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OCR for page 58
58 around 0.008 in. wide. The end zone cracks extend for about oped Table 3.15 to provide decision criteria for acceptance 30 in. from the face of the member end. No signs of shop and repair of web end cracking during production. repair could be detected by the research team. Although no These criteria were developed based on observation of inspection reports were made available by the precast producer the results of structural testing of eight full-scale girders for review by the research team, it was clear that no repair and field inspection of five bridges. The investigation shows was made to the end zone cracks. that There was no deficiency of shear, bond, or flexural capac- 3.5.4 Bridge Field Inspection Conclusions ity attributed to end zone cracking whether the cracks were Based on the field inspection conducted on five bridges in filled or not prior to testing. Nebraska and Virginia, the study team made the following The epoxy repaired end of one of the Washington girders conclusions: did not exhibit any improvement in load carrying capacity over the unrepaired end. Thus, if epoxy repair is desirable, Of the five bridges inspected in Nebraska and Virginia, four it should be intended only to seal the cracks, not to restore bridges were built over water channels where the ambient air tensile capacity of the repaired surface. is humid. Field inspection of these bridges did not reveal any No signs of efflorescence or corrosion due to web end crack- signs of reinforcement corrosion or concrete delamination, ing were reported in the inspected Virginia and Nebraska although end zone cracking had existed at the time of pre- bridges. stress release. No cracks wider that 0.01 in. were observed, even in the Comparing the crack widths at the time of inspection with cases where end zone reinforcement was extremely light those documented in the inspection reports revealed no (#4 at 12 in.) and the prestressing force is relatively large deterioration. (sixty-two 0.6-in. diameter strands). There is no NDOR or VDOT policy that specifically requires Most observed crack lengths from this study and from pre- field inspection reports to document end zone bursting vious reports were limited to about 36 in. cracks, regardless of whether they had been reported in plant inspection reports. Also, there was no consistency in girder End zone cracking is quite different from flexural cracks in identification between the producer's and the owner's iden- conventionally reinforced beams and slabs, and from tensile tification systems. Thus, it was difficult for the research team cracks in water storage structures. Even if one equates these to gain much value from field inspection reports. These con- cracks with flexural cracking, the 0.012-in. width is less than straints reduced the researchers' effort to recording cracks in the 0.013 in. and 0.016 in. used in early versions of the ACI-318 the field without fully correlating them with cracks at the Building Code for exterior and interior exposures, respectively. plant before the girders were shipped. It corresponds to the "z" value of 130 kip/in. that was pre- There was no documentation relative to methods and viously used in AASHTO specifications to indirectly con- materials used to repair end zone cracking. trol crack width in environments with severe exposure. Specification of crack width limits and "z" value limits for flexural design have been dropped from recent editions of 3.6 Manual of Acceptance, Repair, the ACI-318 Building Code and from the AASHTO speci- or Rejection fications. This was done due to evidence that flexural crack- ing, which is normal to the flexural reinforcement, does not Based on the information collected from field inspection correlate to reinforcement corrosion. Thus, it is quite rea- in Nebraska and Virginia, and the results of the structural sonable to limit end zone cracking to 0.012 in., without testing of eight full-scale girders, the research team devel- need for any repair. Table 3.15. Decision criteria for acceptance and repair of web end cracking during production. Criterion Crack Width (in.) Action 1 Less than 0.012 No action 2 0.012 to 0.025 Fill the cracks and apply surface sealant to the end 4 ft as recommended in this report 3 0.025 to 0.05 Fill cracks with epoxy and apply surface sealant to the end 4 ft as recommended in this report 4 Greater than 0.05 Reject girder, unless shown by detailed analysis that structural capacity and long-term durability are sufficient