Detailed information is provided in the followings. But to proceed in this design, we will adopt the pressure from the tandem system. Also, the 2019 CANDE Tool Box, a companion program useful for load rating, is freely available to download. All cells are assumed the same size, and the clear opening dimensions remain constant during the design process. L 2 = 1.2 + 0.4m + 1.2m = 2.8 m (Spacing of wheels + contact length + depth of fill)ī 2 = 2.0 m + 0.4m + 1.2m = 3.6 m (Spacing of wheels + contact length + depth of fill)Īs can be seen, the difference between considering the entire tandem system and one wheel alone is not much. BRASS-CULVERT designs, analyzes, and/or rates one-, two-, three-, or four-cell reinforced concrete box culverts with prismatic members (precast or cast-in-place) with or without a bottom slab.
When considering the tandem system as shown in Figure 10 This is considered in the lateral and longitudinal directions.įig 10: Overlapping Tandem Axle Load Dispersion Through Earth Fill It is acknowledged that the pressure from each wheel in the axles can overlap when considering the tandem system as shown in the figure below. Therefore, the equivalent uniformly distributed load from each wheel to the culvert is A little consideration will show that this is not so far away from the 2:1 load increment method.įig 9: Single Wheel Load Distribution Through Compacted Earth Fill However, clause 4.9.1 (Note 1) of EN 1991-2:2003 recommends a dispersal angle of 30° to the vertical for a well compacted earth fill. Understanding hydraulics and hydrology is a necessity for designing drainage structures such as culverts that control the. Photo: Corey Haeder, Cretex Concrete Products West, Inc.
This is the method recommended by BD 31/01, otherwise, Boussinesq’s method can also be used. FHWA and SDDOT recently conducted a study of various inlet section configurations for box culverts with the goal of updating industry design software and coefficients. We are going to disperse the load through the earth fill to the box culvert by using the popular 2(vertical):1(horizontal) load increment method.