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The expansion joints consist of structural openings designed to support the movement in a controlled way and, consequently, prevent any damage to the internal and external finishes of the bridge structure.The expansion joints play a role of fundamental importance in safeguarding the durability of the bridge by allowing the relative movements between the structural elements (vertical movements), due to variation of the deformation state to the variation of the applied load, to shrinkage phenomena and thermal gradients, preserving the regularity of the road surface.
The project consisted in the installation of a crash cushion to protect a cusp on a ramp with expansion joint, located on the State Road 76 of the Val d’Esino, near the “Jesi Est” exit, which is one of the main road axes between the regions of Umbria and Marche.
Installing a restraint system close to an expansion joint always presents considerable criticalities, especially because it hinders the anchoring of the device to the ground to allow the movement of the ramp.
It is therefore not conceivable the standard solution that involves the use of a reinforced concrete slab, nor is it possible to anchor to the asphalt surface by epoxy resin.
Fig.2 shows the detail of the anchorage.
The Research and Development department has studied a specific solution.
As it is not possible to use the traditional installation methods, the possibility of constraining the device on a galvanized steel plate was chosen, the latter constrained only on a ramp.
In the project illustrated the plate was constrained only from the side of ramp B (Fig.1) to allow the joint to expand. The crash cushion chosen in the specific case, among those is the Leonidas 80P.
The galvanized steel plate is bound to Ramp B through the use of 15 bars threaded with epoxy resin. For the realization of this anchoring system, static and dynamic checks were carried out.
During these phases, it was possible to evaluate the effect induced by the mass of the crash cushion on the anchor plate system plus chemical anchors in terms of displacement, stress and load on the threaded bars.
As a numerical analysis, a crash test TC 4.2.80 (side impact with vehicle mass 1300kg) and a test TC 1.2.80 (frontal crash with vehicle mass 1300kg) were carried out.
The TC 4.2.80 crash test is required by EN1317 and is the most critical test in terms of stress of threaded bars.
The versatility of the solutions proposed by SMA enables the road designer to always have a restraint device suitable for the protection of the fixed obstacle.
SMA’s Research and Development Department constantly collaborates with customers in order to always guarantee the highest level of safety for motorists in compliance with the criteria of compliance with the expected standards.