COMUNICACIÓN, EDUCACIÓN, PARTICIPACIÓN Y CONCIENCIA CIUDADANA

5.2.2.1 Horizontal Displacement of Cap and Superstructure

Each end of the bridge deck was mounted with a string potentiometer along its centerline in order to validate the displacement readings provided by the horizontal actuators as shown in Figure 5.35. On the reaction frame side of the test unit, an extra string potentiometer was added to the side of the deck in order to obtain an additional displacement and deck rotation reading. Additionally, each end of the cap beam was instrumented with string potentiometers in order to provide both the horizontal displacement of the cap in the longitudinal direction of the bridge and to indicate any twisting of the superstructure as shown in Figure 5.36.

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Figure 5.35: Location of Deck Displacement Devices

Figure 5.36: Plan View of Horizontal Cap Beam Displacement Devices 5.2.2.2 Vertical Displacement of Girders/Superstructure

5.2.2.2.1 Phase 1

It was important to obtain a relative vertical displacement profile for the superstructure and girders in order to investigate the force path along the deck and the moment distribution between the girders. Therefore, string potentiometers were mounted between the bottom side of the flanges of the designated girders and the strong floor, as shown in Figure 5.37. Only half of the bridge was instrumented as shown in Figure 5.38. A string potentiometer was placed next to each actuator, located between the floor and the abutment, in order to verify the displacement readings provided by the actuator.

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Figure 5.37: Phase 1 Vertical Girder Displacement Device Locations

Figure 5.38: Locations of Vertical Displacement Devices along the Girder Length During Phase 1 of Testing

5.2.2.2.2 Phase 2

The vertical displacements of the girders were also measured during Phase 2 of the testing. However, since the expected displacements were larger than those for Phase 1, a combination of string and linear potentiometers with a larger stroke, as shown in Figure 5.39, replaced many of the potentiometers that were specified for Phase 1. It should be noted that, in order to reduce the setup time, the locations of the potentiometers were the same and one set of potentiometers was removed. Additionally, the same girders that were instrumented for Phase 1 were instrumented for Phase 2.

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Figure 5.39: Phase 2 Vertical Girder Displacement Device Locations 5.2.2.3 Column Curvature and Growth

The curvature of the column, mostly within the plastic hinge regions, was recorded by placing a series of four linear potentiometers, spaced at 6 in. on center, along the extreme tension and compression fibers of the column, as shown in Figure 5.40. An additional linear potentiometer was mounted along the length of the column on both its East and West sides in order to measure any longitudinal column growth.

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Figure 5.40: Column Curvature and Growth Device Locations 5.2.2.4 Cap Beam Twist and Dilation

The angle of rotation due to torque acting along the length of the column, between girders, was measured via rotation devices placed at the midpoint between girders and along the centerline at the bottom of the cap beam, as shown in Figures 5.41 and 5.42. The sensitivity of these devices needed to be high, as the expected rotations are relatively small. Linear potentiometers were also placed between the rods, to which the rotation devices were mounted, in order to measure the dilation of the cap along its longitudinal axis. Since the column interfered with the linear potentiometers running along the length of the cap beam, the rods and linear potentiometers in the vicinity of the column were placed on the top of the cap beam as shown in Figure 5.41. Only half of the cap beam was instrumented in this manner, again due to symmetry. Additionally, a rotation device was mounted to the rod directly above the column in order to measure the rotation of the cap beam. Finally, a rotation device was placed on each end of the cap beam in order to further measure any twist.

Linear Pot: 1 in (+/-) Stroke Linear Pot: 1 in (+/-) Stroke [1/2 in compression, 1 1/2 in tension] Rods Spaced at 6 in o.c.

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Figure 5.41: Profile View of Cap Beam Twist and Dilation Instrumentation Scheme

Figure 5.42: Plan View of Cap Beam Twist and Dilation Instrumentation Scheme 5.2.2.5 Connection Rotation and Neutral Axis Depth

Similar to the strain gauge plan, the instrumentation within the connection region was critical. A linear potentiometer was mounted on the underside of the superstructure spanning the connection between the girder and the cap, as shown in Figure 5.43. A rotation device was also mounted on the rod that was embedded in the girder and used in mounting the aforementioned linear potentiometer. Together, the linear potentiometer and the rotation device were used to

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determine the neutral axis and rotation of the connection at each girder. One center, intermediate, and exterior girder on each side of the cap was instrumented in this manner.

Figure 5.43: Girder-to-Cap Beam Connection Instrumentation Scheme 5.2.2.6 Girder Curvature

The linear potentiometers at the bottom of the girders, as detailed in the previous section, were also used to determine the curvature of the girders near the connection region. An additional linear potentiometer was placed along the bottom of the girder away from the connection. A second linear potentiometer was placed at the top of the girder, directly above the additional pod that was added to the bottom. A third linear potentiometer was placed above the girder and spanned the interface between the girder and cap beam. These details are shown in Figure 5.43. One center, intermediate, and exterior girder on each side of the cap received this instrumentation.

5.2.2.7 Lateral Displacement Measurement Between Girders

Since some lateral displacement between the girders was observed during the preliminary finite element analysis of the superstructure, string potentiometers were placed between girders

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at a distance of 16 ft from the center of the cap beam, as shown in Figure 5.44. Both the center and one of the interior girders as well as one of the interior and exterior girders received this configuration. The lateral displacement between girders was only measured on the as-built side of the connection.

Figure 5.44: Lateral Displacement between Girders Device Locations 5.2.2.8 Improved Connection Strand Slip

As noted previously, the untensioned strands that were used in the improved connection detail were incorrectly terminated at the face of the diaphragm on the as-built connection side of the bent cap. However, this did have one benefit, in that it allowed any slip of the strands to be measured. One strand directly East of the center girder and one strand directly East of the West intermediate girder were therefore mounted with a linear potentiometer in order to measure any strand slip. The potentiometers were mounted to the strand via a circular clamp around the strand, which then measured any displacement relative to the face of the diaphragm, as shown in Figure 5.45.

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Figure 5.45: Strand Slip Device Location 5.2.2.9 Footing Movement

In order to ensure that the footing did not experience any displacement during the testing, one linear potentiometer was placed between the footing and the floor in the push direction. An additional linear potentiometer was placed perpendicular to the loading direction on each side of the footing. These linear potentiometers were placed diagonally from each other in order to detect any torsion in the footing as well, as shown in Figure 5.46.

The uplift of the footing was also monitored by placing a linear potentiometer on the North and South side of the footing, which was mounted to the floor as a point of reference, as shown in Figure 5.47.

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Figure 5.46: Footing Displacement Device Locations

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