability" than longevity of buildings, but time will tell.

[1]https://www.thelocal.se/20160324/sweden-limits-mortgage-loan...

Re: The problem with reinforced concrete (2016)

#157

Post by zelon88 »

mrfusion wrote: post #133
wahern wrote: post #29

Earlier quoted context omitted.

> The author states that "one of iron’s unalterable properties is that it rusts" yet further on acknowledges the existence of stainless Even stainless steel rusts, just more slowly. Roughly 10-100x more slowly, judging by https://www.nrc.gov/docs/ML1124/ML112490377.pdf and https://www.mdpi.com/2076-3417/10/23/8705/pdf .

What are car mufflers made of that they resist rust so well?

You must not live in New England.

Re: The problem with reinforced concrete (2016)

#158

Post by LegitShady »

ClumsyPilot wrote: post #154
LegitShady wrote: post #152

Earlier quoted context omitted.

> Budgets are strained precisely because they are saddle with 50 year old structures in need of maintenance. Only a small % of the budget goes to new construction. You have it exactly backwards - most of the budget goes to capital construction - replacement of existing structures and roads. The maintenance budget is constantly shrunk. >Stainless steel rebar does not double the cost of construction, and neither does h…

"Last I checked stainless rebar was ~3x the cost of regular rebar" But it's 5-10% of the total building cost, and if you bump that to 20% the corrosion goes from "always' to "probably never"

if you need to weld the rebar into cages (like you often do) then the cost goes up even more as welding ss is harder.

But you're not wrong in general. There will still be corrosion in the concrete eventually but less likely from rebar oxidation.

Re: The problem with reinforced concrete (2016)

#159

Post by ggcdn »

raylad wrote: post #99
robocat wrote: post #73

Earlier quoted context omitted.

> Does anyone know? Is anyone testing? In first-world countries/states with earthquakes, the answer to this is often yes and yes. A good article from 2000 in Christchurch discusses the issues: https://www.canterbury.ac.nz/media/documents/event/Hopkins-L... The article is relevant because Christchurch had a major earthquake in 2011. I know of quite a few older buildings that were retrofitted that did not even need to…

Yes, in known earthquake zones I would expect some testing, but in places like NYC I'm not sure. In a few minutes searching I didn't find any reference to required testing of old buildings for structural or materials integrity.

In many parts of North America, testing and upgrades are only triggered with a change of use, or if required by buyers during sale of a building. The state does not maintain any kind of testing program of private buildings.

One exception is the mandatory retrofit programs implemented by some cities like San Francisco and Los Angeles.

Re: The problem with reinforced concrete (2016)

#160

Post by zelon88 »

mdgrech23 wrote: post #91
quickthrowman wrote: post #50

Earlier quoted context omitted.

> The cheapest bidder will generally win and their building will last the "design life" of the building, but often not much more. The simplest way to change this is to extend the design life, which would result in stainless steels or another more expensive material being used in this application. Just FYI, on a ‘plan and spec’ construction project, all material is specified by the architect and engineers. If the proj…

I'm not in traditional engineering but I always felt like "specs" only tell part of the story. In your example they may use stainless steel but cut corners by using less of it than they really should or maybe just use really cheap stainless steel which leads to other problems. I've noticed manufacturing companies like big auto will try to solve for this by creating more specs for parts provided by suppliers but that'…

Most manufacturing specs in US industries such as aerospace and defense are extremely well defined. They don't usually leave enough meat to cut corners in significant areas. They are typically fairly robust in that they are self-assuring. When specs are written correctly they are extremely difficult to subvert in one area and still come up with anything that could be confused with a conforming product. Plus the penalties for actively subverting these specs can be quite severe.

That said, I can almost guarantee the specs for automotive manufacturers are less strict and the penalties less severe simply because the specs are made to be cost-centric rather than performance-centric.

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