zlacker

> Reinforced concrete seems to do exactly what it's intended to do for the designed life of that intent

Until there's apparently "no money" to replace the structure after its design life time. Thinking in decades of life span for many of these structures is very short sighted. I think the article mostly gets that across i.e. re-enforced concrete is hard to recycle and their life span is often within that of a human life. We should be able to do better and create large scale structures that can not only serve a purpose over several life times, but can be added to or enhanced rather than demolished.

The only reason we keep building these time limited structures is because building codes still allow this, which leads to easy short term profits, and it's "someone else's problem in 50-60 years time". There's no incentives.

>>teh_kl+(OP)
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 future loading - how much traffic, what kind of trucks at what weight, etc.

We'd all be much better off increasing maintenance budgets to extend the lifespan of existing structures without completely re-doing them at multiples of the current price.

>>LegitS+Kd
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"

>>Clumsy+Un
> 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.

>>LegitS+Bo
"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"

>>Clumsy+7p
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.

>>teh_kl+(OP)
I think many commentators, including yourself, have an erroneous assumption about structural design which is roughly summarized as: the inputs are known with certainty. This is really not the case especially when considering natural hazards like wind and earthquake. What happens to your 500 year lifespan design when we discover new information about earthquakes at the site. This is happening regularly with every building code update. Our design loads change To reflect the latest research on things like seismicity. When you factor in this consideration, it may actually make a lot of sense to only design for shorter lifespans.

>>LegitS+ur
Welding rebar is almost never used in North American building construction, and is actually forbidden in high seismic zones.

But then again so is stainless steel rebar and carbon fibre rebar and most of these other types of products because they lack ductility

>>ggcdn+ju
This is kind of what I was thinking while reading comments here.

I'm sure stainless rebar is easy to make. We could turn out huge amounts of it. But I don't see it ever having the same useful properties. All manner of stainless I've worked with is incredibly stiff and hard compared to regular steel. It's actually desirable in most applications, but rebar in particular needs to be flexible.