How much?

[Cdnwolf]

How much material would I need to bring down this bridge It is 1100 feet long reinforced concrete in sections. It will be done by special forces.

[Cdnwolf]

Now they definately are watching us!!!!

[kato13]

My answer would be probably less than you think.

Raw numbers for an answer would probably be ok, but jf there are specific instruction on how to make the demolition more efficient please keep it in PMs.

[pmulcahy11b]

If you ask a combat engineer, the answer will always be "Twice as much..."

[pmulcahy11b]

Now they definately are watching us!!!!

A component of my diagnosis is paranoia, so I always think they're watching us!

[leonpoi]

what might be useful is (from a source book that I can't remember, plus some of my own interpreation) the following roughly applies:

Penetration needed to take down bridges
Wood: 22-28
Stone: 45-55
Metal: 55-70

the higher range will take down the bridge on a success, the lower range will on an outstanding success.

Now I'm rusty on DP and Pen. but taking reo as metal we might decide we need 70 Pen (strictly according to the rulebook this would give 7x250mm reinforced concrete penetration). if the charge was somehow tamped then the Pen is doubled -> Pen 35 worth of explosives -> 96 DP. A 1 kg block of plastic is 6 DP -> 16 kg of plastic. Who knows if this is realistic, but ignorance is bliss using the min amount if 55/2 -> about 60 DP -> 10 kg. So 10kg to damage and maybe destroy, 16kg to destroy. The sourcebook stated that a damaged bridge will collapse if a vehicle >10 ton (or maybe it was 8, I can't remember) is driven over it (high chance of collapse, about 80%. A construction/CVE test to determine how much it can hold), or if damaged again. If you can't tamp then the DP to destroy is 392 -> 65kg, so I hope that you can rationalise a method for doing so.

I'm guessing that this amount would be needed on each pylon if you really wanted to make a mess.

[Legbreaker]

What exactly do you mean by "bring down"
Do you need the whole thing dropped into the river, pylons included
Would cratering the road surface so as to prevent movement of traffic for 24 hours (while the engineers lay a new temporary decking over the hole) be sufficent
Is the desired effect somewhere in the middle

Time available is also a factor. Using boreholes to place the explosives within the structure itself well require much less explosive than if it were just laid against the surface. Naturally boreholes take time (if drilled) or are exceptionally noisy (if blasted with shaped charges, which still take time for the holes to cool down and allow safe laying of the actual demolition charges).

So, what it really comes down to is what it the teams plan and just how much can they carry

[jester]

To many factors to give one answer. If I had time there are things I would do to make it much easier and thus require less demo. If you are using stealth to deal with to avoid any enemy sentries and such then you will have to do it old school and use ALOT!!!!

Some examples of bridge and other structure demo, just watch an implosion or the flick "Force 10 From Navarone" which will answer alot.

[Targan]

I think it would be dangerous and unwise for me to go into too many specifics about how to take down a bridge such as that but I would ask similar questions to Legbreaker's - how much of the bridge do you want to damage or destroy. If the goal is to breach at least part of the span and make it very difficult and expensive to repair, taking down one or both of the two main supports in the river would be the way to go but that would be a major undertaking. You would need many men each carrying alot of weight in tools and explosives.

How about floating a raft or barge down the river, packed with a tonne or two of ANFO Tie that to a pylon and let it off and it would very likely destroy the pylon and drop the bridge and the prep time at the target would be only seconds or minutes (not including the getaway time).

[Cdnwolf]

The bridge would be the only remaining one crossing the Danube river and the only supply route for the Russian armies attacking Vienna - gone as in no chance in hell of replacing it. So basically is a suicide mission .... but nothing the characters can't handle!!

[Ramjam]

Just use a nuclear demolition charge like the US Army did in Black Madonna.

It's the only way to be sure.

[smokewolf]

The bridge would be the only remaining one crossing the Danube river and the only supply route for the Russian armies attacking Vienna - gone as in no chance in hell of replacing it. So basically is a suicide mission .... but nothing the characters can't handle!!

If this is your goal, as a former combat engineer I'd recommend that you don't want it gone completely.

You have three basic options:

1) Blow it to smithereens.
2) Damage it just right that it's both unusable and unsalvagable.
3) Weaken the bridge supports using cutting charges

Option #1 - with the bridge out of the way the Russian then move in pontoon bridging boats to construct a make shift bridge and continue on. While you will definitely have slowed them down, you've only done so by the time it takes them to move the pontoons to this area.

The task though will more than likely take your players more time and explosives to accomplish than the Russians replacing the bridge.


Option #2 - You blow only a small section of the bridge such that it twists down into the water. This requires a much smaller amount of explosives. The current of the water then works on the bridge and causes it to twist, break and contort enough to not only be unusable but unsalvagable. The Russians can still construct a pontoon bridge or equivalent across it, but in order to do so they must first demolish the remaining bridge.

This task should be quicker and cost less in explosives than Option #1 and will cause the Russians to spend more time and their own explosives to blow the remaining bridge.


Option #3 - You place explosives at key points on the bridge to weaken but not destroy it. When the Russians move their convoy across it next, it results in Option #2 but it takes a good portion of the convoy with it.

This task should be even quicker and cost less in explosives than Option #2

[jester]

Lets look at some of the attempts by the Germans to take out the railroad bridge at Remagen.

Shelling it is costly, it would take pinpoint accuracy and lots of shells. Are the resources available And would the Russians mount a counter attack

Scuba divers with demolition charges on the underwater footings. This is possible, but is it practical Do you have well trained divers and knowledge of the bridge and the pillings and riverbottom material And of course a launch point that is secure to launch your forces from And of course the materials, scuba or more likely rebreater gear, wet suits or dry suites, lights, timmers, igniters, lots of det cord to connect the charges and to use as wrapping to cut steel beams. And, of course the amount and quality of the explosives.

A comando force can sneak in and place charges on the reinforcing beams they can do this stealthfuly, placing them surgicaly, wraps of det cord and specific ammounts of charges in the support structures and key points that will allow it to fall under its own weight. The down side, you need to be stealthy and if caught you are screwed, or doing everything underfire which of course will cause the chances of failure to increase.

Or, just sieze the bridge! Go in, sieze it. On force conducts a holding action against the Russians trying to retake the bridge. A second force goes to work with torches and placing demolitions to weaken the bridge and ensure it falls when the charges go off. Downside, it can be a suicide mission for those on the bridge. They sit tight until it blows. OR, they can either escape via boats they have waiting below the bridge, or simply dive into the water and swim for it. Of course to ensure that is successful, you would want to place ALOT of anti personel mines and booby traps to slow up the enemy so they do not make it to tamper with your main charges.


As for me, I'd go for the stealth aproach. Wetsuited combat swimmers with demo packs placing the charges at the bridges footings where the steel meets the concrete and tamp them. If the footing of the bridge is parted it will come down. I would also use thermite bombs and det cord to cut through alot of the support beams. The cool thing, you only need to attack one side of the bridge, left or right side, one side of the bridge comes down it is unusable, all the forces will take it down, as you have longer spans that are unsupported. And when it comes time to rebuild, you still have 1 side still standing to possibly use should you want to rebuild.

Also, it would be a good idea to somehow cut the upper supports atop the bridge as they tie in alot of the support for the bridge.

Anyhow, those are some of the ways I would take it down. As for suppliest 2 dozen thermite grenades, 4 to six rolls of detcord, 8-12 satchell charges, 8 waterproofed satchell charges with enough detcord to connect them and two timers and shock cord or instant fuse.

Working primarily on one side, the upriverside would be my choice so you have the forces of the water working for you once the charges do blow.


1.) Thermite bombs go off burning through support structures that they are best suited to cut through. Lesser beams, steel support cables and similiar.

2.) Cutting charges blow cutting support structures, supporting and reinforcing beams and such.

3.) Cutting charge at the footing goes, this will cut the steel vertical girders that support the bridge.

4.) Underwater charges under the concrete footing supports go, these give the bridge one last shack to rock things loose, further break what has been cut and weakened, and blow away more of the concrete footers which coupled with the steel supports which have been cut or weakened should be enough to tumble the spans into the water. <Its kind of like chopping a tree, how a logger will notch it before starting on the primary cut, if we can eliminate first foot or so of the support pillars it will fall giving that much more stress on the already weakened structure>

The longest phase of the explosion will be the termite bombs burning, then after about 20 seconds of the thermite cutting, the charges go off in the order they are posted with three to five second intervals.

The danger, one explosion could damage the other charges, this they all need to be in independant systems as well as redundancy.

Anyhow, those are some of the things I'd think of and possibly try.

[Legbreaker]

My thoughts are that unless you've got a LOT of time AND explosives available, the piers aren't worth troubling with. Build to withstand not just the weight of the bridge, but flood waters as well, unless they've been constructed with demolition chambers built in, they're not going anywhere in this lifetime...

[jester]

I mean the steel structure above the piers, the piers or pillings are usualy concrete, and the footing of the bridge is usualy steel imbeded into the concrete. Where they merge however, you have to different materials joined, and that is usualy the weak spot. A meter or so up and you have all those stresses. The charge on the concrete pilling is more to cause a shacking of the bridge once its been damaged to help loosing up what has already been damaged or weakened by the prior explosives so that gravity can do its job.

Also, look at places where a steel pole is imbeded into concrete, there is always rust on the steel, again a weak spot that should be checked and exploited.