EXPERIMENTAL TESTS AND NUMERICAL SIMULATION OF THE PLASTIC CYCLIC BEHAVIOUR OF STEEL COUPONS

Abstract eng:
The cyclic response of steel beam-to-column connections under a cyclic sinusoidal loading history was studied. The experimental investigation included a number of full-scale specimens having a cross section of IPE240 or IPE300 and a height of 1.0m. This part of the specimen was rigidly connected to a much stiffer steel beam thus representing a steel beamto-column connection under investigation. Instrumentation was provided to record both the applied moment as well as the deformation of the specimen in the region of the connection in terms of plastic hinge rotation. Simple steel coupons were taken from these T-beam specimens after testing having the shape of an orthogonal prism. The cross-section of these coupons was 6.2mm x 8.0mm and their height equal to 16.5mm. Each coupon was extended at either end to a much larger and thicker part enabling its attachment to the loading ring which consisted of a dynamic actuator capable to apply the desired cyclic load with a sinusoidal distribution having a given amplitude and frequency. A number of such simple steel coupons were tested and their response is presented and discussed having as main variable the nature of the load (monotonic or cyclic) and the variation of the loading frequency. From the observed behaviour it can be concluded that an increase in the strain rate results in an increase of the stress values beyond the yield. Next, a numerical study is performed in an effort to simulate the observed behaviour of these simple steel coupons. It can be concluded that the combined constitutive law can be quite successful in yielding realistic prediction of the cyclic response provided the appropriate values of the parameters defining this constitutive law are predetermined for the strain rate at hand. The numerical predictions employing the isotropic hardening constitutive law do not achieve the same degree of agreement with the observed behaviour, especially when the comparison is made on the cyclic response results. However, this type of numerical simulation is generically sensitive to the variation of the strain rate effect through the option of the dynamic increase factor (DIF).

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