Tham khảo tài liệu 'inspection, evaluation and repair of hydraulic steel structures episode 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | EM 1110-2-6054 1 Dec 01 Figure 8-12. Cracked girder tension flange at diaphragm of a lift gate 3 Repair alternatives. a The ideal crack repair would also improve the fatigue strength of the detail and would eliminate the out-of-plane distortion. However to eliminate the displacement shown in Figure 3-5 would require significant structural modification and the cracking might not have occurred given connection details with higher fatigue strength. The fatigue strength of the detail would be improved by providing a smooth radius between the diaphragm flange and girder flange. This would improve the stress concentration condition and could theoretically improve the fatigue strength from Category E to Category B see condition 16 of Table 2-1 . The recommended repair is a combination of crack repair procedures shown in Figures 8-3 and 8-4. First repair the crack according to Figure 8-4 while following the guidelines for welded crack repair given in paragraph 8 -4a. Then add the radius plate and drill the hole as shown in Figure 8-3 and as described in paragraph 8-6a 3 . b Another possible alternative would be to install a bolted repair similar to that shown in Figure 8-7 a similar repair is described in paragraph 8-6c 3 . Before the bolted repair is installed the crack tip should be drilled and the diaphragm-flange-to-girder-flange weld should be removed to eliminate the stress concentration. c In the design of new gates the low fatigue strength details could be eliminated by installing a skin plate on the downstream face of the gate. This was done in a recent design of a vertical lift gate. Instead of downstream bracing members the new design called for a skin plate on the downstream face of the gate. g. Crack in vertical lift gate at uncoped web stiffener. 1 Description of condition. A through-thickness crack that extends through the tension flange of a built-up girder on a vertical lift gate is shown in Figure 8-13. The structure had been in service for less than 2 .
