The test setups and calibration tests were carried out with the collaboration of the graduate student Lemuel González, the laboratory technician Camilo Medina, and the undergraduate students Andres Matos, Christian Flores, Richard Rodriguez, Samuel Montalvo and Steven Aviles.

Two calibration hybrid tests were performed at the UPRM hybrid simulation facility to ensure that all the equipment and software were functioning adequately. The calibration tests were executed by Dr. Shawn Gao from MTS systems. The tested prototype, shown in Figure 1, is a two-dimensional 3-story 2-bay moment resisting frame modified from a previous study on hybrid simulation by [9]. The story height and bay length are 15 ft and 30 ft, respectively, for total height of 45 ft and a total width of 60 ft. The beams and columns sections were modeled with elastic beam-column elements with concentrated plasticity represented by as zero-length elements with deterioration parameters attached to both ends of each beam-column element. Deterioration parameters were defined using the modified IK deterioration model, modified by Lignos & Krawinkler (2011) [10].

Figure 1 Prototype dimensions and sections. [4]

Two different test setups were tested for the calibration tests. The experimental substructure was the rightmost column of the first story. The rest of the structure was modeled using the software OpenSees. Based on a Finite Element Analysis (FEA) of the prototype and the capacity of the actuators, a scale 1:4 was selected for the test specimen, which is a W6x20 steel section. To avoid permanent damages on the test column, clevises were used at bottom of the columns. Clevises consists of steel plated joined by a pin with pair of steel coupons (steel rods) between plates to simulate the moment capacity of the column.

The test setup 1 consists of the first story column of 3.75 ft height (scaled 1:4 for prototype story height of 15 ft) with a clevis at bottom and a 244.31 MTS hydraulic actuator at top. The test setup 2 is the first story column (similar to test setup 1) with a half column (1.875 ft height) of the second story with a clevis at bottom and a 244.22 MTS hydraulic actuator at top. Figure 2 and Figure 3 shows a diagram for the test setup 1 and 2, respectively. The test setup 1 was used for the Conventional Substructuring Technique (CST) while the test setup 2 was used for the Pinned Substructuring Technique (PST).

The Conventional Substructuring technique (CS) intends to enforce compatibility and/or equilibrium in all DOFs at the boundaries of the partitioned structure. For the first hybrid test of test setup 1 with CS technique just the horizontal displacements were transmitted from the numerical substructure to the experimental substructure, and the forces were transmitted in opposite way. The Pinned Substructuring technique (PS) assumes pins at the points of inflection of the columns and beams. This point was selected to be the midpoint of the second story column. The second story half-column provide rotation to the first story. For the second hybrid test of test setup 2 with PS technique both displacements and forces were transmitted between numerical and experimental substructures, similar to the first hybrid test, but in this case for the first story and the half of the second story.

Figure 2 Test setup 1 for conventional substructuring technique. [4]

Figure 3 Test setup 2 for pinned substructuring technique. [4]

The prototype was subjected to the Canoga Park ground motion. Intensities of 20 and 40 % were tested for the test setup 1 and 2, respectively.  The following plots shows the results for the hybrid tests. They include the displacements and forces of the interfaces nodes (first story and half of the second story). The legends include: Pure FEA – pure finite element analysis of the prototype, ExpInterf – numerical substructure of the hybrid test, ExpCtrl – quantity sent from the numerical substructure to the hydraulic actuators, and ExpDaq – quantity measured by the hydraulic actuator. The displacement and force plots shows a good match between the pure FEA and the experimental results for both hybrid tests.

Fist Hybrid Test – 20% Canoga Park – Test Setup 1 – 1 Story Hybrid – Conventional Substructuring Technique

Second Hybrid Test – 40% Canoga Park – Test Setup 2 – 1.5 Story Hybrid – Pinned Substructuring Technique