As background to a theoretical investigation to establish tentative recomendations on maximum safe lengths and skew angles for concrete and steel skewed bridges with integral abutments, a survey of the highway departments of all 50 states was made to obtain information on the design and performance of skewed bridges with integral abutments. The findings of the survey are summarized, including various design criteria and limitations being used; typical pile orientations being used in bridge design by the different states and types of analysis used for thermal expansion and contraction; assumptions being made regarding selected design parameters; specific construction details being used, such as approach slab, backfill, and pile cap; long-term performance of skewed bridges with integral abutments; and previous research on skewed bridges with integral abutments. The variation in design assumptions and length limitations among the various states in their approaches to the use of integral abutments is discussed. The problems associated with thermal-induced abutment movement and the solutions developed by the different states for most of the ill effects of abutment movement are summarized. In view of the lack of theoretical and experimental research in this area, it is hoped that the survey will provide some useful empirical experience and information on the design of skewed bridges with Integral abutments.

The routine use of integral abutments to tie bridge superstructures to foundation piling began in the United States about 30 years ago (.!,-!). Kansas, Missouri, Ohio, and Tennessee were some of the early users. This method of construction has steadily grown more popular. Today, more than half of the state highway agencies have developed design criteria for bridges without expansion joint devices. Most of the states that use integral abutments began by building them on bridges less than 100 ft long. Allowable lengths have been increased based on good performance of successful connection details. Full-scale field testing and sophisticated rational design methods were not commonly used as a basis for increasing allowable lengths. This led to wide variations in criteria for the use of integral abutments from state to state. In 1974, the variation in the criteria between Kansas and Missouri was 200 ft (.!,). A survey conducted by the University of Missouri in 1972(~) indicated that allowable lengths for concrete bridges with integral abutments were 500 ft in some states and only 100 ft in others. Continuous steel bridges with integral abutments in the 300-ft range have performed successfully for years in such states as North Dakota, South Dakota, and Tennessee. Continuous concrete structures 500-600 ft long with integral abutments have been constructed in Kansas, California, Colorado, and Tennessee t § ). In Iowa, the maximum bridge length for which integral-abutment construction is allowed