: A comprehensive tool on The Engineering Community that includes reinforced concrete calculations and standard CAD templates for wing walls and reinforcement details.
No. For high fills (>20ft), the structure behaves as a deep buried pipe. You need finite element software (e.g., SAP2000 or PLAXIS). The rigid frame assumption fails due to soil-structure interaction. box culvert design calculations xls link
: Sites like The Engineering Community and ExcelCalcs provide downloadable templates for both single and multi-cell designs. : A comprehensive tool on The Engineering Community