Live Load Effect in Reinforced Concrete Box Culverts Under Soil Fill.

摘要

Live load effects in box culverts generally diminish with soil fill thickness. In addition, the effect of the live load may be nearly negligible compared to the dead loads when significant fill is placed above the crown of the culvert. The objective of this study is to determine the effects of live load (truck loads) on bridge-size (spans greater than 20 ft) reinforced concrete box culverts under soil fills of different thickness. The study considered the field testing of 10 existing reinforced concrete box culverts with fill depths ranging from 2.5 feet to 13.5 feet. Instrumentation of the culvert consisted of 12 reusable strain transducers and 12 LVDTs. The instrumentation was designed to be applied, used, and removed in one day of testing. Loaded trucks were driven over the culvert to provide live load. The results of the testing show that live load effect does diminish with increasing fill depth. The AASHTO LRFD and LFD Standard Specifications were both overly conservative in predicting strains and displacements compared to the field data for fill depths less than 8 feet At above 6 feet of fill the measured effect of the live load was less than 10% of the dead load effect. This could be considered as a point at which to ignore the live load effect and therefore not load rate the culvert.