Carbon Strips Buy the Výtoň Bridge Two More Years

Scaffolding is going up on the railway bridge at Výtoň this week, and from next week Správa železnic will start cleaning selected points on the steel structure and bonding carbon laminates directly onto them. The work will take six weeks. Nothing about the way the bridge is used will change: one train at a time, 20 km/h, with only a partial restriction on the walkways for pedestrians while the scaffolding is in place. Zdopravy.cz reported the start of the works on 8 September.

What the six weeks buy is time. The strengthening is intended to hold traffic in its present, heavily reduced form until at least 2028 — which is to say, long enough for the argument about what happens to the bridge to be settled.

Stabilising parts of the bridge is the most effective way of keeping traffic on it in the current limited extent.

— Nela Friebová, spokeswoman for Správa železnic

What is actually being glued on

The method is not new to the bridge's file. Last autumn Mojmír Nejezchleb of Správa železnic's line modernisation division described it to Zdopravy.cz as bandaging.

Strips of a special material will strengthen elements with fatigue damage. Under present conditions that will last 3–5 years.

— Mojmír Nejezchleb, Správa železnic

Pavel Ryjáček, professor at the department of steel structures of the Faculty of Civil Engineering at ČVUT, later set out the technique in more detail for the same outlet.

It consists in installing CFRP — carbon — laminates, laminated at the point of greatest degradation of the diagonals and at points heavily stressed in fatigue. The aim is to stabilise the condition at these critical nodes.

— Pavel Ryjáček, ČVUT

Two properties recommend it. It disturbs the bridge and the traffic on it very little, and the material is reversible: once Správa železnic's preparations for a reconstruction advance, the laminates can be taken off again. That matters for a structure whose future form is still open.

Experts from the same ČVUT department will supervise the installation. They also run the long-term monitoring of the bridge, and according to Ryjáček's statement in January the rate of degradation has recently slowed — a consequence of running on one track only and of the reduced number of trains.

The bridge that keeps splitting the room

Správa železnic says it discussed the works in advance with the heritage authorities, and it is worth reading that sentence as the diplomacy it is. A heritage working commission handed the infrastructure manager its conclusions this summer, finding that the bridge can be repaired. Ryjáček, a member of the group, objected to the final report and resigned from it. What followed, Zdopravy.cz reports, was a sharp exchange over how effective a reconstruction would be and how long the resulting service life would really last.

Správa železnic has spent recent months trying to normalise its relationship with the heritage side and is looking for a compromise between repairing the bridge and building a new one. Neither party is willing to discuss it publicly at the moment. The manager says it intends to decide on the final crossing solution this year.

Read together, the six weeks of laminating and the promised decision look like one plan: buy enough structural certainty to get past the deadline the argument has been running against.

Why one bridge matters this much

The crossing of the Vltava at Výtoň has carried trains since the beginning of the last century, and it sits on a busy line. Suburban services from Prague to Beroun use it, and so do long-distance trains to Plzeň and on into Bavaria. Every one of them currently crosses alone, at walking pace for a train.