Although the State of Nebraska alone spends about $2.50 million annually on construction of reinforced concrete box culverts, relatively little research has been devoted to them in recent years. The research described in this paper was, in part, directed at establishing the state of the art of the design of these culverts. Specifically, a summary is given in this paper of the results of recent field measurements. It has been found that the field measurements of soil pressures indicated higher pressures than those given by the American Association of State Highway and Transportation Officials (AASHTO) specifications. The responses of state bridge engineers, or those with similar responsibilities, to a questionnaire on their design practices are reported herein. Several inconsistencies in the AASHTO specifications were reported. Despite these inconsistencies and the apparent under estimation of soil loading, very little structural distress was observed. Lack of distress may be attributed to several causes. For example, some of the states use higher soil pressures than AASHTO's specified values. Also, the conservative criteria associated with the working stress design increase the margin of safety against failure and reduce the effect of under estimating the soil loads.
Abstract