Evaluation of moment equation in the 2000 Canadian highway bridge design code for soil–metal arch structures

Abstract

This paper evaluates the moment equation in the 2000 Canadian highway bridge design code (CHBDC) for soil–metal arch structures. This equation is adopted from Duncan's moment equation (1978), which is based on his finding from finite element analyses that the maximum moment occurs at the quarter point of soil-metal structures. However, finite element analyses carried out for this study demonstrate that the maximum moment in soil–metal arch structures with spans greater than approximately 11 m occurs at the crown point. In this study, the location and magnitude of the maximum moment was examined for soil–metal arch structures having spans of 6–20 m under three construction stages; backfill up to the crown, backfill up to the cover depth, and live loading. Based on the location of the maximum moment, two sets of moment equations dependant on span length were found necessary. Moment coefficients and moment reduction factors in moment equations are proposed from the results of numerous finite element analyses for semi-circular arch and part-arch types of soil–metal structures considering the various design variables, such as span length, structural shapes, section properties, and backfill conditions. The validity of the coefficients and reduction factors in the moment equation of the 2000 CHBDC is investigated by comparison with those proposed in this study. The comparison demonstrates that the moment equation of the 2000 CHBDC is still valid and a little conservative. The effects of design variables on the variations of moments of soil–metal arch structures during construction stages are also examined.Key words: soil–metal arch structures, moment equations, CHBDC, soil-structure interaction.