Structural Response of a Low-Fill Box Culvert under Static and Traffic Loading

Box structures have been commonly used under highways. They are installed at grade or at great depths. When a box culvert is buried at a shallow depth, vertical pressure and dynamic impact due to traffic loading transferred onto the roof of the culvert can induce deflections of the culvert. The effect of the traffic load on the response of the culvert depends not only on the magnitude, pattern, and speed of the traffic load but also on the pavement structure. To investigate these factors, a reinforced concrete box culvert under three roadway sections (concrete pavement, concrete shoulder, and unsurfaced fill) was tested under static and traffic loads. The total thickness of pavement layers was 0.65 m within the pavement section and decreased gradually towards the end of the culvert through the shoulder and the unsurfaced section. The culvert was instrumented with displacement transducers under the roof and pressure cells on top of the roof within the unsurfaced fill. A low-boy truck with a known axle configuration and load was used to apply seven static load combinations and traffic loads at different speeds. Deflections under the roof and pressures on the roof were measured. The test results show that the magnitudes of the deflections of the culvert roof under static loads were generally increased from the concrete pavement, the concrete shoulder, to the unsurfaced fill. The truck at a higher speed generally induced more deflections than that at a lower speed or stationary.