Development of a ten‐element hybrid simulation platform and an adjustable yielding brace for performance evaluation of multi‐story braced frames subjected to earthquakes

Self Cite

In a building subjected to seismic loading, large compressive force may develop in reinforced concrete (RC) coupling beams because of axial restraint imposed by the neighboring shear walls against the elongation of the coupling beams during the failure process. The axially compressive force can increase the shear stiffness and strength of the coupling beam and may change its failure mode. In this paper, a novel coupling beam testing procedure adopting hybrid simulation method is proposed in which the axial restraint is determined through hybrid simulation and the calculated axial restraint is imposed on a specimen during the test. RC coupling beams were tested by adopting both the proposed test procedure and the conventional testing approach in which the effect of the axial restraint is not accounted for. Test results depict a clear difference in the response of the coupling beam, such as shear capacity and failure mode, depending on the consideration of the axial restraint during the test. The test outcome demonstrates the usefulness and applicability of the proposed test procedure.

Section: Experimental Programmentioning

confidence: 99%

Section: F I G U R E 7 Conversion Schemes Between Numerical and Expermentioning

confidence: 99%

Application of hybrid simulation method for seismic performance evaluation of RC coupling beams subjected to realistic boundary condition

Park

Στρεπέλιας

Stathas

et al. 2020

Self Cite

“…Experiments are highly effective for examining the seismic performance of structures. Pseudo-static (cyclic) tests with a prescribed loading pattern are often used to investigate the structural bearing capacity and/or deformation characteristics, whereas online hybrid tests 1,2 are used to acquire structural responses under earthquakes. Despite their different objectives, both testing methods require spatial loading in multiple degrees of freedom (MDOF) to emulate realistic boundary conditions at the loading points.…”

Section: Introductionmentioning

confidence: 99%

Multi‐degree‐of‐freedom force‐displacement mixed control strategy for structural testing

Zhou

Wang

et al. 2020

Structural members carry spatial loads owing to, for example, gravity, winds, and earthquakes. Loads along multiple degrees of freedoms (DOF) should be synchronously imposed on the loading point for accurately reproducing structural responses under spatial loading. Strong coupling may exist among the multiple DOFs owing to specimen rigidity, posing significant challenges for actuator control. Two major problems should be solved to address this challenge. The first is the nonlinear coordinate transformation from the local actuator space (LAS) to the global Cartesian coordinate (GCC) system, depending on the current GCC position of the loading point. The second is the mixed control scheme for engineering specimens, that is, force control in rigid directions and simultaneous displacement control in soft directions, which depends greatly on the nonlinearities developed in specimens. To overcome these difficulties, a modified Newton-Raphson (NR) iteration integrated with a PI control (MNR-PI) is developed to handle material nonlinearity, and the incremental kinematic transformation method integrated with PI control (IKT-PI) is proposed to solve the nonlinear coordinate transformation problem. The theoretical background of the MNR-PI, which can be synchronously incorporated with the control process of the loading system to solve nonlinear problems, is first provided. The control gains are then designed by discrete control theory, and a new MDOF force-displacement mixed control method is accordingly formulated and numerically simulated. Finally, three-DOF cyclic tests on a steel column are conducted to demonstrate the feasibility and accuracy of the proposed method.

“…In our knowledge, Kim et al describes one of the few successful attempts to include the axially loaded vertical DoF of the physical pier of a virtual bridge prototype in the HS loop. Comprehensive reviews of all control issues related to HS with stiff PSs are reported in Wang et al and Mojiri et al Besides adversely affecting displacement control accuracy, stiff PSs naturally increase the frequency bandwidth of the hybrid model, whose higher eigenfrequencies (divided by the testing time scale) may fall outside the frequency bandwidth of the actuation system thus destabilizing the HS. This is a collateral issue to which, in the authors' knowledge, no sufficient attention has been dedicated yet, and that this paper tries to address.…”

Section: Introductionmentioning

confidence: 99%

A model‐order reduction framework for hybrid simulation based on component‐mode synthesis

Miraglia

Petrović

Abbiati

et al. 2020

Testing of stiff physical substructures (PSs) still poses major technical issues that prevent from adopting hybrid simulation (HS) as a standard structural testing method. Firstly, elastic deformation of reaction frames, as well as the limited resolution of displacement transducers, deteriorate displacement control accuracy. Secondly, as a consequence of control errors, small perturbations of actuator displacements entail large restoring force oscillations that spuriously excite the higher eigenmodes of the hybrid model. For this reason, in the current practice, force-controlled hydraulic jacks handle vertical degrees of freedom, which are typically associated with stiff axially loaded members and excluded from the time integration loop. Vertical forces are either kept constant or adjusted during the experiment based on simplified redistribution rules. Besides deterioration of displacement control accuracy, stiff PSs naturally increase the frequency bandwidth of the hybrid model, whose higher eigenfrequencies (divided by the testing time scale) may fall outside the frequency bandwidth of the actuation system, thus destabilizing the HS. This is a collateral issue to which, in the authors' knowledge, no sufficient attention as been dedicated yet, and this paper tries to address it. From this standpoint, we propose component-mode synthesis as a rigorous approach for deriving reduced-order physical and numerical substructure mass and stiffness matrices that minimize the frequency bandwidth of the hybrid model. The proposed methodology allowed for performing HSs of a load-bearing unreinforced masonry structure including both horizontal and vertical degrees of freedom with a standard three-actuator setup used for cyclic testing.