RAILWAY BRIDGE CROSSING THE RIVER ALLER

Railway Bridge crossing the River Aller

Structural Monitoring at a Historical Vaulted Bridge

Initial Situation

The existing railway bridge is a vaulted multi-span bridge consisting of brickwork and has been erected in 1867. The flood span has been refurbished by a steel superstructure in the 20. century. The building transfers the important and highly frequented route from Wunstorf to Bremerhaven crossing the river Aller and its flood area and is an important connection to the international port Bremerhaven.

The vaults of the building are marked by damages in the brickwork and significant cracks which result from the high wetness and the associated frost impact. After 150 years the building has reached its service life. For this reason a new bridge will be erected next to the existing old bridge.

Because of the close proximity of the building site to the existing building direct and indirect influences concerning the old building couldn’t be excluded during the foundation works.

Because of the fact that during the building process the railway operation on the building had to be ensured the DB Netz AG decided to carry out a supplementary structural monitoring during the building period at the existing building.

 

Goal

With the monitoring installation significant changes in the existing building can be determined during the works at the foundation in time. A three-step warning- and alert-system has been installed to secure that those who are involved will be informed promptly and counter-measures can be launched if needed.

 

Monitoring System

In selected jeopardized areas of the bridge the settlements will be observed with the system of the electronic hose leveling. The development of the cracks in the arches and the deformation of the front walls will be acquired by using laser distance sensors. All measurements will be collected in a centralized data system and can be retrieved by those involved over an online portal at any time. So, deformations because of the building process can be noticed and rated very quickly by the building inspection, the project management and the facility operator. Dangers for the building resulting from settlements, developments of cracks and tilting will be reported by the alarm and the limit value before they will be visible.

During the pile driving process for the new bridge vibration measurements will be carried out at the vault piers with tri-axial velocity transducers. The possible transfer of vibrations will be observed and damages in the existing building caused by concussions will be avoided.

In the South a 600 m long embankment is affiliated connecting the Aller and the Wätern Bridge. Regarding the ground works settlements can’t be ruled out. To ensure safe railway operations the behavior of the embankment during the building period will be observed with a settlement monitoring using an electronic hose leveling.

Width: 
9,00 m
Height: 
5,00 m
Length: 
376,00 m

Construction:
multi-part railway crossing

Location:
Nearby Verden (Aller) on the route 1740 Wunstorf - Bremerhaven Seaport in km 85.024

Southern flood bridge:
Seven-span vaulted bridge (7 x 16.36 m)

Middle part:
Seven span steel deck bridge with open-track railway (3 x 16,36 m 32,72 m + 3 x 16,36 m)

Northern flood bridge:
Eight span vaulted bridge (8 x 16,36 m)

Length:
376.3 m

Year of Construction:
1867

Activities Marx Krontal:
Development and tendering of a structural monitoring, determination of warning values and limits, evaluation of the monitoring results

Monitoring:
2012 until the end of 2013