The National Academies Press

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Pages 7-23

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From page 7... ... 7 A review of the history of provisions for fatigue design and evaluation of bridges was performed in order to identify specific provisions that can be improved, as well as to identify items that need to be researched further so that new provisions handling such items can be included. An effort was also spent in reviewing fatigue evaluation provisions of other countries in order to compare and contrast with existing provisions. Read the entire page →
From page 8... ... 8The fatigue life estimate also accounts for the growth in truck traffic volume. In the LRFR Manual, the correlation is made to the average lifetime daily truck traffic for a single lane. Read the entire page →
From page 9... ... 9 Eurocode Specification The Eurocode (2005) has been revised since its first version reviewed in NCHRP Report 299 by Moses et al. Read the entire page →
From page 10... ... 10 Summary of Identified Fatigue Expert Survey Results A short questionnaire was sent out to identified fatigue experts in order to gain useful information and opinions. The first question inquired about recent test data that may be useful for revising Section 7 of the Manual. Read the entire page →
From page 11... ... 11 (and Article 3.5 in the Guide) recommends an approximation using the chart in Fig. Read the entire page →
From page 12... ... 12 negative remaining life (also as an estimate) Read the entire page →
From page 13... ... 13 for some older riveted structures that may have literally hundreds of tack welds that may need to be ground off otherwise. The survey sent out to state Departments of Transportation contained two questions specifically addressing tack welds. Read the entire page →
From page 14... ... 14 Lack of Guidance for the Evaluation of Distortion-Induced Fatigue Cracks The AASHTO MBE (2011) indicates that distortioninduced fatigue is more of a stiffness problem (or lack thereof) Read the entire page →
From page 15... ... 15 the transverse connection plate weld toe than at the lateral gusset plate weld toe. Second, for an in-plane stress range of 41.4 MPa (6 ksi) Read the entire page →
From page 16... ... 16 However, no guidance is provided on how to evaluate or retrofit details that have developed distortion-induced fatigue cracks. Additional information is needed on how to evaluate details susceptible to distortion-induced fatigue cracking. Read the entire page →
From page 17... ... 17 of the connection in a line perpendicular to the fasteners. It is well known that welds are significantly more ductile when they are oriented parallel to the direction of the loading rather than perpendicular to the load. Read the entire page →
From page 18... ... 18 of the specimen fitted into the hydraulic grips along with the entire test setup is shown in Figure 7. Distortion-Induced Fatigue Tests One problematic condition that has not been well studied is the retrofit details for connections that exhibit distortioninduced cracking. Read the entire page →
From page 19... ... 19 induced fatigue cracking. Other than the experimental results reported by Fisher et al. Read the entire page →
From page 20... ... 20 Figure 9. Top and side view of subcomponent test specimen. Read the entire page →
From page 21... ... 21 in order to speed up the time required for testing, two test setups were used. A schematic of Test Setup 1 is shown in Figure 10. Read the entire page →
From page 22... ... 22 measured clip gage reading, and thereby control relative distortion of the web gap between the stiffener and the flange. In order to evaluate the effectiveness of the clip gage in measuring the distortion of the stiffener, Linear Variable Differential Transformers (LVDTs) Read the entire page →
From page 23... ... 23 loading is continued until failure or completion of 5,000,000 loading cycles. At this point, the specimen is removed in order to examine any fatigue cracks to determine if the retrofit was effective in significantly slowing or halting further fatigue crack growth. Read the entire page →

From page 7...

... 7 A review of the history of provisions for fatigue design and evaluation of bridges was performed in order to identify specific provisions that can be improved, as well as to identify items that need to be researched further so that new provisions handling such items can be included. An effort was also spent in reviewing fatigue evaluation provisions of other countries in order to compare and contrast with existing provisions.