PSI - Issue 64

Fernando Nunes et al. / Procedia Structural Integrity 64 (2024) 1081–1088 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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6. Experimental Analysis of Prototype Beams and Load Considerations under Simulated Conditions For the design under consideration, maximum load guidelines are not explicitly specified by codes but must align with standards for inspection and maintenance. Eurocode 1 advises a concentrated load of 1.0 kN at the cantilever end of an L beam for roof maintenance, along with a 2.4 kN distributed load, accounting for the weight of either three individuals or two individuals plus an additional 800 N load. For safety, a factor of 1.5 for variable loads is recommended by Eurocode 0 (European Committee for Standardization, 2002). Concurrently, experimental analysis of prototype beams under simulated conditions was conducted to assess the mechanical performance of the proposed system, focusing on both strength and deformation characteristics. These experiments entailed constructing prototype beams with precise dimensions and employing a Finite Element Method (FEM) computational model for validation purposes. The beams, characterized by an L-section with dimensions of 50x80 mm, a thickness of 6.0 mm, and a length of 1500 mm, were tested alongside a corroded HEB 300 profile, emulating conditions typical of historic riveted steel truss bridges. The connection between the L-beam and the HEB profile was facilitated using clamps, bolts, and nuts, with S235 steel used for the profiles, plates, and clamps, and grade 8.8 M12 metric bolts. Displacement measurements at critical points and the deployment of strain gauges allowed for a detailed analysis of the prototype's structural behavior, aiding in the validation of the employed FE model (Cabaleiro et al., 2023).

Fig. 4. Laboratory assays: (a) Assembly of the anchoring system with a regulation plate at the bottom; (b) Detail of the digital indicators' positioning with an adjustment plate at the top. 7. Experimental results The mechanical behavior of an L-beam structure under load was rigorously evaluated in a controlled experimental setting, focusing on strain responses at crucial points to understand the effects of load changes and adjustment plate positioning. Strain measurements were meticulously taken at the top near the clamp bolt hole and the bottom close to the dual bolt holes connecting the beam to the adjustment plate. With the adjustment plate set at its highest position within the slots, applying a point load at the beam's end did not exceed the material's elastic limit. The most pronounced strain occurred adjacent to the clamp bolt hole, resulting in a deflection of 11.4 mm at a load of 1.0 kN. Altering the adjustment plate to its lowest allowable position, the maximum stress was again noted near the clamp bolt hole without exceeding the yield point, leading to a slight increase in deflection to 12.3 mm for the same 1.0 kN load. Without the adjustment plate, deflection significantly increased to 19.3 mm under the identical load, illustrating diminished structural integrity. At a higher load of 2.0 kN, the material's yield strength was exceeded at the beam's lower section adjacent to the bolt holes for the adjustment plate, causing a permanent deformation of 2.4·10 5 . These observations underscore the critical role of the adjustment plate's vertical positioning on the distribution of stress and deformation of the L-beam under various loads. This provides valuable insights into the system's structural performance and durability, highlighting the importance of precise configuration to mitigate excessive strain and ensure structural longevity.