PSI - Issue 5

José Santos et al. / Procedia Structural Integrity 5 (2017) 1310–1317 Pedro Andrade, José Santos & Lino Maia / Structural Integrity Procedia 00 (2017) 000 – 000

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Figure 6 – Numerical model of the step with the third reinforcement measure

Figure 7 – Numerical model of the step with the fourth reinforcement measure

 Reinforcement Measure 5 – Weld metal bars between the treads

The fifth reinforcement measure is also similar to the third reinforcement measure but rather than welding a metal plate between the treads, it consists of welding metal bars between the treads. This reinforcement measure was simulated in the numerical model connecting the steps with several metal bars modeled as frame elements. To significantly reduce the accelerations it was necessary to use 19 metal bars between each tread with an area of 20 cm 2 . This area as well as the number of bars is clearly excessive and can hardly be feasible.  Reinforcement Measure 6 – Place dampers between the treads The sixth proposed reinforcement measure consists of placing dampers between the stairs steps in order to increase damping and reduce vibrations. Numerically this solution was tested by defining dampers with a given damping value C (Ns/m) and modelling them between the treads. The accelerations were calculated for a different numbers of dampers, with different damping values C (Ns/m). It has been found that regardless of the damping value C (Ns/m) and the number of dampers used, the accelerations during the time the footfall force is applied never significantly reduce, decreasing sharply to almost null values only when the load ceases to act. In Figures 8 and 9 are represented the numerical models of the treads with the application of the fifth and sixth reinforcement measures respectively.

Figure 8 – Numerical model of the step with the fifth reinforcement measure

Figure 9 – Numerical model of the step with the sixth reinforcement measure

 Reinforcement Measure 7 – Weld a metal plate under the treads, forming a coffin

In the seventh reinforcing measure it is proposed to weld a metal plate under each tread, along its length. It is also suggested that a triangular metal plate, perpendicular to the latter, be welded in the middle of the treads. This reinforcement measure aims to significantly increase the stiffness of each stair step. Numerically the metal plate placed under the treads and the triangular metal plate perpendicular to it were modeled by shell elements with a thickness of 6 mm (equal to the thickness of the existing tread).