2. Experimental Test Program

2.1 Experimental Test Program

The experimental test programs used for the wide beams and deep beams were similar. All of the beams were ramp loaded with a point load at mid-span using hydraulic actuators. Slip between the wood and concrete layers, was measured at the locations of the shear notches. Vertical deflections of the beam were measured at selected locations along the span. The deep beam load test setup is shown below in Figure 2.1. All of the measurements were taken using string potentiometer transducers (Figures 2.1 and 2.2). Both the wide beams and the deep beams were repeatedly ramped up to various load levels using the hydraulic actuators in stroke control.

Measurements were recorded at different levels along the ramp load tests. The 91.48 cm (3 ft.) wide beams with 6.10 m (20 ft.) spans (cast in March 2001) were tested in May and June of 2001. The 60.98 cm (2 ft.) wide beams with 6.10 m (20 ft.) spans (cast in March 2001) were tested in July and August of 2003. The deep beams (cast in March 2001) were tested in February and April of 2002.

2.2 Conduct of the Tests - Deep Beam Specimens

Each of the two deep beam specimens was tested in same load frame using the same equipment. First, a simple support was built at each end of the 3.63 m (143") clear span. A cylindrical steel bar sandwiched between two steel plates was used to provide a roller support at one end. At the other end of the span a steel half-cylinder, with a thin steel plate on top, was bolted down to a rigid support to simulate a pin type support. The beams were rolled into place on the frame with care taken to not allow the beams to bend under their own weight. After configuring the beam to the load frame the specimen was then instrumented. Small holes were drilled into the concrete shear notches. Then a plastic anchor was fitted in each hole and glued in place with epoxy. Eye-screws were screwed into the plastic anchors and string potentiometers were attached to them. String potentiometers were then mounted on a bracket that was then attached to the wood layer of the beam with screws. For deflection measurements of the beam, string potentiometers were placed underneath the beam at the 1/3, 1/2, and 2/3 points along its span. String was used to attach the string potentiometer cables to eye-screws screwed into the bottom of the beam.

Before initiating the load tests all notch connectors were re-tightened to 70 N-m (51.63 lb-ft) using a torque wrench. This was done to close the gaps that had formed between the concrete and wood layers due to shrinkage. A single point load was applied through the use of two hydraulic rams connected with a distributor beam loading a steel half cylinder placed at mid-span of the simply supported 3.63 m (143") span. Table 2.1 includes the details of the tests conducted for each deep beam specimen. Deep beam 1 was subjected to six load tests, designated DB1.1 through DB1.6. In order of occurrence, these tests consisted of, five cycles each from 0 to 35.58 kN (8 kips) and back to zero; then 10 repetitions, each from 0 to 35.58 kN (8 kips) and back to zero; then 10 repetitions, each from 8.89 kN (2 kips) to 35.58 kN (8 kips) and back to zero; then a failure ramp load test from 0 to 61.55 kN (13.84 kips); and a final post-failure ramp load test from 0 to 81.22 kN (18.26 kips). Deep beam 2 was subjected to four load tests, designated DB2.1 through DB2.4. In order of occurrence these tests consisted of, five repetitions each from 0 to 35.58 kN (8 kips) and back to zero; then eight repetitions from 8.89 kN (2 kips) to 35.58 kN (8 kips) and back to zero; then a failure ramp load test from 0 to 87.65 kN (19.71 kips); then a final post-failure ramp load test from 0 to 80.96 kN (18.2 kips).

Table 2.1 Deep Beam Load Tests

2.3 Conduct of the Tests - Wide Beam Specimens

The four wide beam specimens were cast into place on the load frame in which they were tested. Figure 2.2 shows the setup of the load frame, string potentiometer transducers, and the position of the hydraulic actuator. The beams were moved into place for testing by carefully sliding the specimens along their supports. The simple supports for the beams were made using steel bars placed between two steel plates. A pin support was made at one end of the span by welding the steel bar in place, while at the opposite end the bar was left free to roll. The span for each of the Wide Beams was 6.1 m (20 ft.). Each beam was loaded at mid-span using the single actuator pressing against a thick square steel distributor plate. Instrumentation for the wide beams was installed in the same manner as for the deep beam specimens. The locations of the string-potentiometers varied between two sets of beams. For wide beams 1 and 2, deflection measurements of the beam were taken at the 1/4, 1/2, and 3/4 points along the span. For wide beams 3 and 4, deflection measurements were taken at the 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, and 7/8 points along the span. For each of the four beams interlayer slip measurements were taken at all of the six notches on one side of the beams.

All the wide beams were subjected to two repeated ramp load tests, one starting at 0 load and the other starting from a non-zero load level. Before the tests all the notches were tightened with a torque wrench to 70 N-m (51.63 lb-ft). Table 2.2 shows the starting and ending load levels for each of the eight load tests. Wide beams 1 and 2 were subjected to five load repetitions from 0 to 177.92 kN (40 kips), then eight load repetitions from 44.48 (10 kips) to 177.92 kN (40 kips). Wide beams 3 and 4 were subjected to eight load repetitions from 0 to 88.96 kN (20 kips), then eight load repetitions from 22.24 kN (5 kips) to 88.96 kN (20 kips).

Table 2.2 Wide Beam Load Tests