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OCR for page 35
35 Figure 3.38. Bottom flange during cutting. Figure 3.40. End zone cracking extending the full length of the web. the specimens were shipped to the structures laboratory in Omaha, Nebraska, for testing. the full section, before the bottom flange was separated from the rest of the section. When the bottom flange was cut away from the web, the web was no longer able to oppose these 3.3.3 Preparation of the Test Specimens forces, and the bottom flange cracked. Figure 3.38 shows the The team's objective was to find the most suitable method bottom flange while being cut from the web. Although there of testing the cracked and repaired ends for tensile capacity, was a great deal of cracking, the section remained intact, as and to compare them with the capacity of the uncracked zone shown in Figure 3.39. in the mid-length of the specimen. This was done by cutting When the beam was cut, the full extent of the interior out sections of the web, turning them over on their sides, and cracking became visible, as shown in Figure 3.40. Upon loading each section as if it were a beam. inspection, it was clear that the epoxy did not totally fill the The top and bottom flanges were cut away, leaving only cracks as anticipated. From the cut section, the epoxy could the webs of each girder. The thickness of the web required only be seen entering approximately 0.2 in. into the crack, two cuts of the saw, one on each side of the web, as shown in as shown in Figures 3.41 and 3.42. Also, visual inspection Figure 3.38. The bottom flange contained a large prestress- revealed a lack of adhesion between the concrete and the ing force in the 32 strands. This force had been resisted by epoxy. length of penetration of epoxy seal Figure 3.39. Bottom flange completely cut from Figure 3.41. End zone cracking extends vertically the specimen. and horizontally.