1、Section 6 CULVERTS 6.1 CULVERT LOCATION, LENGTH, AND WATERWAY OPENINGS Recommendations on culvert location, length, and waterway openings are given in the AASHTO Guide on Hydraulic Design of Culverts. 6.2 DEAD LOADS Vertical and horizontal earth pressures on culverts may be computed by recognized or
2、 appropriately documented analytical techniques based on the principles of soil me- chanics and soil structure interaction, or design pressures shall be calculated as being the result of an equivalent fluid weight as follows. 6.2.1 Culvert in trench, or culvert untrenched on yielding foundation A. R
3、igid culverts except reinforced concrete boxes: (1) For vertical earth pressure- 120 pcf For lateral earth pressure- 30 pcf (2) For vertical earth pressure-120 pcf For lateral earth pressure- 120 pcf (1) For vertical earth pressure-120 pcf For lateral earth pressure- 30 pcf (2) For vertical earth pr
4、essure-120 pcf For lateral earth pressure- 60 pcf For vertical earth pressure- 120 pcf For lateral earth pressure- 120 pcf B. Reinforced concrete boxes: C. Flexible Culverts: When concrete pipe culverts are designed by the Indirect Design Method of Article 16.4.5, the design lateral earth pressure s
5、hall be determined using the procedures given in Article 16.4.5.2.1 for embankment installations and in Article 16.4.5.2.2 for trench installations. 6.2.2 Culvert untrenched on unyielding foundation A special analysis is required. 6.3 FOOTINGS Footings for culverts shall be carried to an elevation s
6、ufficient to secure a firm foundation, or a heavy rein- forced floor shall be used to distribute the pressure over the entire horizontal area of the structure. In any location subject to erosion, aprons or cutoff walls shall be used at both ends of the culvert and, where necessary, the entire floor
7、area between the wing walls shall be paved. Baffle walls or struts across the unpaved bottom of a culvert bar- rel shall not be used where the stream bed is subject to ero- sion. When conditions require, culvert footings shall be reinforced longitudinally. 6.4 DISTRIBUTION OF WHEEL LOADS THROUGH EAR
8、TH FILLS 6.4.1 When the depth of fill is 2 feet or more, concen- trated loads shall be considered as uniformly distributed over a square with sides equal to 1% times the depth of fill. 6.4.2 When such areas from several concentrations over- lap, the total load shall be uniformly distributed over the
9、 area defined by the outside limits of the individual areas, but the total width of distribution shall not exceed the total width of the supporting slab. For single spans, the effect of live load may be neglected when the depth of fill is more than 8 feet and exceeds the span length; for multiple sp
10、ans it may be neglected when the depth of fill exceeds the dis- tance between faces of end supports or abutments. When the depth of fill is less than 2 feet the wheel load shall be distributed as in slabs with concentrated loads. When the calculated live load and impact moment in concrete slabs, bas
11、ed on the distribution of the wheel load through earth fills, exceeds the live load and impact moment calculated according to Article 3.24, the latter moment shall be used. 6.5 DISTRIBUTION REINFORCEMENT Where the depth of fill exceeds 2 feet, reinforcement to provide for the lateral distribution of concentrated loads is not required. 6.6 DESIGN For culvert design guidelines, see Section 16. 181
