A Comparison of AASHTO Bridge Load Rating Methods (2011) / Chapter Skim
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Pages 84-92
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From page 84... ...
84 Following are conclusions and suggestions that can be drawn based on the review of the analysis results shown in this report and in the appendices: • No clear trends based on the sorting criteria checked, i.e., year of construction, girder spacing, skew angle and span length, could be identified. • A significant percentage of the girders that passed rating under the LFR and produced rating factors below 1.0 for the LRFR were controlled by criteria that were not checked under the LFR method of rating.
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From page 85... ...
85 6A.4 -- LOAD-RATING PROCEDURES 1.4.A6CnoitcudortnI -- 1.4.A6 Three load-rating procedures that are consistent with the load and resistance factor philosophy have been provided in Article 6A.4 for the load capacity evaluation of in-service bridges: • Design load rating (first level evaluation) • Legal load rating (second level evaluation)
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From page 86... ...
86 ADTT = 1000 1.65 1.30 ADTT 100 1.40 Linear interpolation is permitted for other ADTT. • Reduce the reliability index from the design level to the operating (evaluation)
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From page 87... ...
87 If a bridge is located on a low volume route, say ADTT <100, it is unlikely that more than one truck will exist on the bridge at the same time. In such cases, a single lane loaded distribution factors may be appropriate when evaluating routine or annual permits.
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From page 88... ...
88 ………………………………………….. 1.4.5.A6CgnitaRdaoL-ngiseD -- 1.4.5.A6 The Strength I load combinations shall be checked for reinforced concrete ……………… Service III need not be checked for HL-93 at the Operating level as Service III is ……………… ………………………………………………………… …..
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From page 89... ...
89 Service limit states are mandatory for the rating of segmental concrete bridges, as specified in Article 6A.5.13.5. b2.2.4.5.A6CgnitaRdaoLtimreP -- b2.2.4.5.A6 The provisions of this Article are considered optional and apply to the Service I load combination for reinforced concrete components and prestressed concrete components.
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From page 90... ...
90 visible signs of shear distress need not be checked for shear when rating for the design load or legal loads. In order to eliminate the possibility of being more conservative when rating for permit vehicles than when rating for design loads, the evaluation for shear under permit vehicles is limited to the cases where the factored load effects from the permit vehicles exceed that from the design load.
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From page 91... ...
91 Rating for the shear friction provisions of the AASHTO LRFD at the interface between a concrete beam and the concrete deck is not required. The literature does not include cases of distress due to shear friction failure along the interface between a concrete beam and the deck.
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From page 92... ...
92 (category C or lower) a rating factor for infinite fatigue life should be computed.
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