The bevel is sometimes introduced at the inlet of box culvert to decrease the flow contraction at the inlet. In fact, the outlook of bevel is similar to a chamfer except that a chamfer is smaller in size and it is mainly used to prevent damage to sharp edges of concrete during construction. The bevels can be designed as plane or round edges.
The addition of bevels to the inlet of box culverts could increase the capacity of box culvert by about 5-10%. In fact, the socket end of precast concrete pipes serves the same function as the bevels in the box culvert.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
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why fillet is neccssary inside the rcc box culvert.