WATCH: Engineers move 8000 tonne bridge 14m sideways in Western Cape

T_d_T_M

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You seem to know your stuff.
I was wondering why they don't just build next door to the old bridge and then shift the road there? Wouldn't that be a lot easier/cheaper than moving the bridge?
It depends on the situation. I'm not familiar with the Site and its various requirements but there would be some reasoning for this - i.e space, the construction of the arches, traffic accommodation or some other practical constraint.

Bridge's and especially large bridges like this have a ton (no pun intended) of thought provided into them before even the design is undertaken (let alone construction, although the two are linked). I haven't read the report governing the bridge nor am I familiar with the authority (i.e SANRAL or Western Province Department of Transport) behind the bridge.

Road realignment could be a feasible alternative, but I'm not familiar with the project to speculate - roads are generally a lot cheaper than bridges to construct for a given length
 

Gordon_R

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It depends on the situation. I'm not familiar with the Site and its various requirements but there would be some reasoning for this - i.e space, the construction of the arches, traffic accommodation or some other practical constraint.

Bridge's and especially large bridges like this have a ton (no pun intended) of thought provided into them before even the design is undertaken (let alone construction, although the two are linked). I haven't read the report governing the bridge nor am I familiar with the authority (i.e SANRAL or Western Province Department of Transport) behind the bridge.

Road realignment could be a feasible alternative, but I'm not familiar with the project to speculate - roads are generally a lot cheaper than bridges to construct for a given length

Western Cape government, provincial roads:

Edit: The bridge even has its own website:

Explanation of flood risk:
The original earth-filled multiple arch bridge at this crossing was constructed in 1930 for single lane traffic. In 1950 a substantial structural retro fitment that allowed two-way single carriageway vehicular and pedestrian traffic was undertaken. The superstructure was modified to a cast in-situ beam and slab configuration that maintained portions of the old arch superstructure, including arch-profile and related hydraulic opening configuration. The 1950 upgrade was however retained at an elevation which still resulted in overtopping with enhanced flood risk to the road and adjacent residential properties. The high river debris load combined with deep deck and wide solid wall piers, orientated at unfavourable skew angles relative to the flow direction, exacerbated the effects of flooding.

Photo of 2003 flooding:
e6ac791e3cdb4905979b9a95f4c37fa6.png


Key considerations for the latest upgrading was to minimize flow restriction and improve the available free board within the restrictions of adjacent properties and road alignment levels. Through an economic analysis, the technical options for the river crossing and construction strategy were evaluated with due consideration of the impact of construction strategy on road user costs.

Full design overview included, with this table:
0b8255560b2240e1b6c03295144f61f7.png


And the OP was wrong, it weighs 8000 tons:
Using a transverse launching method of a completed concrete tied-arch road bridge is a first in South Africa when more than 8000 tons of concrete and steel is moved over a distance of 24m in less than 24hours after several years of meticulous planning, design and construction.

Edit: I have no idea where the 400 ton number comes from. Perhaps that is the safe working load (capacity), not the weight of the bridge...
 
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gottagoon

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You can come back from retirement and help us reach that glory bra.
It's not something I did or could ever do. I'm not an engineer. However, South Africa had people that did these amazing things not so long ago.

Much respect to them :thumbsup: :cool:.
 

surface

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It's not something I did or could ever do. I'm not an engineer. However, South Africa had people that did these amazing things not so long ago.

Much respect to them :thumbsup: :cool:.
alas. I had high hopes. Our problem is that our most enormous talent in engineering is sitting in France and fighting covid vaccines and other brilliant polymath cannot get job here because of BEE. Both are prolifically active on mybb.

Now what do common people like you & me should do? That is the big question.
 

gottagoon

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alas. I had high hopes. Our problem is that our most enormous talent in engineering is sitting in France and fighting covid vaccines and other brilliant polymath cannot get job here because of BEE. Both are prolifically active on mybb.

Now what do common people like you & me should do? That is the big question.
For one lol, I'm too old at 58 to be accepted anywhere in the world. So I'm stuck here in SA.
 

The Free Radical

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I don't know how that ridiculously expensive monstrosity was ever approved by the DA Department of Roads. There was no need to move the bridge, instead they should have built it in its final resting position from scratch.
There was absolutely no need to build a bridge that expensive (R88 million) and technically complex, or to hire German and Swiss engineers to oversee it.

Some politicians and administrators definitely got their pockets lined on this fruitless and wasteful spree.
 
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rh1

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I don't know how that ridiculously expensive monstrosity was ever approved by the DA Department of Roads. There was no need to move the bridge, instead they should have built it in its final resting position from scratch.
There was absolutely no need to build a bridge that expensive (R88 million) and technically complex, or to hire German and Swiss engineers to oversee it.

Some politicians and administrators definitely got their pockets lined on this fruitless and wasteful spree.
I am not an engineer. How much should a bridge cost? And would it have been possible to build the bridge without closing the road down?

There is engineers within PWGC who should be looking at this to ensure that the budgets are not inflated. Maybe you are right.

But, PGWC 13 departments generally get unqualified opinions by the AG, and tenders are one of the things audited.
 

Priapus

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I don't know how that ridiculously expensive monstrosity was ever approved by the DA Department of Roads. There was no need to move the bridge, instead they should have built it in its final resting position from scratch.
There was absolutely no need to build a bridge that expensive (R88 million) and technically complex, or to hire German and Swiss engineers to oversee it.

Some politicians and administrators definitely got their pockets lined on this fruitless and wasteful spree.

So are you a bridge expert and do you have full knowledge of the site and requirements for the project?

I'll guess no...
 

Gordon_R

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So are you a bridge expert and do you have full knowledge of the site and requirements for the project?

I'll guess no...

The link I posted earlier on this page gives an exhaustive analysis of where, when, what, and how it was done. I guess that comment was made without reading the thread:
 

Rocco1

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The bridge became more expensive (though was the most expensive construction choice, but 2nd best for indirect impact and cost) because the orginal winner of the bid, Basil Read filed for bankrupty (protection) 1yr into the project, and Prov Gov had to go out on a second urgent tender to try complete the bridge, at a more expensive delayed price.
 

bwana

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Have we settled on a weight for the bridge yet?
 
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