PSI - Issue 44

Agnese Natali et al. / Procedia Structural Integrity 44 (2023) 2326–2333 Agnese Natali, Francesco Morelli / Structural Integrity Procedia 00 (2022) 000–000

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sensors are placed to measure the relative deformation of the end sections of the diagonal. The load is directly measured through the universal machine (Fig. 4b). • “AD HOC TESTS”, where each diagonal is tested in its actual configuration (Fig. 5a). A dedicated test set up is prepared to test each component in monotonic tension, monotonic compression, and cyclic loading (x2). The purposes of the test are to observe the behavior of the whole subassembly, to see if the design rules for the POS are actually respected and if the safety coefficient for the design of the over-resistant components are sufficient to guarantee the desired behavior: bearing of the diagonal connection (diagonal side) should be reached first, other damage in connection (shear failure of bolts, damage in upright due to bearing, failure of diagonal net section) and buckling of diagonal in compression should be prevented or in any case anticipated by over-crossing bearing resistance of the diagonal element. The configuration of the test set up is showed in Fig. 5b: load is applied through the hydraulic actuator, which is supported on one side by a “contrast” structure, and on the other side is connected to a pinned column. The top upright of the specimen is connected to the pinned column or to an intermediate piece that is integral to it, and the base upright is connected to a column that is fixed to the basement of the set up. The pieces to connect the specimens to the set up are adjustable, in order to have the necessary flexibility to fit the different geometries of the specimens. For each test, load is measured by a loading cell, and various displacement sensors are placed to control the total and global deformation of the diagonal. The cyclic test loading protocols are two: the first one is the standard one, as defined by the ECCS “Recommended testing procedure for assessing the behavior of structural steel elements under cyclic loads” (1986); the second protocol is called “ failure-consistent ”, and it is derived by conducting statistical analysis on the seismic response of a realistic double-depth ARSW designed according to the POS.

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Fig. 4. UNIVERSAL MACHINE TESTS: (a) varying parameters for the different configurations for the tested components; (b) global view of the test set up.

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Fig. 5. AD HOC TESTS: (a) Scheme of the ARSW frame from which the diagonal-to-upright is taken; (b) general view of the test set up.