Viaduct SS335 (case study)

The SS335 is a prestressed concrete bridge built in the early 60s, composed by two independent carriageways, each having nine simply supported spans. The structure is locatel along the A32 highway connecting Turin to Bardonecchia. The typical span is 35m long with a cross section made by a prestressed concrete slab having constant height of 1.5m.

Object description

(No object description available.)

Civil engineering type

:

Road network Bridge

Year of construction

:

1960

Composed of materials

:

Prestressed concrete

Location coordinates

:

45° 2' 26.67" N, 6° 49' 30.39" E

Country

:

Italy

View civil engineering work details

Loading map...

{"minzoom":false,"maxzoom":false,"mappingservice":"leaflet","width":"auto","height":"350px","centre":false,"title":"","label":"","icon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"zoom":false,"defzoom":6,"layers":["OpenStreetMap"],"image layers":[],"overlays":[],"resizable":false,"fullscreen":false,"scrollwheelzoom":true,"cluster":false,"clustermaxzoom":20,"clusterzoomonclick":true,"clustermaxradius":80,"clusterspiderfy":true,"geojson":"","clicktarget":"","imageLayers":[],"locations":[{"text":"\u003Cdiv class=\"mw-parser-output\"\u003E\u003Cp\u003EViaduct SS335\n\u003C/p\u003E\u003C/div\u003E","title":"Viaduct SS335\n","link":"","lat":45.04074166666667,"lon":6.8251083333333336,"icon":"/images/imsafe/c/c8/Blue-marker.png"}],"imageoverlays":null}

Object analysis

During the strenghtening works the clinometers raw data were analyzed to evaluate the plastic deflection recovery after the external pre-stressing was applied to the deck. Vibration-based damage detection techniques were used to identify the changes in the dynamic response of the system, such as Operational Modal Analysis (OMA) techniques, Power Spectral Density (PSD) and Frequency Domain Decomposition (FDD). A stable peak-picking analysis has been performed to track the natural frequencies evolution in the long-term period. Non-Linear Finite Element Analysis (NLFEA) and a model updating procedure were used to simulate the bridge behavior both in damaged and strengthened state. The FE model was also used to simulate a set of possible damaged scenarios to calculate the thresholds in terms of plastic rotations and frequency shifts for the long-term monitoring.

Case type

:

Consulting

View analysis details

Object state

Following an inspection, some cracks were found at the inner surface of the slab, due to the failure of a significant number of pre-stressing tendons caused by a diffuse corrosive phenomenon. Strengthening works were necessary, the solution chosen was the adoption of an external pre-stressing system. The Sacertis SHM system installed in April 2019 was developed for both the short and long-term monitoring. Each span is equipped with a chain made by five biaxial MEMS clinometers and five triaxial MEMS accelerometers. The system is completed by two gateways, one per carriageway and a power line communication to connect all the devices to the network. In each sensor box are present a temperature and humidity detectors. Prior information available were: drawings, design documents, results of thorough investigation of the damaged span. A calibrated non-linear FE model based on the static load test and dynamic characterization of the structural response (in both the damaged state and after the strenghtening works) has been used to determine the warning and alarm thresholds levels.

Observed deterioration processes

:

Chloride induced corrosion

Observed damage types

:

Local rupture or failure, Cracks

Performance indicators

:

Deformation, Displacement, Dynamic response (acceleration/damping/frequencies), Material mechanical properties, Cracks (width/length/pattern)

View object state details

Images

Documents

This case study was contributed by Paola Darò of SafeCertifiedStructure Ingegneria S.r.l.. Last edited by technical staff.