The most recent RUPD standard mandates a substantially stronger structure than its predecessors, making high-strength steel tubes the ideal choice for this purpose. 

By incorporating Strenx® 700 and Strenx® 960 steels in the main cross beams and support legs, the structure achieves the required strength while maintaining a reasonable weight limit. The SSAB tubes portfolio offers a variety of high-strength steel tube dimensions in rectangular, square, or circular shapes. All are specifically engineered to meet the RUPD standard requirements.

It is important to note that RUPD performance depends on the overall behavior of the structure, not only the crossbeam. Consequently, the connection between the crossbeam and support legs, the support legs themselves, and the connection between the support legs and the chassis should be considered carefully during the design stage. 

While the RUPD structure might possess adequate strength to endure the specified loads, the primary beam of the chassis could experience failure. To address this issue, reinforcing the chassis main beam through the incorporation of local stiffeners or employing higher grades of steel in the chassis can provide effective solutions.

Adding extra stiffener to strengthen the structure where the crossbeam connects to the support legs can effectively prevent or delay local buckling of the crossbeam and improve the load-carrying capacity of the RUPD (1). On the downside, this solution might allow stones or dirt to gather. Adjusting the stiffener by tilting it downward can fix the problem (2).

Rear underrun protection devices with support stiffeners leaning up (1) and down (2).

Equivalent strains.