movement. That results in a reduction of the lateral expansion which is obvious by the

lower recorded strain.

 Measured Rotations

 Four tilt meters were used to measure the rotations of the beams. The rotations for

both the control and tube beams at increasing loads are reported in Table 4-5. The

measured rotations of the control beam were lower that the measured rotations of the tube

beam for the same amount of load. That was due to the CFRP grid tubes improving the

resistance of the tube beam against rotation. The differences in rotation grew as the load

increased from approximately 20% for a load of 21.9 kips to approximately 25% for a

load of 109.1 kips.

Table 4-5. Rotations measured by tilt meters
Beam Load Tilt Tilt Tilt Tilt
 (kips) meter T1 meter T2 meter T3 meter T4
 (degrees) (degrees) (degrees) (degrees)
 Control 21.9 -0.1377 -0.1209 -0.1244 -0.1528
 43.7 -0.2979 -0.2660 -0.2628 -0.3240
 65.6 -0.4705 -0.4239 -0.4100 -0.5066
 87.3 -0.6530 -0.5942 -0.5749 -0.7011
 109.1 -0.8590 -0.7987 -0.7735 -0.9144
 148.0 -1.3169 -1.2593 -1.2236 -1.3776
 Tube 21.9 -0.1080 -0.0943 -0.0977 -0.1218
 43.7 -0.2350 -0.2089 -0.2045 -0.2511
 65.6 -0.3685 -0.3283 -0.3176 -0.3868
 87.3 -0.5106 -0.4595 -0.4456 -0.5326
 109.1 -0.6678 -0.6136 -0.5948 -0.6894
 152.8 -1.0527 -1.0000 -0.9724 -1.0675

 The rotations of the two beams based on the displacement profiles were also

calculated by fitting a 6th order polynomial curve to the displacement profiles and then

taking the first derivative of the polynomial equation. The calculated rotations for the

same loads and locations are presented in Table 4-6.