Wildlife Crossing AM2 in Carinthia, Austria
Customer Project
Wildlife crossing AM2 was built using a construction method for concrete shell structures called Pneumatic Forming of Hardened Concrete (PFHC). This new method was developed by TU Wien in the context of the research project titled "Double Curved Shell Structures".
| Investor and Design |
Austrian Federal Railways (ÖBB) www.oebb.at |
| Geometry Optimization and Structural Analysis |
Technische Universität Wien Institute of Structural Engineering www.tuwien.ac.at |
The new bridge spans the new double-track line of the Koralm Railroad in the south of Carinthia. In order to test as many design details as possible, a first test shell on a scale of 1:2 was built, now being used as roofing for events.
Functioning of Construction Method PFHC
First, a flat concrete slab with wedge-shaped outlets, in which wedge-shaped air cushions are mounted, is cast. On the slab's edge, unbonded tendons are placed in sheaths. Subsequent to the concrete hardening, an air cushion lying underneath is blown up, transforming the concrete slab into a double curved shell. At the end of the transformation, the tensioning cables are additionally prestressed. They are anchored as soon as all the joints are sealed with concrete or grout.
Construction of Wildlife Crossing
The thickness of the transformed shell is 4 inches and supplemented by a concrete topping of 14 inches. Fine cracks arising during the transformation are sealed by this additional layer of concrete. The bottom side of the shell is free from cracks due to the compression zone located there during the transformation.
The entire shell structure of the bridge has ground plan dimensions of 120.5 ft x 127 ft and a height of 29 ft. Its shape is based on the supporting structure's optimization corresponding to the occurring loads and given boundary conditions. Due to this optimization, a state of membrane stress is reached which is favorable for the structural behavior.
The ecological balance of the wildlife crossing has been impressive. In comparison with a reinforced concrete frame originally planned as a crossing alternative, environmental pollution can be reduced by about 40%, evaluated with regard to the global warming potential (CO2 equivalents).
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Using "End Prestress" Load Type
Until now, the prestress load type had always been an initial prestress in Dlubal Software programs. The defined load magnitude was applied and, depending on the stiffness of the surrounding system, prestress remained more or less as an axial force in the cable.
Increased Calculation Performance by Reducing the Nodal Degrees of Freedom
The number of degrees of freedom in a node is no longer a global calculation parameter in RFEM (6 degrees of freedom for each mesh node in 3D models, 7 degrees of freedom for the warping torsion analysis). Thus, each node is generally considered with a different number of degrees of freedom, which leads to a variable number of equations in the calculation.
This modification speeds up the calculation, especially for models where a significant reduction of the system could be achieved (e.g. trusses and membrane structures).
- How can I display the deformation in the current construction stage and in relation to the initial system in RF‑STAGES?
- I have calculated a box girder. Which surface results or surface stresses can I use to evaluate the buckling behavior of the web plates?
- Is it also possible to specify a cable length in RF‑FORM‑FINDING?
- How is it possible to consider the real cross-section geometry of member elements in RWIND Simulation?
- Is it possible to define orthotropic surface loads in RFEM? I would like to subject a surface to different temperature loads by a direction.
- The calculation of my model results in unrealistically high stresses at many locations. What could be the reason for this?
- Is it also possible to enter the temperature for a surface in the XZ plane by using the height (variable in Z)?
- Does Dlubal Software provide any solution for composite bridge construction, or perhaps also verification examples or reference objects?
- In the case of the "Initial strain from other LC/CO" feature, I cannot retrace internal forces. How is this function mapped internally?
- Which analysis is used in RF‑STAGES or STAGES to calculate temporary loads and the generated combinations?
Programs Used for Structural Analysis
Main Program
Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids, and contact elements
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