PSI - Issue 75

Bruno Depale et al. / Procedia Structural Integrity 75 (2025) 254–261 Bruno Depale/ Structural Integrity Procedia (2025)

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cycling loads in the main part of LBB. It also weakens the buckling strength of the beams and increases the probability of fatigue cracks. Due to that, we will have to include corrosion models in this study.

Fig. 2. Long Bien Bridge, now, right bank.

3. Fatigue loading of Long Bien Bridge We have limited this study to: •

the central part of LBB because it is the main load-carrying structural part and consequently to fatigue damage due to railway traffic, voluntarily neglecting both side paths added in 1924, • the first six spans of right bank, because they belong to the original design of LBB.the dynamic effects are not taken into account because of the low limit speed on LBB (15 km/h).

3.1. Railway traffic and train line-ups during the French domination (1903-1954)

For the RLA of LBB, only the railway traffic is considered, because it is a variable loading, when wind loads, or temperature variations are neglected. LBB belongs to the Hanoi – Lao Cai – Hai Phong railway line and the data collection regarding the railway traffic for this study is complex because this line was used for a variety of purposes, e.g., civilian, military, agricultural, industrial or mining. We have analyzed the archives of ANOM ( Archives Nationales d’Outre -Mer ) located at Aix en Provence (France) and from that material we could get a first set of assumptions, distributing the various types of trains into four main categories: see example in Fig. 3. This figure shows that during the 1912-1938 period, the traffic increased significantly with respective fluctuations depending on the type of trains. We have not considered specifically the tramways and railcars circulating on LBB, due to their light weight. From the statistical colonial data of the traffic collected at ANOM, we can establish a first series of four train line-ups, for the period 1903-1954. Their respective numbers of coaches and wagons are described in Table 1. From the same data, we were also able to determine the average transported weight for each type of train carriage or freight car, per train line-up, with a reasonable conservatism. As a result, Fig. 4. gives the train line-up of departmental trains.

Table 1. Train line-ups during French domination.

Type of train

Passenger trains Mixed trains

Mixed trains

Mixed trains

Freight trains

Depart. trains